Casting clear resin involves pouring liquid resin into a mould. The resin hardens and takes on the shape of the mould. There are various types of clear resin, including epoxy resins and polyester resins. Be careful when selecting a resin as some are not intended for casting. Some retain a tacky surface even when cured, and some are very hard to sand or polish. Resins give off fumes when liquid, so ventilation is important.
Casting with Inclusions
Inclusions are items added to the liquid resin which will be left trapped in the piece when it hardens. Common inclusions are photos, coins, beads, sequins, crystals, buttons, fibres and fabric scraps. Some use liquid resin casting as a way to preserve specimens such as plants or insects. You can make steampunk-style or found-object jewellery using inclusions. You may need to build up the resin in layers if you're creating a larger piece, or if you want your inclusions to appear to float at different depths in the resin. If you're tinting the resin, remember that the colour of the resin will affect the apparent colours of the inclusions. Some resins get hot as they cure, and this may damage some items.
Casting in Plastic
Plastic moulds have the advantage of being readily available, inexpensive and reusable. You can often find them in the same stores that supply resin for casting. You can also improvise moulds from plastic items, or make your own plastic moulds using vacuum moulding equipment. Be careful when using improvised or home-made moulds that the plastic is compatible with your resin. Liquid resin can attack some plastic, potentially ruining your project. Test a small amount of resin on the plastic you want to use first.
Casting in Jewelery Blanks
If you are using your clear resin to make jewellery, you can cast directly into jewellery blanks such as pendant backs or ring blanks. Remember that if the blank has an open back, you will have to cover it so the resin does not leak out. You pour the liquid resin carefully into the jewellery blank, along with any inclusions you wish to add.
Doming resin is commonly used for this kind of project. This is a slightly viscous resin that naturally forms a bulge over the base it is poured onto. Doming resin magnifies the items underneath it. (See References 1, 2 & 5)
Casting in Silicone
Resin can be cast in silicone rubber moulds. You cover the original in the liquid silicone moulding material. When the curing process is finished, you will be left with a soft, flexible rubber mould, into which you can pour the liquid resin. This is a very useful technique if you want to make a number of copies of something because the mould can be reused.
Useful equipment for silicone moulding includes a de-gasser, which removes the bubbles from the silicone. Silicone mould release helps you to remove your item from the silicone mould once the resin is cured. (See References 1 & 4)