Resin is a liquid plastic which can be crystal clear, white, or coloured with pigments. Clear resin is what you will require if you plan on embedding small objects – such as plastic toys, printed paper images or rainbow sprinkles – inside.
The types of resin used in the projects below, and those most used for small scale craft in general, are polyester resins and epoxy resins. They both require two liquids to be mixed together in accurate proportions in order to start off the hardening of the resin.
– Epoxy resins are mainly pouring/coating resins (such as ‘Envirotex Lite’) and are designed to be used in thin layers; to coat images, fill shallow bezels, or fill shallow molds. However, there are also casting epoxy resins, such as ‘EasyCast’ resins, which can be used in deeper molds.
Epoxy resins are more expensive than polyester resins, but they smell much less and are less toxic.
– Polyester resins are used when the molds are deeper than around 0.5″, and with this type of resin, the casts can be poured all in one go rather than in layers. The most common brand of polyester resin is Clear Polyester Casting Resin, which is good to use if you are embedding objects to be displayed within your casting.
A small amount of a ‘catalyst‘ is mixed in with the polyester resin to start off the hardening reaction before the resin is poured into the mold. Make sure you follow the resin instructions and add exactly the right amount of catalyst, as the wrong amount can cause problems later. Mix the components in disposable, unwaxed plastic cups, using wood popsicle/lollipop sticks.
Whilst you’re waiting for resin to harden, cover the open mold with plastic wrap if you like, to stop dust and debris getting inside. Try to keep your workspace clean, to make sure your resin is untainted.
Pouring/coating resins can be poured directly onto a surface to cover it, however most of the time resins will be poured into molds. Molds are basically containers which limit the flow of the resin, and the resin will therefore set in the shape of the mold i.e. if you pour resin in a rectangular mold, you will produce a resin rectangle.
At craft stores you can buy molds specifically made for using with resin, OR you can choose to make your own custom mold in any shape you like. For instance if you wanted to replicate a plastic toy tank in resin then you would use the toy tank to create the mold by building up the mold-making material around it, leaving it to set, and then removing the tank to leave behind a cavity which will be the container for the resin. If you aren’t replicating a pre-existing object, you will have to build the shape from scratch using a solid material such as clay or wood.
More complicated 3D shapes like the tank will require a 2-part mold, where the mold has 2 parts that fit together perfectly before the resin is poured inside, and then when the resin has hardened the mold parts can be pulled apart again to release the resin shape. The molds are reusable.
Only 1-part molds should be used by beginners, so that simple techniques can be practised first before progressing to more advanced designs. 1-part molds are used when the shapes you are making in resin have a flat side (such as jewelry charms) and don’t have too complicated a shape.
A few possible materials you can use to create your own custom mold are:
Silicone rubber (a popular option), re-meltable PVC (Gelflex or Vinamould), or polyurethane resin/rubber. These are all flexible so can accommodate undercuts on the shape you want to cast. Wood and plaster are solid mold materials which can be used – although they must be sealed with primer sealer, and a release agent must be used so the resin doesn’t stick to it.
For coloring resin, opaque and transparent resin pigments are available. It is possible to experiment with different coloring methods such as using oil paints, acrylic paints, fabric dyes, tempura powder, pastels, micro glitter, and even eye shadow, although these could affect curing (solidifying) time. You just have to use trial and error really!
Working with resin: Resin can be drilled and burred. It may be better to use dental burr bits rather than drill bits in order to reduce the risk of chipping. Resin gets hot when drilled so must be cooled regularly.
It’s best to leave resin to cure completely before finishing it by sanding and polishing. A file (e.g. coarse toothed file) is usually used to take off any rough areas and sharp edges. Then wet and dry sandpapers are used with water, starting with coarse grades (p320) and finishing with fine grades (p1200) of paper.
The resin can then be hand or machine polished. Hand polish with liquid metal polish like Brasso, or use a cotton/wool mop on a polishing machine with a specialised polishing compound. A hand-held Dremel could also be used.