Fourth, firing
The heat source for firing is electricity, gas, heavy oil, etc. The most effective one is electric heating, which is used to print high-grade products such as glasses, tableware, and cosmetics bottles. In addition, special prints of gold and platinum are indispensable for electric heating, but its cost is higher than oil and gas.
The cost of heavy oil is lower than that of electricity, and the heat is also high. It is suitable for firing beverage bottles or heavy weight single products. Gas is mainly used for glass products that cannot be used for electric and heavy oil firing. When using a heat source other than electricity, a flame furnace must be used.
The types of firing furnaces, besides the conveyor tunnel type and the trolley tunnel type, are also single chamber types such as square furnaces and round furnaces, each having different characteristics.
Conveyor tunnel type firing furnace has high efficiency, high output, easy adjustment of heat, suitable temperature, and good workability.
Trolley-type tunnel furnaces are mainly used for glassware that are not suitable for conveyor belts and are prone to tripping in the furnace, as well as small, large, flat, high-quality, low-volume glass products such as: Small flat glass products are divided into two layers and three layers on a trolley, which can be fired at a time. It is also possible to burn tall glass products that cannot be put into other furnaces. Although this kind of firing furnace is somewhat inconvenient in operation, it can double the efficiency of firing a large number of small-size glass products compared to conveyor belt tunnel furnaces. In this sense, it is a convenient and widely used firing furnace.
Various single furnaces are mainly used for firing small-diameter items for testing and only one process glass product.
The firing temperature is about 520 to 600°C, and when the organic hydrocarbon compound in the glaze is completely burned out, the glaze starts to develop color, and the glass is melted on the glass surface. At this time, if the heating is rapid, the glass product will crack under the heat shock; if the cooling is too fast, the glass product will also be skewed and broken. Therefore, in the range where the glass product is not broken, the temperature can be gradually increased to reach the maximum temperature in the furnace, and then the temperature is gradually lowered. Since temperatures between 500 and 600°C are the most prone to skew, the speed must be adjusted according to the thickness and weight of the glassware. The time for firing the tunnel should be different depending on the structure of the furnace and the weight of the glassware, but it generally takes about 90 minutes.
The adhesion of gold and white gold is poor, so it is best to control the firing at high temperatures without skewing or cracking, but when firing with other colored glazes, especially in the case of mixed colors, the weaker The glaze is easy to lose color and fade, and the hue tends to change. Therefore, special attention must be paid to temperature control.
When firing a glass product printed with a thermal glaze, gas is generated due to the combustion of the medium and the organic compound, and various adverse effects are generated. Therefore, it is necessary to strengthen the exhaust of the furnace. If fired for a long time, coal gas and soot will stick to the lining, which will have an adverse effect on the firing. Such as continuous firing, the color will change color, loss of luster, gold into black, etc., to overcome is: when placed on the conveyor belt at least 3 meters apart, and the temperature can not be reduced. In addition, when placing products on the conveyor belt, if the gap is not uniform, color differences and other obstacles will occur. Therefore, if possible, the product is ideally placed on a special furnace for heating glazes. The firing is straight.
There are different opinions about the firing temperature. Each furnace should have its own temperature standard. Even if it is a furnace with the same design, due to the difference in the insertion position of the resistance and the length of the protrusions in the furnace, the temperature will differ by about 30-50°C. Due to the difference in design, heat, and speed of the furnace, although the same glass product is fired, the A furnace may be 500°C, and the B furnace may be 600°C. Therefore, it is not important to pay attention to the temperature of others, but to master the temperature standards of the stoves that they use.
Five, glass screen printing matters needing attention
Matters needing attention in glass printing are listed as follows:
1 Wipe the moisture, oil and dirt on the glass surface before printing.
2 Gold and white gold must be pickled before printing on important glass products.
3 When the color of the finished product changes due to hydrogen sulphide, it can be corrected by wiping the cloth with an oxalic acid solution.
4 When the color change is severe, it can be restored by re-burning at a temperature of 480°C or more.
5 During the rainy season (in summer), discoloration is likely to occur, so the material should be kept in a safe place.
6 To prevent lead poisoning, good exhaust equipment must be provided.
7 Smoking and eating are strictly prohibited at work.
8 Wash hands and gargle before meals.
9 Do not touch the glaze directly with your hands.
The new color glaze must undergo a lead poisoning test, and a positive reaction cannot be used.
Six, lead poisoning test
In recent years, the pollution has become more serious day by day. Poisoning by heavy metals such as lead and tin is a very serious problem. Glass Printing In order to prevent public hazards, it is necessary to use colored glaze with less lead as much as possible, and exhaust devices must be installed at the same time.
If the printed glass tableware contains lead, this will not only adversely affect the user, but also affect the reputation of the producer. Therefore, a sufficient lead poisoning test must be performed on the color glaze in advance, and it must be used to achieve the use of indicators.
The fired glass was washed carefully with water and used as a sample. Then 1000 ml of distilled water heated to 50°C was placed in a beaker. The sample was placed in a beaker and kept at a temperature of 50°C without stopping. After stirring for 30 minutes, the sample was taken out, and distilled water was used as a test liquid.
10 ml of the test solution was placed in a test tube, 3 ml of acetic acid and 2 drops of a 5% potassium chromate solution were added and left for 30 minutes. If the liquid shows cloudy yellow or precipitates at this time, it is a positive reaction and it is unqualified.
The heat source for firing is electricity, gas, heavy oil, etc. The most effective one is electric heating, which is used to print high-grade products such as glasses, tableware, and cosmetics bottles. In addition, special prints of gold and platinum are indispensable for electric heating, but its cost is higher than oil and gas.
The cost of heavy oil is lower than that of electricity, and the heat is also high. It is suitable for firing beverage bottles or heavy weight single products. Gas is mainly used for glass products that cannot be used for electric and heavy oil firing. When using a heat source other than electricity, a flame furnace must be used.
The types of firing furnaces, besides the conveyor tunnel type and the trolley tunnel type, are also single chamber types such as square furnaces and round furnaces, each having different characteristics.
Conveyor tunnel type firing furnace has high efficiency, high output, easy adjustment of heat, suitable temperature, and good workability.
Trolley-type tunnel furnaces are mainly used for glassware that are not suitable for conveyor belts and are prone to tripping in the furnace, as well as small, large, flat, high-quality, low-volume glass products such as: Small flat glass products are divided into two layers and three layers on a trolley, which can be fired at a time. It is also possible to burn tall glass products that cannot be put into other furnaces. Although this kind of firing furnace is somewhat inconvenient in operation, it can double the efficiency of firing a large number of small-size glass products compared to conveyor belt tunnel furnaces. In this sense, it is a convenient and widely used firing furnace.
Various single furnaces are mainly used for firing small-diameter items for testing and only one process glass product.
The firing temperature is about 520 to 600°C, and when the organic hydrocarbon compound in the glaze is completely burned out, the glaze starts to develop color, and the glass is melted on the glass surface. At this time, if the heating is rapid, the glass product will crack under the heat shock; if the cooling is too fast, the glass product will also be skewed and broken. Therefore, in the range where the glass product is not broken, the temperature can be gradually increased to reach the maximum temperature in the furnace, and then the temperature is gradually lowered. Since temperatures between 500 and 600°C are the most prone to skew, the speed must be adjusted according to the thickness and weight of the glassware. The time for firing the tunnel should be different depending on the structure of the furnace and the weight of the glassware, but it generally takes about 90 minutes.
The adhesion of gold and white gold is poor, so it is best to control the firing at high temperatures without skewing or cracking, but when firing with other colored glazes, especially in the case of mixed colors, the weaker The glaze is easy to lose color and fade, and the hue tends to change. Therefore, special attention must be paid to temperature control.
When firing a glass product printed with a thermal glaze, gas is generated due to the combustion of the medium and the organic compound, and various adverse effects are generated. Therefore, it is necessary to strengthen the exhaust of the furnace. If fired for a long time, coal gas and soot will stick to the lining, which will have an adverse effect on the firing. Such as continuous firing, the color will change color, loss of luster, gold into black, etc., to overcome is: when placed on the conveyor belt at least 3 meters apart, and the temperature can not be reduced. In addition, when placing products on the conveyor belt, if the gap is not uniform, color differences and other obstacles will occur. Therefore, if possible, the product is ideally placed on a special furnace for heating glazes. The firing is straight.
There are different opinions about the firing temperature. Each furnace should have its own temperature standard. Even if it is a furnace with the same design, due to the difference in the insertion position of the resistance and the length of the protrusions in the furnace, the temperature will differ by about 30-50°C. Due to the difference in design, heat, and speed of the furnace, although the same glass product is fired, the A furnace may be 500°C, and the B furnace may be 600°C. Therefore, it is not important to pay attention to the temperature of others, but to master the temperature standards of the stoves that they use.
Five, glass screen printing matters needing attention
Matters needing attention in glass printing are listed as follows:
1 Wipe the moisture, oil and dirt on the glass surface before printing.
2 Gold and white gold must be pickled before printing on important glass products.
3 When the color of the finished product changes due to hydrogen sulphide, it can be corrected by wiping the cloth with an oxalic acid solution.
4 When the color change is severe, it can be restored by re-burning at a temperature of 480°C or more.
5 During the rainy season (in summer), discoloration is likely to occur, so the material should be kept in a safe place.
6 To prevent lead poisoning, good exhaust equipment must be provided.
7 Smoking and eating are strictly prohibited at work.
8 Wash hands and gargle before meals.
9 Do not touch the glaze directly with your hands.
The new color glaze must undergo a lead poisoning test, and a positive reaction cannot be used.
Six, lead poisoning test
In recent years, the pollution has become more serious day by day. Poisoning by heavy metals such as lead and tin is a very serious problem. Glass Printing In order to prevent public hazards, it is necessary to use colored glaze with less lead as much as possible, and exhaust devices must be installed at the same time.
If the printed glass tableware contains lead, this will not only adversely affect the user, but also affect the reputation of the producer. Therefore, a sufficient lead poisoning test must be performed on the color glaze in advance, and it must be used to achieve the use of indicators.
The fired glass was washed carefully with water and used as a sample. Then 1000 ml of distilled water heated to 50°C was placed in a beaker. The sample was placed in a beaker and kept at a temperature of 50°C without stopping. After stirring for 30 minutes, the sample was taken out, and distilled water was used as a test liquid.
10 ml of the test solution was placed in a test tube, 3 ml of acetic acid and 2 drops of a 5% potassium chromate solution were added and left for 30 minutes. If the liquid shows cloudy yellow or precipitates at this time, it is a positive reaction and it is unqualified.
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