SRS 'Silk' Investment Powder
Top quality powder especially suited to palladium white and 18k & 22k gold. For gold casting nothing surpasses the quality of SRS Silk. .
This is our flagship product which is composed of the highest quality and concentration of unmineralised cristobalite
SILK™ offers the following benefits to the Jewellery caster:
High purity raw materials graded and selected especially for jewellery lost wax casting.
Increased refractoriness gives better thermal shock resistance during burnout and casting.
More user friendly able to perform in a wider set of parameters.
Suitable for all metals especially 18kt Gold or fine filigree work.
Smoother surface finish - less polishing required.
Includes all wetting & defoaming agents - no need to add before mixing.
Smooth creamy consistency during mixing and pouring.
SILK™ is easy to break out after casting.
SACK : 22.7 kg. (50 lb.)
Powder / Water Ratio : 100/38-40
Working Time @ 22c Slurry Temp :8 min.
Gloss Off Time @ 22c Slurry Temp : 12 - 14 min.
Thermal Expansion At 750c : 1.1%
Powder can be both dry and steam dewaxed with excellent result. As a general rule the larger the flask the longer the dewax time. Dry dewax in a furnace should take place at about 230c. For a 6″x4″ jewellery mold, 3 hours will be sufficient to remove the bulk of the wax and 2 hours should be sufficient for steam dewax.
Burnout cycles will depend very much on the size of the flask. The larger the flask or the waxes therein the longer and more gradual the burnout must be. For 6”x4” mould will only need 12 hours. In addition the furnace must have a good supply of air in order to achieve a clean burnout. Carbon deposits from the wax must combine with oxygen to form CO2 and thus excape through the pores of the investment. If after Burnout your mould is a gray colour you need to get more air into the furnace-do not increase the temperature, this will only damage the investment.
After completion of burnout, the flask should be cooled to proper casting temperature. The flask can then be cast by either centrifugal or vacuum casting methods.
Temperature of the last 1-2 hours of burnout must be adjusted at correct temperature for casting. If held for less than 1 hour, the core of the flasks will be at a much higher temperature, and may result in metal mold reaction.
The casting temperature varies considerable depending on the size of wax piece and type of metal to be cast. Please contact us for our recommendations.
You can invest with slightly warmer water, the warmer the slurry is when investing the quicker the set time will be. We advise only a few degrees warmer than what you regularly use, as it may set too quick.