A type of glue which comes from many types of tree and plant. It is a by-product of oil; a treacle-like substance that solidifies with the addition of a hardener and an accelerator. Resin is insoluble in water and in art it is used as an ingredient in varnishes. Today, it is one of the new materials used in sculpture, along with silicone rubbers and glass fibres. Resins allow for cold casting, whereas traditional casting methods need heat. In the past soft resins from living trees have been used as well as hard fossil resins such as amber. Clear resin can have objects embedded in it and can be painted.