Thursday, 6 May 2010

Moulding paste/putties

For some considerable time I have been using Gedeo's Siligum (see below) to reproduce parts in resin, for more information check out earlier posts. Siligum is a two part putty or paste that when mixed produces a soft plasticine type material that will set in about 5 minutes, producing some very detailed and flexible moulds, in to which I usually cast copies in resin. The Siligum is easy to use and produces very fine detail, the set material is extremely flexible and can be twisted and folded to remove quite intricate castings. I would have no hesitation in recommending it, however there is one drawback! It is very expensive, the small pack shown below is now on sale for £9.99 from Hobbycraft and The Range.

In an attempt to cut costs (I use the Siligum quite a bit, mainly to reproduce small repetitive castings or details like these roof tiles or the window castings seen above), I purchased this alternative two part casting putty from e-bay for £19.50. The putty works in the same way - you mix equal parts of both putties and have a working time of about 5 minutes. The big difference between the two products is that while the Siligum is flexible, the Hard Rubber Putty is (as it says on the tin) hard! Very inflexible and even 'biscuity or crumbly'. There is no way that you can 'flex' this set material - it would just crack. The hard rubber putty is available from Restoration Supplies.

There may be the possibility of mixing both products, to produce a cheaper mould, but also one that does not crumble. However the costs of the raw material make this too expensive to risk loosing a whole mould.

In conclusion, the Siligum, is much easier to use and in the long run more economical as the mould lasts so much longer and without damage. There are other similar products that can be used to make simple 'drop moulds', particularly for resin casting, however these also tend to deteriorate quickly and are not suitable for multiple casts.

I would hope that followers who are tempted to produce their own moulds find this review of use.



David Drage said...

A technique that we use for short run moulds is to use silicone sealant (you know, the stuff that DIY stores sell to go around your bath etc.).

Get a bucket of water, squirt the sealant from the tube into the bucket, then remove it by hand (wear gloves), and mould it over your master/plug.

Leave to dry, possibly up to several days depending how think the silicone is.

Works a treat and gives you a nice flexible mould that is great for casting resin in. It is also very cheap as the tubes of silicone can be had for silly prices compared to proper mould making materials.

Theo only two real downsides to this are the drying time, and the vinegar smell from the silicone while setting!

Tony said...

Hi David,

Thanks for the tip. I have some silicone bathroom sealer somewhere in the garage and I'll try it this the next time I need a simple mould.

I have also used Playdough, but the mould is destroyed when the resin is removed.