The firing of coloured glaze is a difficult dialectical unity of paying equal attention to theory and experience, coexistence of control and a series of complicated calculations, divergent creative thinking and rigorous technological process, full of exciting expectations for works and confronting all unpredictable changes in the kiln. Due to the expensive raw materials, technical difficulties, low output, uniqueness and uncontrollable reasons, it is impossible to have two identical glass products in the world. Therefore, glass itself has extremely high economic value and collection value.
Due to the particularity of ancient glass materials and the complexity and arduousness of its technology, it still needs dozens of pure manual processes to make an ordinary ancient glass work today.
First of all, what needs to be done is design, drawing creative ideas into graphic design, and then carving a three-dimensional prototype with materials such as soil or wax.
Next, the silica gel mold is made, that is, the surface of the prototype is coated with silica gel layer by layer to make the silica gel mold, and the shape is fixed with gypsum. Due to careful design and manufacture, the prototype is often damaged after taking off the silicone mold. At this time, the epoxy resin is poured into the silica gel mold to become a permanent model, and then the silica gel female die is made. Then, wax slurry is prepared, and the hot-melt wax is poured into the silica gel master mold. After natural cooling, it is taken out of the silica gel gypsum mold with a fixed shape, shaped and trimmed to complete the wax mold making process.
After the wax model is finished, you need to make a plaster female die. Prepare the correct proportion of refractory gypsum, embed it upside down outside the wax mold, and then put it into a dewaxing machine to be dewaxed by steam heating.
After a complicated mold opening process, Liuli is about to enter her nirvana journey of "coming from the fire". According to the shape and design of the work, the glass raw materials are accurately put into the gypsum mold and sintered in the furnace.
We know that, like Jun porcelain firing, a series of physical and chemical changes in the flame are the key to the fantastic effect of glass, but in a kiln with a temperature as high as 800- 1400 degrees, everything is difficult to be manipulated manually.
Therefore, before entering the furnace, it is very important to preset a series of external factors, such as the proportion of raw materials, the size and distribution of lumps, the possible trend of raw pulp and bubbles after melting, the arrangement of different colors and various effects including transparency. Even all predictable and unpredictable factors, such as the position of the mold in the kiln, the heat distribution and air flow pattern in the kiln, must be carefully deduced.
In the sintering process, accurate cooling has a vital impact on the success of a job. In order to make the glass cool evenly inside and outside and avoid cracking caused by uneven stress release, it is necessary to set a cooling curve. Due to the different designs and shapes of the works, they can be released in as few as three to five days and as many as dozens of days.
Perhaps God will always have the highest requirements for art. Until today, even in the hands of the best manufacturers, the yield of some slightly difficult ancient glasses is only about 60%. There are very few works that can satisfy the real artistic vision. What's more cruel is that the molds of ancient glass are completely disposable, that is, one set of molds for one product. Once the kiln fails, all previous efforts will be in vain. However, the expensive crystal materials for making glass are disposable and cannot be fired repeatedly, thus creating the uniqueness of ancient glass.
After the furnace, if you are lucky enough to get a fairly satisfactory semi-finished product, you can enter the process of "launching".
This process is very similar to the cold working process of many jewels. After removing the plaster mold to get the rough embryo of the glazed work, it is necessary to cut and polish its cross section, carefully carve and trim the delicate part of the work to make the surface more uniform and detailed, and then polish and polish it to show the luster and texture of the work. Only in this way can a work be completed.
Perhaps the "water journey" of ancient glass is not worth showing off, but the process is relatively complicated and the precision is higher. In fact, just as people simply think that "water" and "fire" are incompatible with water and fire, they do not realize the charm and strict requirements of real ancient glass.
Ancient glass must undergo a series of tests such as crystallization and stress relief in fire. Success when leaving the kiln does not mean final victory. Sometimes even a little mistake in the process of kiln casting will bring the consequences of scrapping in the following processing. Therefore, in addition to the scrap factors that may be caused by dozens of cold working procedures, the great risk brought by a "fire" is hidden in the whole processing process from beginning to end.
Today's glass production process can be summarized as the following steps:
1. Creative design: express creativity through graphic design drawings.
2. Prototyping: Carve a three-dimensional model according to the drawing.
3. Making a silica gel mold: evenly coating silica gel on the surface of the mold. After the silica gel is solidified into a silica gel mold, gypsum is needed to fix it.
4. Wax pouring: wax slurry is prepared, and the hot-melt wax is poured into a silica gel female die for natural cold cutting.
5. Remove the wax mold: remove the cold-cut wax mold from the silica gel gypsum mold.
6. Trimming the wax pattern: Cold cutting is easy to shrink and deform the wax pattern, and the trace of the mold line left during demoulding can be carefully trimmed and perfected with tools.
7. Gypsum mold making: Prepare a correct proportion of refractory gypsum and pour it into the modified wax mold to form a wax-containing gypsum mold.
8. Steam dewaxing: all the waxy gypsum is put into a dewaxing machine to be heated by steam, and after dewaxing, the refractory gypsum female die is obtained.
9. Selection of raw materials: In order to accurately control the proportion of various colors and the aesthetic feeling of flowing, it is necessary to select glass raw materials with specific colors and sizes according to the modeling design and arrange the distribution position of color blocks.
10. Sintering in the furnace: After cleaning and dedusting the mold, the whole gypsum mold and the prepared glass frit are put into the furnace and slowly heated, so that the hot-melt softened crystalline glass, such as maltose, slowly flows into the gypsum mold for molding.
1 1. gypsum mold: remove the gypsum mold and take out the cold-cut glass blank.
12. Cutting and repairing: cutting and repairing the excess glass at the grouting hole on the glass blank.
13, coarse mold and fine mold: use coarse grinding and fine grinding abrasives to polish the pouring mouth of crystal glass.
14, cold finishing: carefully carved with tools such as diamond pen to make the surface of the work more uniform and detailed.
15, signature packaging: sign and number the work after confirming its integrity.