Oil and Water based Clays
This page is about Clay, check out the main project index for the rest.
Sculpting in clay and making a mould to cast the finished piece is a the traditional way to make props. This article discusses the difference between Oil and Water based clays, and shows some sample products and projects.
Oil based clay never dries out, this means you can spend many months or longer working on your sculpt. The next part of the process would typically be to make a mould from the sculpt to cast one or more finished items from, so you could also reuse your oil based clay afterwards to make a new sculpt. Oil based clay comes in a variety of firmnesses. A very firm clay often needs to be heated so it is workable, but will hold fine detail very well.
Water based clay is typically firing or air drying so cannot be reused in the same was as oil based clay. However it is generally cheaper in bulk as a result.
Pictured above are some Klean Klay, Some clay from Becks Plastalin, and a lump of WED clay from Laguna clays.
Klean Klay is unfortunately no longer manufactured. At the time of writing there is a small quantity still available in the UK, but it was very popular throughout the US and carries a 60 year legacy. Klean Klay is a medium firmness oil based clay, although it was once available in soft, regular and firm varieties, in a number of colours. Klean Klay is Sulphur free, which is important for Silicone RTV moulding, because some chemicals can otherwise inhibit the cure. Here a sculpt I did in Klean Klay some years ago:
Becks Plastalin are based in Germany, you can obtain this clay on eBay in the UK in a variety of colours as well as the grey ‘Industrial Clay’ which is much firmer. This clay is also Sulphur free.
There are also many other brands of oil based clay such as Chavant, and Roma Plastilina. Some Roma products contain Sulphur, so watch out if you plan to make Silicone moulds.
WED clay is also pictured above. WED stands for ‘Walter E Disney’ as this clay was originally formulated for large prop and scenery sculpts at Disney Land. WED is designed to be slower drying than other water based clays, so it can be used in the same fashion as oil based clays but on a larger scale. WED is not intended to be let to dry or be fired – you are supposed to mould from it when it’s wet, although it’s quite soft so it will need sealing before moulding. Here’s a sculpt I did in WED for my Alien project:
Some clays such as Chavant NSP can be melted to liquid so they can be cast, although this is not the case for any of the clays pictured above.
This means that you could make a life cast of a face in Alginate, make a clay cast so you can resculpt the eyes open and clean up in clay, and then make a final mould from the clay sculpt. If the mould was made of plaster for a latex cast, then the clay could be melted out of the mould.