Casting resin is a resinous material used in casting. Synthetic resins are often used to make casting resin, although it is also possible to use natural resins. A wide variety of industries use resin in casting, and it is also popular with some hobbyists and craftspeople. For example, resin can be used to create casts for a model railroad, or to create thematic elements used in jewelery making. Suppliers of casting resin include companies which sell wholesale resins to manufacturers, along with craft stores and craft catalogs which sell through mail order.
Resin is a highly viscous fluid which hardens as it cures. In the case of synthetic resins, a catalyst needs to be mixed with the resin so that it will harden properly. Natural resins can be processed in a variety of ways to achieve the desired hardness, and these techniques can include the use of a catalyst. Resins used for casting are often clear, although they can be blended with pigments and dyes to create colored finished products.
To use casting resin, the resin is poured into a mold and allowed to harden before the mold is removed. Rubber and silicone molds are popular because they are easy to use and no mold release needs to be applied before casting. Plaster and other materials can also be used for mold making, and a number of different styles of molds are available.
Many people who work with casting resin make their own molds. Molds can be used to create standardized parts or pieces, ranging from resin beads for necklaces to resin inserts for machinery. After unmolding, a resin object can also be used in turn to create additional molds, as it will be hard and it will retain all of the details of the original mold, as long as the mold was made correctly.
Bubbling, in which small pockets of air are trapped, is probably the most common problem encountered with casting resin. Casting resin also eventually expires, and using old resin may cause problems with casting or setting. For this reason, people usually purchase resin in small batches to meet the needs of a particular project or to accommodate needs within the near future, to avoid having to discard old resin. Resins and catalysts are usually sold separately, and the blending process to add the catalyst can be used as an opportunity to add inclusions ranging from dyes to sparkles.