Firing PMC
Firing is one of the most important processes and has a major impact on the intensity and luster of the finished project. Sintering property of PMC largely depends on the silver content of clay and the size and shape of the silver particles. The PMC series includes three types of product, each of which has a different sintering property, for a different purpose.
When we consider the sintering mechanism of PMC, the highest possible temperature and the longest possible time ensures the highest strength and the best luster. There is a point in time, however, where the result begins to show no improvement. This is the time specified in the firing conditions.
The electron microscopic pictures below explains the results of complete and incomplete firing. If firing is incomplete, you can see each independent silver particle and the pores between them. If firing is complete, particles are bonded together and you will see fewer pores, just a compacted surface.
 |
 |
| Complete firing |
Incomplete firing |
|
 |
Firing tools for PMC
We recommend four firing tools for PMC. The characteristics of each tool are explained below. If you want to use firing tools other than these, pay close attention to the reachable temperature and safety.
| Firing tool |
Characteristics |
Appearance |
| Silver Pot |
A firing tool designed especially for PMC3. The pot is earthenware (like an aromatic oil burner) and 30 g alcohol solid fuel (often used for hotpot cooking) is the heat source. Light the solid fuel. When the fuel is consumed (after 10 to 15 minutes), firing is complete. It is an easy, safe, sure and reasonable method. Even beginners can fire their projects successfully and thus it is recommended. The piece fired must be up to 20 g in weight and 40 mm x 40 mm in size. Because the temperature in the kiln cannot be controlled, the PMC should not be fired with glass or sterling silver. And, because the piece is heated on an open fire, a hollow shape, imprinting technique (the paste is applied to the patterned indented surface like a leaf and the pattern is imprinted to the clay.), and wire or minute parts of pure silver cannot be used. As long as the maximum temperature in the Silver Pot is 700 to 800 degrees Celsius, PMC Standard and PMC+ cannot be fired. |
 |
| Mini Pan |
A firing tool for PMC3 and PMC+. Use on a compact gas stove (2000 kcal to 3500 kcal. The ones without nozzles in the center are recommended). Light the stove to fire the pieces. Cover the pieces with a special mesh to prevent danger and heat. There is no limit to the size and number of pieces that can be fired, as long as they can be placed under the mesh and the weight is 50 g or less. Mini Pan is not suitable for firing tall pieces (maximum height: approx. 3 cm), hollow pieces with cores, or combination work with glass. It is not suitable for firing PMC Standard. |
 |
| Electric kiln |
A usable electric kiln has a maximum temperature of 900 degrees Celsius and can maintain the internal temperature. Any type of PMC can be fired. The kiln is ideal for complicated shapes and combination with different materials can be fired. The kiln has the fewest constraints on the conditions of the pieces to be fired, and it is safe, stable method of firing. |
 |
| gas torch |
Place the pieces on a heatproof board and use the torch (Yoshinaga Technica's GT3000 series recommended) to fire them directly. Because you can handle the torch monitoring the progress of the firing, you can feel handmade satisfaction. As the temperature rises quickly and the flame temperature can be above the fusing point of silver, you must be careful to avoid melting your work. A handheld gas torch that has a wider flame is also commercially available, with which the temperature of the piece can be kept under the fusing point. |
 |
|
|
|
Firing with different materials
If the firing conditions of different materials fall under the ones for each PMC, they can be fired at the same time. Because firing with different materials requires temperature control, an electric kiln is recommended. Typical materials and firing conditions are listed below:
| Materials |
Firing methods and conditions |
| Synthetic jewels |
Cubic zirconia, synthetic ruby, and sapphire can be fired with all types of PMCs. Apply recommended firing conditions of each PMC. |
| Genuine jewels |
Theoretically, ruby and sapphire can be fired with all types of PMCs according to their physical properties. In this case, apply the recommended firing conditions of each PMC. Genuine jewels, however, contain microelements so that they may be discolored during firing. Or, they may crack due to thermal shock. Bear these risks in mind when firing genuine jewels with PMCs. Place such jewels on the pieces after firing whenever possible. |
| Pure silver wires and parts |
They may be fired with all types of PMCs. Apply the recommended firing conditions for each PMC. |
Silver 925
(sterling silver)
and silver 950 |
They may be fired only with PMC3. Fire them at 600 degrees Celsius for 30 minutes. Firing at temperature higher than 600 degrees oxidizes the copper contained in silver 925 and 950, making the fired pieces fragile. |
| Brass and copper |
They may be fired only with PMC3. Fire them at 600 degrees Celsius for 30 minutes. Firing at temperature higher than 600 degrees oxidizes the brass and copper, making the fired pieces brittle. Even firing at 600 degrees oxidizes and blackens the surface. In this case, use sandpaper to polish it. |
| Glass |
If the softening point(*) of the glass is higher than the firing temperature, the shape before firing is maintained. If it is lower, the glass melts and the shape will be rounder due to surface tension. If you want to fire glass with PMC, you need to slow cool them until they reach the strain point.(**) |
| China and porcelain |
Basically, they can be fired with all types of PMCs. Apply the recommended firing conditions for each PMC. Some types of china and porcelain are sensitive to thermal shock. In this case, you need to slow cool them. |
|
* and **: Physical properties of glass. We recommend looking them up before using.
Those material cannot be fired with PMC, it is possible to fire the PMC first and then glue the material onto the fired PMC. The following are the conditions of materials that cannot be fired with PMC.
• Materials that burn when fired with PMC. (e.g.: diamond, wood, and plastic)
• Materials with fusion points lower than the firing point of PMC. (e.g.: wax and solder)
• Materials that deform (e.g.: some types of glass)
• Materials that discolor (e.g.: some types of genuine jewels and glass)
• Materials sensitive to thermal shock (e.g.: some types of genuine jewels)
|
| |
Recommended firing conditions by category
Listed below are the recommended firing conditions by category.
Recommended firing conditions by category (guidelines to obtain appropriate strength)
|
|
Firing temperature (°C) |
|
|
|
600 |
650 |
700 |
750 |
800 |
850 |
900 |
|
| Firing time (minutes) |
5 |
|
|
|
|
|
|
|
PMC3 |
| 10 |
|
|
|
|
|
|
|
| 20 |
|
|
|
|
|
|
|
| 30 |
|
|
|
|
|
|
|
| 60 |
|
|
|
|
|
|
|
| 120 |
|
|
|
|
|
|
|
| 5 |
|
|
|
|
|
|
|
PMC+ |
| 10 |
|
|
|
|
|
|
|
| 20 |
|
|
|
|
|
|
|
| 30 |
|
|
|
|
|
|
|
| 60 |
|
|
|
|
|
|
|
| 120 |
|
|
|
|
|
|
|
| 5 |
|
|
|
|
|
|
|
PMC Standard |
| 10 |
|
|
|
|
|
|
|
| 20 |
|
|
|
|
|
|
|
| 30 |
|
|
|
|
|
|
|
| 60 |
|
|
|
|
|
|
|
| 120 |
|
|
|
|
|
|
|
|
| |
Producible under the condition |
| |
All producible items including bangles, rings and pendants |
| |
Ring and pendant |
| |
Pendant |
| |
Inappropriate condition |
|
To clarify the standard, they are the firing conditions for an electric kiln. For other firing tools, it is difficult to define the conditions because they depend on the environment and the types of pieces to be fired. The conditions shown below are guidelines only.
Silver Pot: 10 minutes at 750 degrees Celsius
Mini Pan: 800 to 850 degrees Celsius |
|
