Question on 'master' molding

[Guest]

Hi all

I've plans to create a silicon mold to make multiple resin castings; the finished item would be a hexagon with 6" sides no more then 1cm deep (intended use for the bases of small dioramas with fibre optics).

BUT ive never done this before and wanted to know if molding in silicon, and not using a great deal of detail, what material would be best suited to make my master 'model' out of? or does it not really matter, can it be a mixture of different non-absorbant materials?

Thanks all in advance

[Ian M]

You can build the master model out of absolutely anything you can find. As long as it is sealed with a non-porous type finish. Gloss paint or varnish for example.

Then it will need a release coat so it will let go of the silicon. Any form of silicon free will do fine. I have read that vegetable oil is good; thin cheap and don't smell!!

Ian M

[Guest]

veggie oil?! lol perfect! that whole response is what i was looking for, thank you

I'll mostly be using randoms bits of kits and plastics 'sheets' so fingers crossed; i'll post a picture on thie thread in a few days and let you know how my first one goes

[Ian M]

Before you cast the resin, dust the mould with talcum powder then give it a blow to get any excess out of the details-

Ian M

[Guest]

Make it out of 30thou (at least) plasticard, with a roof of the same thickness, which will ensure it won't distort, and fix it with good double-sided tape (preferably carpet-fitter's quality) to a 40thou (at least) base. Surround it with walls, at least .25" away, of Lego, also fixed to the baseboard with double-sided tape. With plastic card, and Lego, you won't need a release agent with most silicone rubbers, but do ensure that the top is covered by around .5" of rubber. When the rubber has set, tear the walls away, then peel the whole block of rubber plus master off the base, and push the master out of the rubber block with your thumbs.

Edgar