How to melt glass in a muffle furnace - technology, melting point, features

Almost every material and compound in the world has three possible states: solid, liquid and gas. Under normal conditions, materials exist in different states, which depend on their chemical properties.

To unbalance them, it is necessary to increase or decrease the temperature to the specified value. For example, the melting point of glass starts at about 750 degrees Celsius. The material has so-called amorphous properties, which is why it has no specific meaning.

It all depends on the quantitative and qualitative composition of impurities in the compound. So it is possible to establish a specific value for a selected item only experimentally. To do this, you will need a certain set of measuring instruments, which are available only in specialized laboratories. You can, of course, take household analogues, but they will have too large an error.

What is glass?

Glass is a homogeneous amorphous substance obtained by solidification of a melt of oxides. Glass may contain three types of oxides: glass-forming, modifying and intermediate . Glass-forming oxides are silicon, boron, phosphorus, germanium, and arsenic. Modifying oxides, the introduction of which lowers the melting point of glass and significantly changes its properties, include oxides of alkali (Na, K) and alkaline earth (Ca, Mg, Ba) metals. Intermediate are the oxides of aluminum, lead, titanium, and iron. They can replace part of the glass-forming oxides. The glass-forming frame of glass is a continuous spatial lattice, at the nodes of which ions, atoms or groups of atoms are located. The chemical composition of glass can be varied within wide limits. Therefore, the properties of glass may be different.

Based on the chemical composition, depending on the nature of the glass-forming oxides, silicate, aluminosilicate, borosilicate, aluminoborosilicate and other types of glass are distinguished.

Depending on the content of modifiers, glass can be alkaline or alkali-free.

Based on their purpose, they distinguish between construction (window, glass blocks), household (glass containers, dishes) and technical (optical, electrical, chemical, etc.) glass.

The structure and properties of glass are determined by its chemical composition, melting, cooling and processing conditions.

Glass is a thermoplastic material; when heated, it gradually softens and turns into a liquid. Melting occurs in a certain temperature range, the value of which depends on the chemical composition of the glass. Below the glass transition temperature Tg, glass becomes brittle. For ordinary silicate glass Tc = 425 – 600°C. Above the melting point, glass becomes a liquid. At these temperatures, glass melt is processed into products.

The density of glass is 2.2 – 8.0 g/cm3. High-density glass contains significant amounts of lead and barium oxides.

Glass is a tough, solid, but very fragile material. Glass has good compression resistance (= 400 – 600 MPa), but is characterized by low tensile strength (30 – 90 MPa) and bending (50 – 150 MPa) tests. Alkali-free and quartz glass are more durable.

The mechanical properties of glass are enhanced by thermal and chemical treatment. Thermal tempering of glass consists of heating it to temperatures close to the softening point and rapidly uniformly cooling the surface in a stream of air or oil. At the same time, compressive stresses arise in the surface layers, and the strength of the glass increases by 2–4 times. For the manufacture of devices operating at high pressure, safety glass – triplex – is used.

Triplex is a combined glass consisting of two or more tempered layers glued together with a transparent elastic film. Chemical treatment consists of etching the surface layer with a solution of hydrofluoric acid to destroy surface defects. An even greater effect is achieved with combined chemical and thermal treatment.

The most important property of glass is transparency in the wavelength range of visible light. Ordinary sheet glass transmits up to 90%, reflects about 8% and absorbs about 1% of visible light. Ultraviolet rays are almost completely absorbed by window glass.

Glass has high chemical resistance in aggressive environments (with the exception of hydrofluoric acid and alkalis). Water gradually destroys glass due to the formation of alkaline solutions. The higher the temperature and concentration of alkaline oxides in the glass, the stronger the effect of water. Glass as a technical material is widely used in various fields of technology and the national economy. This is explained by a favorable combination of physicochemical and mechanical properties, the ability to change these properties over a wide range depending on the composition of the glass and methods of thermal exposure, as well as the ability of glass to easily lend itself to various methods of hot and cold processing.

Quartz glass, consisting of almost pure silica (99% SiO2), is of two types, depending on the production method: optically transparent and opaque. Quartz glass differs from all known glasses in its high physical and chemical properties: high heat resistance (1400°C), low temperature coefficient of linear expansion [(0.5 – 0.55)•10 -6 K -1 ], high thermal (withstands extremes temperatures 800 – 1000°C) and chemical resistance, especially to the action of acids (except hydrofluoric acid) and water. Quartz glass has high dielectric characteristics and is transparent in the visible, ultraviolet and partially infrared regions. Quartz glass, which has particularly high thermal and chemical resistance in combination with a low temperature coefficient of linear expansion, is used for the manufacture of crucibles, thermocouples, electric vacuum products, chemically resistant containers, pipes, and laboratory glassware. To protect parts from corrosion at temperatures up to 500–600°C, glass enamels are used in mechanical engineering.

Foam glass is produced by foaming liquid glass mass at high temperature due to the introduction of gaseous substances - crushed limestone, chalk, coal. Foam glass has low density, low thermal conductivity and is characterized by high sound absorption. It is a non-flammable, heat-resistant and chemically resistant material.

Glass-crystalline materials (ceramics) are obtained from glass by its complete or partial crystallization. The name “ceramics” is formed from the words “glass” and “crystals”. Citales are sometimes called glass ceramics. The content of the crystalline phase in glass ceramics can be up to 95%. The crystal size usually does not exceed 1 – 2 microns.

Sitalls are dense, opaque, gas-tight, rigid and hard materials. Their mechanical strength is 2–3 times higher than the strength of glass. They resist abrasive wear well. The combination of a low thermal coefficient of linear expansion and high mechanical strength gives them high heat resistance. Citales are characterized by high chemical resistance to acids and alkalis and are not susceptible to corrosion when heated to high temperatures. Sitalls do not absorb moisture at all.

Thanks to the combination of lightness, strength, hardness and manufacturability, glass ceramics are widely used in mechanical engineering. They are used to make sliding bearings that operate without lubrication at temperatures up to 550°C, pistons and exhaust parts of internal engines, chemical equipment, spinnerets for drawing synthetic fibers, impellers and blades of pumps pumping aggressive liquids with abrasives. Sitalls are used as heat- and wear-resistant enamels to protect metal parts. Sitall enamels can work at temperatures up to 800 – 900°C.

Manual and tabletop glass burners (review)

Classification of glass burners

Glass burners (gas glass burners) are used to heat glass products to change their shape in accordance with the purpose of the product and ensure that the product performs its intended functions.
They are used for all types of work related to glass processing in glass-blowing workshops and industrial enterprises. During operation, a mixture of combustible gas (natural gas or propane-butane) with an oxidizer is supplied to the glass blowing burner, which is used as oxygen contained in the ambient air and pure oxygen, including in a mixture with compressed air.

More detailed information on combustion of gases and oxidizers is presented in Appendix 01.

Click! Click and application 01 will open!

Combustion is a rapid chemical reaction of combining flammable components with oxygen, accompanied by intense heat release and a sharp increase in temperature.

Combustion reactions are described by stoichiometric equations that characterize qualitatively and quantitatively the substances that enter into the reaction and the substances formed as a result of it.

The combustion reaction of any hydrocarbon can be expressed by the following general equation:

CmHn + (m+n/4)O2 = mCO2 + (n/2)H2O + Q

where m is the number of hydrocarbon atoms in a hydrocarbon molecule; n is the number of hydrogen atoms in the same molecule; Q is the amount of heat that is released during combustion (heat of combustion).

The amount of heat that is released during the combustion of gases used in gas burners is given in Table 01.
Table 01. Heat of combustion of flammable dry gases at 0°C and 760 mmHg.

The data given in table. 01 can be used to calculate the heat output of the burner.

The thermal power of the burner is calculated as the product of the hourly gas consumption and its calorific value.

The calculation is made using the formula

Nkw = (0.278) x Vn x Q

where NkW is the burner power in kW; Vn—nominal volumetric gas flow rate in m3/hour; Q is the heat of combustion of gas, given in table. 01, in mJ/m3

In practice, the volumetric gas flow rate for a specific burner can be obtained by direct measurements using a rotameter (flow meter).

From the data in Table 01 and the above formula it follows that with the same consumption of combustible gas, the thermal power of a propane burner is almost 9 times higher than the thermal power of a hydrogen burner. And from the laws of physics it follows that the faster we want to heat a specific body to a certain temperature, the greater the power of the source of thermal energy, in this case the burner, must be.

In further calculations, the amount of air and gas will be determined in normal cubic meters - nm3

A normal cubic meter is a non-systemic unit of measurement for the amount of a substance that, in a gaseous state, occupies one cubic meter under conditions called “normal conditions” (pressure 760 mm Hg, which is 101325 Pa, and temperature 0 ° C)

The heat of combustion of complex gases consisting of several components (for example, a mixture of propane and butane) is determined by the chemical composition of the gas and the heat of combustion of the components, kcal/Nm3:

Q0°,760) = (1/100)(r1Q1 + r2Q2 + ... + rnQn) (1)

where r1, r2 + . . . + rn is the percentage of components in the complex gas.

In practical conditions of gas combustion, oxygen for combustion is supplied with air (as its component).
The composition of dry air, excluding small amounts of carbon dioxide and rare gases, is taken as indicated in Table 02 Table 02. Composition of dry air in%

Therefore, 1 m3 of oxygen is contained in 4.76 m3 of air.

The combustion reaction of any hydrocarbon in air is expressed by the equation

CmHn + (m+n/4)(O2 + 3.76N2) = mCO2 + (n/2)H2O + (m+n/4)3.76N2

where m is the number of hydrocarbon atoms in a hydrocarbon molecule; n is the number of hydrogen atoms in the same molecule;

The oxygen and air requirements during the combustion of various gases, calculated from combustion reactions, are presented in Table 03.
Table 03. Theoretical demand for dry oxygen and air Volume of gas combustion products at α = 1.0

The actual air consumption in nm3 per volume of gas in nm3, due to imperfect mixing of fuel and oxidizer during the combustion process, is taken to be slightly higher than the theoretical one

Vfact = Vtheor x α

where Vfact is the actual air flow; Vtheor - theoretical air flow, presented in the table above; α is the excess air coefficient.

Coefficient α, depending on the quality of mixing of gas and air, is taken to be in the range of 1.05-1.2.

Under real gas combustion conditions, the excess air coefficient α should always be greater than one, since otherwise there will be incomplete combustion of the gas.

For a complex gas, the theoretical flow rate of dry air can be calculated using an equation based on the oxygen demand of individual components, nm3/nm3 of gas:

Vtheor = (4.76/100)(0.5H2 + 0.5CO + 2CH4 + 3.5C2H6 + 5C3H8 + 6.5C4H10 + 3C2H4 + 4.5C3H6 + 6C4H8 - 02) (2)

The theoretical flow rate of moist air is greater than that calculated by formula (2) by the volume of water vapor contained in it, nm3/nm3.

Vm = Vtheor(1 + 12.4x10-6dv) (3)

where dв is air humidity, g/nm3; 12.4x10-6 - volume of 1 g of water vapor in nm3.

Below are examples of gas combustion calculations

EXAMPLE 1.

Let us determine the heat of combustion of 1 nm3 of dry natural gas of the following composition: CH4 -97%, C2H6 - 2%, C3H8 - 0.3%, C4H10 - 0.2%, CO2 - 0.2% and N2 - 0.3%

Solution:

Using the data in Table 01 and formula (1), we determine the heat of combustion of gas

Q = 85.5 ⋅ 97 + 152 ⋅ 2 + 218 ⋅ 0.3 + 288 ⋅ 0.2 = 8720 kcal/nm3

EXAMPLE 2.

Let us determine the air requirement in nm3 for complete combustion of 1 nm3 of natural gas having the composition indicated in example 1. Air temperature tair = 20 °C; relative humidity φ = 0.6; excess air coefficient α = 1.1.

Solution:

The theoretical dry air flow rate is calculated using formula (2)

Vtheor = (4.76/100)(2 ⋅ 97 + 3.5 ⋅ 2 + 5 ⋅ 0.3 + 6.5 ⋅ 0.2) = 9.7 nm3/nm3

The content of water vapor in the air at tair = 20 °C and φ = 0.6; equals:

ds = 17.3 ⋅ 0.6 = 10 g/Nm3

The calculation took into account that air at a temperature of 20 °C can accumulate a maximum of 17.3 g of water vapor.

The theoretical flow rate of moist air is determined by formula (3).

Vm = 9.7+ 0.00124 x 10 x 9.7 = 9.82 g/Nm3

Actual humid air flow at α = 1.1:

Vfact = 9.82 x 1.1 = 10.8 nm3/nm3

Those. for complete combustion of 1 nm3 of natural gas, 10.8 nm3 of air is required (taking into account its natural humidity) and with a recommended excess air coefficient of α = 1.1

The main types of glass blowing burners can be classified according to the following characteristics:

1. By type of burner
   1.1 stationary
2. 1.2 manual
3. By type of flammable gas
   2.1 burners for natural gas
4. 2.2 burners for propane-butane
5. 2.3 universal burners (without restrictions on the type of gas)
6. By type of oxidizing agent
   3.1 air
7. 3.2 compressed air
8. 3.2 pure oxygen
9. 3.3 mixture of compressed air and pure oxygen
10. According to the method of supplying the oxidizer
    4.1 atmospheric (injection) burners
11. 4.2 burners with forced compressed air supply
12. 4.3 burners with pure oxygen supply
13. 4.4 burners with simultaneous supply of compressed air and pure oxygen
14. According to the method of mixing gas with oxidizer
    5.1 without premixing
15. 5.2 with full premix
16. 5.3 with incomplete premixing
17. By type of torch.
    6.1 with one flame
18. 6.2 with double flame

Stationary burner

(pos. 1.1) is mounted on the work table. Changing the direction of the torch is ensured by a hinge system through which the burner head is connected to the fastening unit. Processing is carried out by moving the product relative to the burner.

Manual burner

(pos. 1.2) does not have any mounting on the desktop. Changing the direction of the torch is ensured manually. Processing is carried out mainly by moving the burner relative to the product.

Natural gas burner

(item 2.1) uses methane (CH4) as a fuel gas. In addition to methane, natural gas includes its closest homologues: ethane, propane, butane. The methane content in natural gas is at least 80%.

Burner for propane-butane

(item 2.2) uses a mixture of propane (C3H8) and butane (C4H10) as a combustible gas. In this case, the propane content in the combustible gas is at least 75%.

Universal burner

(pos. 2.3) uses both natural gas and propane-butane as fuel gas.

Oxidizer air

(pos. 3.1) is used when the oxygen in the atmospheric air is sufficient for complete combustion of the flammable gas. Used in burners with low fuel gas consumption.

Oxidizer compressed air

(pos. 3.2) is used when increasing the supply of flammable gas, when the oxygen in the atmospheric air is not enough for complete combustion of the flammable gas.

Oxidizer pure oxygen

(pos. 3.3) is used in burners with high consumption of combustible gas.

Oxidizer mixture of compressed air and pure oxygen

(pos. 3.4) is used when it is necessary to reduce the temperature of the burner flame, but also ensure complete combustion of the combustible gas. Therefore, in such burners the consumption of combustible gas is set lower than in the previous case.

Atmospheric burner

(pos. 4.1) uses combustion air from the environment, which enters the burner through holes in its body due to suction (injection) of combustible gas, which exits at high speed from the injector nozzle located inside the burner.

Burner with forced compressed air supply

(pos. 4.2) uses compressed air for combustion, supplied from a compressor or other device that provides the compressed air pressure necessary for the gas burner.

Burner with pure oxygen supply

(pos. 4.3) uses pure oxygen to burn flammable gas. To supply oxygen to the burner, pressurized oxygen cylinders are mainly used, but sometimes in case of low oxygen consumption by the burner (up to 0.5 m³/hour), oxygen concentrators are used.

Burner with simultaneous supply of compressed air and pure oxygen

(pos. 4.4) uses a mixture of compressed air and pure oxygen to burn flammable gas. In this case, compressed air supplied to the burner is used to dilute the combustion products and lower their temperature.

Burner without premix

(pos. 5.1), in which flammable gas and oxidizer are mixed behind the outlet openings of its nozzle.

Full premix burner

(pos. 5.2), in which combustible gas and oxidizer are mixed in the burner body in front of the outlet openings of its nozzle.

Partial premix burner

(pos. 5.3), in which the combustible gas is partially mixed with the oxidizer up to the nozzle outlets and partially mixed with the oxidizer behind the nozzle outlets.

Single flame burner

(pos. 6.1) has a nozzle that forms a torch consisting of one flame.

Double flame burner

(pos. 6.2) has a nozzle that forms one double flame torch, with each flame supplied with its own combustible gas and oxidizer and both flames are located symmetrically relative to the central axis of the nozzle.

General notes on the operation of glass burners

Taking into account the above classification of glass blowing burners, when using the latter, the following must be taken into account.

To perform glassblowing operations, various adjustments of the burner are used - both in terms of the qualitative composition of the mixture of combustible gas with air (or oxygen), and in terms of the quantity of the mixture.

When choosing a glass blowing torch with one or another type of oxidizer, it is necessary to proceed from the fact that the amount of oxygen, whether it is part of atmospheric or compressed air or in its pure form, is determined by the amount of combustible gas consumed by the burner. So, for the complete combustion of one liter of methane, according to the chemical reaction of its combustion, 2 liters of pure oxygen or 10 liters of atmospheric air are needed. The combustion of one liter of propane requires 2.5 times more oxygen than the complete combustion of methane. It should be taken into account that with an increase in the amount of combustible gas consumed by the burner, its thermal power increases and, conversely, with a decrease in the consumption of combustible gas, the thermal power of the burner decreases.

The use of compressed air in glass burners produces a lower temperature flame compared to burners that use pure oxygen as an oxidizer. A low-temperature flame is obtained because the air has a high percentage of inert gases, which do not take part in combustion, but sharply reduce the temperature of the gas flame. Therefore, in order to ensure the versatility of the glass blowing torch, i.e. the possibility of using it to heat both soft (with a low softening temperature) and hard glass (with a high softening temperature) along with oxygen, compressed air is also supplied to the burner. By changing the oxygen-air ratio in the oxidizer, you can regulate the temperature of the burner torch within a wide range.

More detailed information on supplying additional air to the burner is discussed in Appendix 02.

Click! Click and application 02 will open!

In practice, the following combustion temperatures of gases in a burner are distinguished: heat output, calorimetric, theoretical and actual.

Heat output

is defined as the temperature of the products of complete combustion of combustible gases under adiabatic conditions with an excess air coefficient α = 1.0 at a gas and air temperature t = 0°C.

Calorimetric temperature

combustion differs from heat output in that the gas and air temperatures, as well as the excess air coefficient α are taken at their actual values.

Theoretical temperature

combustion is determined similarly to the calorimetric temperature, but adjusted for the endothermic reactions of dissociation of carbon dioxide and water vapor. For glass-blowing burners and gas burners, the theoretical combustion temperature is almost equal to the calorimetric temperature.

Actual temperature

combustion products are below the theoretical combustion temperature and depends on the amount of heat loss to the environment, the degree of heat transfer from the combustion zone by radiation and other heat losses.

The calorimetric combustion temperature of natural gas) and technical propane in air at a temperature of 0 ° C with a humidity of 1%, depending on the excess air coefficient, is given in Table 04.
Table 04. Theoretical (calorimetric) combustion temperature depending on the excess air coefficient α

As follows from the data presented in the table, dilution of combustion products with excess air (with increasing α) leads to a decrease in the theoretical combustion temperature of the fuel.

The obtained result can be explained if we consider the combustion reaction of hydrocarbons in air, for example, propane.

The propane combustion equation has the form: (see Appendix 01)

C3H8 + 5O2 + 18.8N2 = CO2 + 4H2O + 18.8N2

Nitrogen does not participate in the combustion reaction, but when heated, it carries away a significant amount of heat from the combustion zone. It is clear that the more nitrogen in the flame, the more heat is carried away and the temperature of the flame should fall with increasing nitrogen.

The volume of nitrogen supplied to the combustion zone, together with air, is determined by the formula;

VN2 = 0.79αVm + 0.01N2

where VN2 is the volume of nitrogen; α - excess air coefficient; Vm is the theoretical dry air flow.

Thus, with an increase in the excess air ratio, the volume of nitrogen supplied to the combustion zone increases and, consequently, more heat is removed from the combustion zone and, as a result, the combustion temperature decreases.

In practice, it is necessary to know not only the theoretical combustion temperatures given above, but also the maximum temperatures that occur in the flame.
Their approximate values ​​are usually determined experimentally using spectrographic methods. The maximum temperatures occurring in a free flame at a distance of 5–10 mm from the top of the conical combustion front are given in Table 05. Table 05. Maximum flame temperature depending on the type of oxidizer

Since glassblowing burners usually do not use either acetylene or hydrogen, it follows from the table that the flame temperature of glassblowing burners with propane is higher than that of burners with methane for any type of oxidizer, although the differences are not significant (no more than 3%).

When glassblowing works, burners are used without preliminary mixing of combustible gas with the oxidizer (hereinafter referred to as external mixing burners) and burners with preliminary mixing of the specified gaseous media (hereinafter referred to as internal mixing burners), as well as burners of incomplete internal mixing.

External mixing burners (Fig. 1) are the most convenient for adjusting flame parameters. In these burners, the combustion gas and the oxidizer pass through the burner separately from each other. So oxygen passes through the burner through many capillaries, the outlets of which (ports) are located on the outer surface of the nozzle. As a result, gas and oxygen mix behind the burner outlets.

The number of ports in the burner can reach several dozen. The shape and temperature of the flame and its width depend on how many ports there are in the burner and how they are placed relative to each other. It is this factor, as well as the choice of material for the nozzle and burner head, that is how burners of different models differ from each other.

Fig.1 External mixing burner

The advantages of this type of burner include the presence of a very calm, soft, wide flame, which is easy to adjust and, most importantly, for soft glasses (sodium-lime-silicate glass, as well as lead glass), the technical characteristics of the flame for burners of this type are more preferable than the flame of internal mixing burners.

In addition, external mixing burners do not have flame penetration into the burner and the flame is less noisy compared to internal mixing burners.

Many types of colored glasses, especially opaque ones, lose their original color when heated in internal mixing burners, and the character and degree of color change, up to gray. As already mentioned, the flame characteristics of external mixing burners are well regulated and in these burners you can easily obtain a neutral flame, i.e. a flame in the torch of which there is no excess of either flammable gas or oxygen, which allows, when processing colored glass, to preserve its original color.

With internal mixing burners (Fig. 2), the combustible gas and oxidizer are mixed inside the burner. Since these burners do not have any pipelines or capillaries inside their body for supplying gas media to the nozzle openings, these burners are simpler to manufacture and relatively cheaper compared to external mixing burners.

Fig.2 Internal mixing burner

Internal mixing burners work well with hard borosilicate glass, but as stated above, they are not very good with soft glass. At the same time, the flame of internal mixing burners is narrower and has a slightly higher temperature and is noisier than that of external mixing burners.

When choosing a burner, always pay attention to the number of inlet fittings for gas media. Burners with three or more inlet fittings are capable of providing the flame temperature necessary for processing almost any type of glass.

Based on the above, when choosing a burner, it is necessary to take into account that if the burner is designed to work only with hard borosilicate glasses, then it is enough to have only an internal mixing burner. If a glass blowing torch is needed to work with both hard and soft glass, as well as colored glass, then you should have an external mixing torch.

When choosing external mixing burners for professional work, burners with three or more inlet fittings for gas media are more preferable.

When deciding which burner you need to purchase for glassblowing, you should also take into account that it is easier to get a small flame with a large burner than with a small burner to get a larger flame. On a small burner, in order to heat the glass to a higher temperature, you need to bring the burner torch as close as possible to the surface of the glass, and this can melt and burn the glass.

At the same time, a larger flame provides more heat to heat the glass without making the flame more intense. In addition, a larger flame covers a larger surface of the glass and therefore the glass will not cool quickly when moving from one glass processing area to another adjacent area. And rapid cooling of glass can lead to internal stresses and, as a result, to cracking.

Some of the burners discussed below have a separate central low-wattage internal mixing flame that can be used without the large high-heating output external mixing flame surrounding it. This allows you to get flames of various shapes and sizes on the burner.

Types of glass blowing burners

This section describes the main types of glass burners sold on the domestic market.

By clicking on any picture or model name in the table, you can go to a detailed technical description of the burner.

Fig.3 Teklu burner

To work with glass, in most cases, gas burners are used, mainly of the tabletop type. To ensure heating of the glass, a mixture of flammable gas (methane or propane) with an oxidizer, which is used as oxygen contained in the ambient air and pure oxygen, is supplied to the burner.

Fig.4 Mecker burner

To work with so-called soft fusible glass (for example, soda-lime-silicate glass), the operating temperature of the burner flame should be in the range of 800-1100 degrees. Celsius. For this purpose, when working with thin-walled glass of small diameter (glass tubes with a diameter of up to 10 mm and a wall thickness of no more than 1 mm), which do not require high burner power (for example, work on sealing ampoules), you can use Teklu burners (Fig. 3) or Mecker burners (Figure 4). These burners have a maximum power of about 1200 W and oxygen from the surrounding air is sufficient for their operation. Detailed technical characteristics of these burners are given on the websites “Teklu Burner” and “Mekera Burner”.

The attached video shows the production of glass capillaries on a Mecker burner

Making glass capillaries using a Mecker burner

To heat soft glass tubes with a diameter of up to 30 mm and a wall thickness of up to 1 mm or more, a burner of higher power is required than the above-mentioned Teklu and Mekera burners. To do this, a burner with a higher consumption of combustible gas is used and air under pressure is supplied to the burner for its complete combustion. Such a burner is shown in Figure 5 (model ST-33).

Fig.5 Gas+air burner mod.ST-33

The left fitting is for forced air supply, and the right one is for supplying flammable gas. This external mixing burner has a power of up to 4 kW with a maximum flame temperature of 1700 degrees. Celsius. The total number of ports for this burner for gas and air is 42. Detailed technical characteristics of the burner and a description of the design are available on the website page “burner for glass mod.33”.

If glass processing requires a higher operating temperature of the burner flame, then use burners that supply pure oxygen instead of air. Such a burner is shown in Figure 6 (model ST-80). This is an external mixing burner.

Fig.6 Gas+oxygen burner mod.ST-80

The upper fitting is designed to supply flammable gas, and the lower one is intended to supply oxygen. This burner has a power of up to 3.3 kW. but gives a flame with a maximum temperature of 2200 degrees Celsius. Has seven ports for oxygen and seven ports for flammable gas. Detailed technical characteristics of the burner and a description of the design are available on the website page “burner for glass mod.80”.

To ensure operation of a gas burner with any type of glass, both soft and hard, it is necessary that the temperature of the burner flame can be adjusted within a wide range. To do this, gas, oxygen and air are supplied to the burner simultaneously.

In this case, during operation, two flames burn in the burner, independent of each other. One of them is the central main internal mixing flame, into which flammable gas and oxygen are supplied, around which a second additional external mixing flame is formed, for which oxygen is used (supplied through capillaries), flammable gas and air.

Such a double-flame burner in one torch is shown in Fig. 7 (model ST-32).

Fig.7 Double flame gas+oxygen+air burner mod.ST-32

This burner has three inlet fittings. The left fitting is used to supply oxygen, the middle one is for air supply and the right one is for supplying flammable gas. The burner has four control valves for oxygen and air and one control valve for gas supply.

The upper left control valve is used to regulate the oxygen supply to the central nozzle (main flame), the upper right one is used to regulate the gas supply to the same nozzle.

To adjust the parameters of the additional flame, the burner has separate control valves from the above, one for oxygen supply (located on the side on the left) and the second for compressed air (located on the side on the right) and a valve for adjusting the supply of combustible gas (located on the side on the right).

Oxygen is added directly to the combustible gas and air environment at the burner outlet to ensure complete combustion of the combustible gas. In this case, additional oxygen is evenly distributed over the entire surface of the nozzle, entering through a larger number of capillary holes located on the surface of the nozzle around the central nozzle of the additional flame.

The ST-32 burner has 37 ports, of which 15 are for the main flame and 22 ports are for the additional flame.

This burner provides smooth adjustment of the operating flame temperature within the range of 1100-2600 degrees. Celsius with burner power up to 10 kW. However, greater burner power also requires greater consumption of oxygen and fuel gas compared to burners of other models. Detailed technical characteristics of the burner and a description of the design are available on the website page “burner for glass mod.32”.

To ensure savings in oxygen and fuel gas, in addition to the three inlet fittings, like the ST-32 burner, two more fittings are added for separate supply of oxygen and gas to the central nozzle. This allows the latter to be used as a pilot burner for an additional flame.

Such a burner has five fittings for supplying gas media, arranged in two rows and is shown in Fig. 8 (model ST-03).

Fig.8 Burner with igniting flame gas+oxygen+air mod.ST-03

In the first row there are fittings for oxygen, air and flammable gas, gas media into which are supplied through a gas media saving device mod.C1, details of which are given below.

Oxygen and gas are supplied to two fittings located in the second row directly from sources of gas media for the main flame, which burns constantly when the burner is operating.

Detailed technical characteristics of the burner and a description of the design are available on the website page “burner for glass mod.03”.

According to the main technical characteristics, the ST-03 burner with the S-1 device is similar to the ST-32 burner, but has an important advantage - significantly lower oxygen and gas consumption.

A similar burner (with five inlet fittings), but with a power of up to 25.5 kW, is shown in Fig. 9 (model ST-02). This burner has 37 ports for the main flame and 114 ports for the auxiliary flame. There are 151 ports in total.

Fig.9 High power gas+oxygen+air burner with igniting flame mod.ST-02

Detailed technical characteristics of the burner and a description of the design are available on the website page “burner for glass mod.02”.

To reduce the consumption of combustible gas, oxygen and air by gas burners, which use, in addition to the main flame, an auxiliary (igniting) flame, a device for saving the consumption of gaseous media mod. C-1 (economizer), which is shown in Fig. 10.

Fig. 10 Gas saving device (economizer) mod. S-1

A description of the device for saving gas media is given on the corresponding “website page”.

When using the device in its original position, only the ignition flame of the burner burns. When you press the foot pedal, the main burner flame ignites.

A hand torch is one of the most important tools for a glassblower. With it he performs a number of operations - from melting the ends of a cut tube to soldering and bending. The burner should be as light and small as possible to make it easier to handle. This problem has been successfully solved in the mod burner. ST-21R.

The manual glass blowing torch ST-21R with incomplete internal mixing, shown in Fig. 11, is designed for processing solid borosilicate glass and can burn natural gas or propane-butane along with oxygen and air. The burner has four control needle valves, one for gas and air and two for oxygen, some of the oxygen is mixed with the combustible gas inside the burner, and some outside it. Optimal setting of the burner model ST-21R allows you to achieve a flame temperature of up to 2800 °C with a maximum power of about 4 kW.

Fig. 11 Manual three-wire torch ST-21P

A detailed description of the burner is presented on the website page “manual three-wire glass blowing burner mod.ST-21R”.

Another model of manual glass blowing torch is also used. This is a ST-22 burner. The burner is similar in technical parameters to the ST-33 burner. Used for working with soft soda-lime glass or lead glass. Maximum temperature 1700°C. Maximum thermal power 4 kW. Compressed air is used as an oxidizer. No oxygen is used.

Fig.12 Manual gas+air burner ST-22

A detailed description of the burner is presented on the website page “manual glass blowing burner mod.ST-22”.

When working with softened glass, in addition to a gas torch, a glassblower must have a set of reamers for processing the ends of tubes, holes, making flanges, and also giving the softened glass the necessary shapes and configurations.

Set R-11 contains 11 standard sizes of reamers of 4 shapes, shown in Fig. 12. This kit provides the glassblower with the necessary tools of this type to perform almost any type of work.

Fig.12 Set of reamers P-11

A detailed description of the composition of the set of reamers R-11 is presented on the website page “Set of reamers for glass blowing works R-11”.

In conclusion, we present a summary table of gas consumption for the above burners for one hour of continuous operation.
By clicking on the model name you can go to its detailed description. Gas consumption for glass burners

When using the table, it must be taken into account that 1 kg of propane-butane produces 0.535 m³ of vapor, and when propane-butane is burned in a burner together with oxygen, the maximum flame temperature of 2850ºC is achieved with a ratio of propane-butane vapor to oxygen equal to 1.42 m³/m³ . A further increase in this ratio does not increase the flame temperature, and with a decrease in the oxygen supply, the flame temperature decreases and at a ratio of 1.3 m³/m³ the flame temperature will be 2700ºC and at a ratio of 1.27 m³/m³ the flame temperature will be 2600ºC.

Similar data for the combustion of natural gas (methane) with oxygen are equal: with a gas-oxygen ratio of 1.18, the maximum flame temperature is 2780ºC, and with a ratio of 1.1 we will have 2600ºC.

Procedure for purchasing burners

The procedure for purchasing all of the above-mentioned glass burners can be found on the corresponding “How to buy” page of the website.

Burners are shipped from a warehouse in Moscow to all regions of the Russian Federation.

The material for this article was provided by.

Author F.A. Bronin

All rights reserved.

When using materials from this site partially or fully, a link to or to the author of the publication is required.

Properties of glass

Besides the fact that glass has a melting point and that a wide variety of products can be made from this material, it has many other properties. The density of glass largely depends on its chemical composition; this indicator characterizes the ratio of volume to weight of the material. So, this indicator is the lowest for quartz glass.

Crystal, on the contrary, has the highest, which can exceed 3 g/cm3. The strength of this material also depends on the chemical composition, that is, how glass can maintain its integrity in products under the influence of external loads. During tension and compression, the influence of the chemical composition is almost the same. The hardness of the material is affected by the presence or absence of impurities and their quantitative indicator in a given specimen. The hardest is considered to be the one that contains a large amount of silica, namely quartz and borosilicate. In turn, the presence of lead oxides in the composition reduces the strength characteristics. As you know, the high melting point of glass allows you to change its appearance and, if necessary, obtain a completely different shape. But at low temperatures, which are considered normal for human life, glass is destroyed under stress, rather than deformed.

The fragility of glass products depends on the thickness of the material, as well as the shape. The easiest way to break it into fragments is flat glass. To increase this indicator, magnesium oxides and boric anhydride are added to the composition during the production of the material. The more heterogeneous the glass, the more likely it is that it will break under mechanical stress.

Types of glass

If we temporarily ignore plexiglass and remember about other types of this material, then there are four of them: regular, quartz, borosilicate and crystal. Each species has its own special features that make it stand out from the rest.

Regular glass

Common glass includes soda glass, potash glass, and lime-sodium-potassium glass. The first type is used for the production of window glass, dishes, and various glass containers. Potash has a higher melting point. This type of glass is used to create high-quality tableware. This type of ordinary glass has a pronounced fade and transparency. The latter type is also actively used for the production of tableware.

Quartz glass

Quartz glass is produced by melting high purity raw materials. Therefore, the answer to the question at what temperature quartz glass melts is 1000°C. This demonstrates the fact that this type of material is also the most heat-resistant, so if you put it in hot water in cold water, it will not crack. Thanks to this, quartz glass can be used at very high temperatures, because to bring it into a liquid state, the temperature must reach 1500 ° C.

There are two varieties of this glass - transparent and milky-matte quartz. In terms of their performance, they are almost identical, but differ in optical properties. The surface of quartz glass has a greater adsorption capacity not only for moisture, but also for some gases. It is also worth remembering that quartz must be protected from all kinds of contaminants, including greasy hand marks; such stains can be removed with ethanol, or acetone can be used as an option.

Borosilicate glass

Borosilicate glass contains a large amount of boron oxide, which explains its name. Thanks to the introduction of this substance into the composition, it can be much stronger than other types. The resistance to thermal shock of borosilicate glass can exceed that of lime glass by 5 times. Other indicators are related to the chemical resistance of glass and allow its active use in electrical engineering. To soften this type of material described, it is necessary to heat it to a temperature of 585 ° C.

Crystal glass

Everyone is familiar with crystal; this material is considered the highest grade among various glasses; it not only has a unique shine, but also has the ability to strongly refract light. Crystal glass can be lead-containing or lead-free. The former have more weight and demonstrate a beautiful play of light; they are used to make dishes or souvenirs. Lead-free glass is more often used in optical instruments and is characterized by high quality.

Fire glass markings

Most of the information regarding the characteristics of fire glass can be found from its labeling. Letters of the Latin alphabet are used for designation:

• E – resistant to destruction;
• I – has high resistance to heating to a critical temperature;
• W – retains heat and does not allow heat to pass into the adjacent room.

The manufacturer guarantees the preservation of the declared characteristics for a certain time. Time in minutes is indicated after the letter marking. For a better understanding, you can consider examples:

• EIW 60 – the product is resistant to destruction, resistant to heat and retains heat for 60 minutes.
• EI 60 – resistant to destruction, prevents heating for 60 minutes.
• EI 30 – resistant to destruction, prevents heating for 30 minutes.

The characteristics and testing methods of fire-resistant fire-resistant glass are regulated by GOST-33000-2014.

Melting point of glass in degrees

For glass, due to its amorphous properties, it is quite difficult to single out a single melting point. Typically this indicator ranges from 750 to 2500 0 C.

The approximate temperature for the transition of bottle glass into a liquid state is 1200-1400 0 C, for quartz glass it is about 1665 0 C. Ampoule glass melts at 1550-1800 0 C, and liquid glass - at 1088 degrees Celsius. There is also plexiglass, the melting point of which is 160 0 C; due to its chemical composition, it cannot be fully classified as glass.

How to make glass?

Glass is produced by cooling molten components at temperatures between +300 and +2500 °C, at a rate sufficient to prevent the formation of visible crystals. Sand alone is enough to make glass, but the temperature required to melt it will be much higher.

Interesting materials:

What is the name of small smelt? What is the 180 degree meridian called? What is the name of the meridian from which geographic longitude is measured? What is the name of a month that has 31 days? What is the name of the place where the heroes of the story lived in bad society? What is the name of the place through which all people will pass on the Day of Judgment? What is the name of a place where there are a lot of plants? What is the name of the place where the mountain and hill begin? What is the name of the place where they print money? What is the name of the place where Gagarin landed?

Effect of temperature on glass melting

The melting temperature of glass deserves special attention. Despite the fragility of the material, in order to transform it into a liquid state, it will need to be heated to high temperatures. As for ordinary glass, its melting point ranges from 425 to 600 °C; for quartz glass, this figure reaches 1000 °C. Due to its fragility and, accordingly, the complexity of making really large parts from glass, there was a need to create a material that could be more durable while maintaining other properties. And in 1936, organic glass went on sale. The melting point of plexiglass is low, only 160 °C, and at 200 °C the material reaches a boil. Plexiglas is used literally everywhere, since its transparency is the same as that of others, but in terms of impact resistance it is an order of magnitude higher.

Environmental impact

The main environmental impact of glass production is due to the melting processes that release various gases into the atmosphere. For example, burning fuel or natural gas and decomposing raw materials results in the release of carbon dioxide.

Likewise, the decomposition of sulfates in batch materials produces sulfur dioxide, which promotes acidification. When nitrogen compounds decompose, nitrogen oxides are released, which contributes to acidification and the formation of smog. In addition, when raw materials and molten components evaporate, tons of particles are released into the atmosphere.

Other factors, such as emissions of volatile organic compounds and the generation of solid waste during production, also cause environmental problems.

However, recycled glass can solve many of these problems. It can be processed several times without significant loss of quality. Every 1,000 tons of glass recycled can result in a 300 ton reduction in carbon dioxide emissions and 345,000 kWh of energy savings.

On a smaller scale, recycling one glass bottle can save enough energy to power a 20-watt LED light bulb for an hour.

Although both production technologies have improved significantly in terms of efficiency, further reductions in emissions of dust particles, carbon dioxide and sulfur dioxide are still the main environmental challenges in flat glass production.

Principles for calculating melting point

Calculating the melting temperature of glass at home is a very difficult task. It will be associated with many difficulties, among which it is worth highlighting:

1. The need to ensure a gradual increase in the temperature of the molten body by strictly one degree. Otherwise, it will be impossible to reliably establish at what indicator the process of transition from solid to liquid begins, that is, the experiment will end in failure.
2. You need to find a very accurate thermometer that can measure temperatures up to 2 thousand degrees Celsius with a minimum error. The best option is an electronic device, which will be too expensive for home experiments.
3. Conducting an experiment at home, in principle, is not the best idea , because you will have to look for a container in which you can melt glass, get a stable source of fire that can provide the required level of heating, and buy expensive equipment.

Is it possible to melt glass and what is needed for this?

Glass melting is carried out at high temperatures. There is no exact value; it is determined experimentally. The heating time depends on what impurities and in what quantity are contained in the glass. Usually, for each specific type, the average values ​​of the melting temperature of glass are determined, which were obtained by studying and testing them in laboratories. The most common types melt at the following temperatures:

• Plain glass – 700-750 oC.
• Glass for making dishes and containers – 1200-1400oC.
• Ampoule – 1500-1800oC.
• Quartz – 1650°C.

At enterprises that work with glass, the temperature in the furnaces is maintained at 1600°C.

Bottle glass

There are two methods of melting glass - casting and bending. When casting, it melts to a liquid state and the necessary forms (molds) are filled with it. Bending is a process in which glass is heated to a viscous state and becomes bendable and pliable. In this state, glassblowers work with it, bending and stretching the material.

Glass bending

As you can see, the temperature of molten glass has high values, which can be achieved if you use a high-quality muffle furnace.

Furnaces for melting glass and their types

A muffle furnace is a device for uniform heating of substances. It consists of:

• Cases.
• A chamber, also called a muffle.
• Doors.
• Control unit.

The body can be made of stainless steel or carbon. Stainless steel models last much longer.

The muffle is the most important part of the furnace, because it is in it that the glass is melted and the heating elements are located. It can be made of ceramics, corundum or special fiber.

Another important part is the control unit, which is responsible for selecting the mode and setting the oven. Now all furnaces are equipped with electronic units, which have replaced dial units.

Furnaces also differ in their processing mode, they are:

• Operating in air (conventional).
• Vacuum (heating is carried out in a vacuum).
• Operating in a gas environment (heating is carried out in the presence of various gases, for example, hydrogen, nitrogen, argon, etc.).

There are models that are intended for home use, and there are professional units that are used in laboratories or large enterprises. Both domestic and foreign manufacturers produce various versions of muffle furnaces.

Features of using a muffle furnace using the example of melting bottle glass

You can melt a glass bottle at home with a regular muffle furnace on hand. Glass bottles are easy to find and come in a variety of shapes and colors. You can use containers for beer, juices, water, and cosmetics. Before you begin the process itself, they need to be carefully prepared. It is necessary to very carefully clean the bottles of stickers so that nothing remains on the surface. Then they need to be washed and dried so that there are no stains or greasy marks.

The melting degree of the glass from which the bottles are made is approximately 700-750°C. The oven must also be checked and cleaned before use. Next, the heating elements and the proper operation of the device must be tested using a pyrometric cone.

The rules for testing equipment are described in the operating instructions. Many ovens have special test programs that will help you find out if it is working properly.

To work you will need a shelf and a casting mold. They also need to be prepared and a special separating agent applied to separate the glass. The casting mold must be positioned so that it cannot flow beyond its boundaries. Next, you should set the desired temperature, which, as we have already said, depends on the type of glass and its chemical composition.

Melting bottle glass

The prepared bottle is placed in the center of the oven so that when melted it flows into the mold. Heating must be done gradually so that the casting mold does not crack. You need to set low initial values ​​and gradually increase them in small increments. At 500°C, bottle glass begins to melt, with the thin walls draining first. At this stage, you should try to heat the bottle evenly, increasing the temperature even more slowly. The glass will become liquid at 700°C, but the temperature should be increased by another 70°C and the liquid substance should be kept under these conditions for another 10 minutes. After this, it is necessary to perform an annealing operation. To do this, the resulting product is kept for a certain time at 500°C. This is necessary to ensure that the workpiece does not crack.

A furnace for melting glass is equipment with high temperatures, which has an increased hazard class, so when working with it you must adhere to safety regulations. Wear heat-resistant gloves and safety glasses.

Scope of application

Brands of heat-resistant glass are widely used in enterprises whose production processes involve high temperatures. The use of transparent material with good heat-resistant characteristics makes it possible to ensure continuous operation of components and assemblies, while guaranteeing the safety of operating personnel. Installing fire-resistant glass in doors and partitions separating production premises significantly reduces the likelihood of a fire occurring and spreading.

This material is also indispensable in everyday life, where there is high temperature, and it is impractical to use metal. A striking example is glass fireplace doors. It is convenient, a beautiful and functional fireplace will perfectly complement the interior of a residential building, it will also create an atmosphere of warmth and comfort. A door made of fireproof glass is beautiful and practical. It will not become a barrier to thermal radiation, while protecting the room from smoke and soot.

Fireproof glass can be found in the kitchen, among other things: kitchen apron, transparent doors of ovens and microwave ovens. Such solutions allow you to control the cooking process without having to open the door. Separately, we can recall the cooking surfaces of gas stoves; they allow you to distribute heat evenly, thereby helping to save energy resources.

Glass that is resistant to high temperatures is also used to make tableware. Transparent kitchen utensils are great for both open fire and oven cooking. Moreover, transparent dishes can be used in the microwave. An additional plus is that the glass surface is easy to clean.

Glass melting process

In laboratories, scientists find out the desired value through multiple experiments. The melting point of the glass is then entered into a table that also contains the chemical composition of the compound. This is necessary to understand which elements most influence melting, so that in the future this indicator can be brought to more or less standard characteristics.

The lack of a clear number forces production resources to be used irrationally. For example, in glass factories the temperature in furnaces is maintained at about 1600 degrees Celsius, despite the fact that many types could melt without problems at one thousand. Energy savings would significantly reduce the cost of finished products, which would have a positive impact on the economic efficiency of glass blowing factories.

The melting point of glass in degrees starts from 750 (some sources give a figure from 1000) and continues right up to 2500. Moreover, if you take acrylic glass, which in fact is not glass, but simply has that name, then it melts at only 160 degrees , and at 200 degrees it already begins to boil. But it consists of organic resin and does not contain silicon or other chemical elements.

But other brands, on the contrary, often boast a variegated variety of composition. The sand used in production is often insufficiently purified, resulting in a lot of unnecessary waste in the finished products. Outwardly, this does not affect the performance properties in any way, but leads to amorphous chemical characteristics.

A decrease in the melting temperature of glass can be achieved if appropriate elements are added to the melt. In household experiments, the most accessible are lead oxide and boric acid. The mass fraction will need to be calculated using known formulas, since it will depend on the amount of molten glass. After hardening, you can repeat your experiment and make sure that the material now melts at a much lower temperature.

But it is worth considering that the resulting glass has no practical value and is only suitable for experiments. This is due to the fact that the addition of impurities also changes its operating parameters, so that the substance will not be able to fully cope with the functions assigned to it. That is why no one changes the technological process by adding these components.

Basic values ​​for the transition of glass into a liquid state

Approximate values ​​for the transition of glass into a liquid state for some types:

– melting point of bottle glass – 1200-1400 degrees Celsius; – melting point of quartz glass – about 1665 degrees Celsius; – melting temperature of ampoule glass – 1550-1800 degrees Celsius; – liquid glass melting point – 1088 degrees Celsius.

For the last substance, you can indicate an exact figure, because it does not exhibit amorphous properties, since it is an aqueous alkaline solution of sodium and potassium silicates. It is also worth considering that glass does not melt immediately, but first turns into a viscous caramel-like state. This property is used by glassblowers to create various products and souvenirs.

You can do this craft at home. There will be no shortage of raw materials, since you can find a lot of glass bottles right on the street. And an ordinary gas lamp is also suitable as a device for softening the material. You can then sell your handmade products as souvenirs and earn good money.

Melting glass in industry

To produce glass, the first step is to prepare raw materials, which are mixed in certain proportions to obtain a homogeneous batch. This mixture is boiled in glass furnaces until a liquid and homogeneous glass mass is obtained.

The charge is melted in a furnace at a certain temperature, which depends on the chemical composition. The required temperature is achieved using fuel or gas burners. The high temperature is maintained for several hours so that the glass mass is cleared of air bubbles.

Scientists are conducting research to determine the melting point of different types of glass. They tabulate their results depending on the chemical composition of the compounds, and also work to increase the strength and change the properties inherent in the glass.

Float is a method used industrially to produce glass, invented by Pilkington back in 1959. Glass from the melting furnace enters a rectangular bath of molten tin, where it is cooled and then sent for annealing.

The industry uses glass melting furnaces that maintain temperatures at 1600 degrees Celsius. But this is not always justified, since many types of glass require temperatures of about 1000 degrees Celsius. Accordingly, maintaining a lower temperature will lead to the use of less fuel and cheaper production overall.

Fireproof glass in stoves and fireplaces

Fireplaces and open stoves are increasingly being installed in country houses and even in apartments.
An open fire decorates a room, but it can also cause a fire. Here you cannot do without fireproof glass. This is an excellent material for fire protection. It is used to create transparent doors that do not allow flames to enter the room, but not only that, modern design solutions allow you not to be limited to small glasses; you can easily create a unique transparent fireplace. Regardless of the size of the door or the scope of the project, installing fire-resistant glass into the metal frame of a stove or fireplace requires care and attention to detail. There are a number of recommendations that must be followed during the work process. When determining the linear dimensions of structural elements, it is necessary to take into account the difference in thermal expansion of materials. There must be a gap between the frame and the glass into which the fire-resistant cord is laid. When installing glass, it is necessary to ensure uniform pressure on it from all sides. Under no circumstances should you seal the joints; this may cause cracks to form.

Industrial glass melting equipment

The most important point for glass melting is the choice of furnace for glass production.

There are two types of classification of glass and glass furnaces. In the first case, ovens are divided into pot and bath ovens. In the second classification, the type of stove depends on the heating method. In this case, a distinction is made between flame, electric and gas-electric units.

Pot furnaces are most often used for small production volumes or for the production of special optical and lighting glasses.

Bath furnaces are large tanks of molten tin, over which the glass flows perfectly evenly. Tin helps to gradually cool the glass from 1600 0 C to 600 0 C, which avoids internal stress and does not impair the strength of the finished product.

Flame furnaces are the least efficient, with an efficiency of approximately 25-30%; smelting is carried out by burning fuel. Heating energy is spent not only on the charge, but also on the boiler.

Electric furnaces have the highest efficiency (50-60%).

These units are:

• arc;
• direct and indirect resistance;
• induction

Electric furnaces have a significant disadvantage; they directly depend on a reliable, cheap source of electricity.

Gas-electric furnaces are a symbiosis of the first two types. Melting is carried out by burning gaseous fuel, and the high temperature is maintained through direct resistance.

Market

The global glass manufacturing market was valued at $127 billion in 2022 and is projected to grow at a rate of 4.1% between 2022 and 2027.

The main factors that can drive the market growth are the ever-increasing demand for consumer electronics and the penetration of artificial intelligence in consumer and business applications.

Flat glass is expected to play a key role in architectural designs over the coming year.

A recent trend sees a rapid transition in building architecture that maximizes natural daylight through the integration of flat glass into roofs and facades. Because triple silver insulated flat low-e glass offers significant energy savings, it can be widely used in green buildings around the world. Solar flat glass is also likely to grow significantly in the next few years.

China is currently the world's leading exporter of glass and glass products, accounting for more than 23% of global glass and glass products exports, valued at approximately $18 billion. Germany and the USA account for approximately 9% and 7% of global glass exports.

Features of melting glass melt at home

You can melt glass at home, but, as in any craft, you need special equipment and compliance with safety precautions. To melt glass, you must strictly maintain the temperature regime and time intervals, since if the time delay is not observed or the temperature increases even by a few degrees, the result can be completely different.

You can use a gas torch to solder the elements. To fully work with glass, you need to purchase a special furnace with a temperature regime of up to 1000 0 C. Glass bottles, perfume bottles, and other glass products commonly used in everyday life are suitable for creating new products. For a high-quality result, it is necessary to thoroughly clean the material from labels and other foreign elements. Melting glass with paint is allowed, but it should be taken into account that this paint will affect the final result.

At home, the fusing technique is most often used. This look does not require a clear outline, but rather helps create a watercolor result. The technique is suitable for making jewelry and other small creative items.

Melting glass at home is associated with a number of difficulties, including calculating the melting temperature of different materials and accurately maintaining a given mode and time.

Sources:

• https://labor-snol.ru/news/kak-rasplavit-steklo
• https://promplace.ru/steklo-staty/-1990.htm
• https://oknaforlife.ru/poleznaya-informatsiya/temperatura-plavleniya-okonnogo-stekla
• https://www.syl.ru/article/319546/temperatura-plavleniya-stekla-maksimalnyie-i-minimalnyie-pokazateli