The reason PMC shrinks
As explained for the sintering mechanism, silver particles were originally separate. As the sintering process proceeds, they bind with each other. The broader areas then come into contact with each other (growth of a particle) and the gaps grow smaller. Before sintering, there was binder between the silver particles and the apparent gaps were wider. As the sintering process proceeds, the gaps gradually disappear. This is shrinkage. Elimination of gaps means elimination of disadvantages. The fired piece is approaching the density of cast silver. Therefore, such properties as strength and luster can be expected.
Firing conditions of PMC
The table shown below indicates shrinkage (linear shrinkage = longitudinal shrinkage) against firing temperature and time. Shrinkage of each PMC (matrix by temperature and time)
(Total shrinkage from clay to fired piece)
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
Shrinkage
Less than 10%
10% or more and less than 15%
15% or more and less than 20%
20% or more
Generally, it is known that the higher the firing temperature and the longer the firing time, the greater the shrinkage if the starting material is a particle. PMC displays the same tendency. PMC3 shrinks enough at lower temperature, or in a short period of time if the temperature is high. It means the material has excellent sintering properties.
Usefulness of shrinkage (Is shrinkage a problem?)
Because the material in PMC is particles, shrinkage during firing is unavoidable. Using PMC3 as an example, the fired piece needs shrink by approximately 18% in the longitudinal direction compared with the clay piece before firing to achieve the theoretical density of silver (10.5 g/cm3).* As long as it is made of particles, gaps will remain inside even after firing, and the actual shrinkage will tend to be smaller than the theoretical one. If you know how much the shrinkage will be, you can make up for it when modeling. Therefore, no serious problem occurs. Rather, if the shrinkage process stops in the middle, a number of pores remain (like a pumice stone), which creates problems in terms of intensity for accessories. The PMC series uses pure silver particles produced from cutting-edge powder technology in the electronics field. The shrinkage during firing is almost equivalent to the theoretical value. It is the ideal material for creating accessories that people wear. * Reference information: From the dried status, shrinkage by approximately 16% in its longitudinal direction will achieve the theoretical density.
