RTV Silicone Rubber Block Mould

RTV Silicone Rubber Block Mould

RTV Single Piece Block MouldSilicone will produce a much higher gloss finish than latex, reproduce extremely fine detail, cure in a specified chemical manner but will create issues with regards to the shape of the piece.

Where a latex mould will often demould with fairly severe undercuts a silicone is liable to tear if pushed beyond its elongation boundaries. However that said it will continue its use far past that of a latex mould with superior durability.

A very simple process of mixing is employed with all RTV Silicones be they Addition or Condensation Cure. With our Condensation or "Tin Cure" RTV's the addition rate is usually 20 parts catalyst to 100 parts base silicone. With all our kits they are supplied at the correct ratio for use in one single mix. But if you use a part kit take note of the addition ratios on the labels!!

Addition Cure or "Platinum Cure" RTV's are two part systems, often 1:1 by weight and cured by a different chemical process. They are easily "poisoned" by outside chemicals and naturally occurring items such as onion and garlic. Use caution and very clean mixing kit. Never use the same kit for mixing Addition Cure as you do Condensation Cure.

From the pictures here it's a fairly simple process. Bed the flat side of the piece down in plaster or clay or similar. Build a fence around the object above the highest point by at least 10-15mm.

Mix the silicone and allow to stand for a few minutes to allow primary air release. Then tip SLOWLY into the lowest corner and allow the silicone to rise up and over the former as depicted. If there is very fine detail and you have no de-gassing equipment then paint on a thin layer of silicone first and manually burst any bubbles.

Once the mould is full allow the demould time to pass (at the specified temperature-extend it in colder climates) then remove the fences carefully.

Gently separate the piece from the former and then allow the full cure time to pass. Refer at all times to the Tech sheet that came with the product, either in PDF format or hard copy. This can be accelerated by heating but this will cause shrink of the silicone! Only heat it if you are desperate to start casting, otherwise be patient!

Once all the steps are complete and the correct time has passed (95% full cure is the absolute minimum) you can start casting! Silicone is very forgiving and doesn't generally need release agents unless using a media which will stick to silicone for example Silicone!