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RTV Silicone Rubber Block Mould - Slit or Knived

RTV Silicone Rubber Slit / Knived Block Mould

A slit or knifed mould is essentially a single piece block mould that had some undercuts that will prevent demould. To facilitate extraction of the cast piece (and its former!), the mould can be sliced open down to the former when initially demoulding. Care should be taken as its easy to slip and cut yourself pretty badly! Two people can do this job much easier than one.

Do not slice a straight line down the block, vary its direction in a wavy or jagged line, as this will help the two halves mate better and reduce any flashing.

We have embedded a you tube video for this process as its easier to watch than describe this! This is also another refresher on making a basic block mould from rtv silicone rubber!