One of the most basic materials to practice cast sculpture with is resin. Traditionally used for art crafts and decor, resin functions as a hard fundamental casting medium for you to try out casting for the first time. The resin used here is usually a synthetic monomer and not a natural resin. This type of material is commonly used to make polymer plastics. The types of Resins are Epoxy Resin (lower viscosity), Polyurethane Resin, Polyester Resin (shrinks while curing), and Acrylic Resin (good with transparency). An exothermic reaction is caused by mixing polyurethane for example, with a curing agent. This creates heat and causes the combined materials to harden/solidify.
Picture taken by Alessio from Brescia, Italy
Moulds for casting can be made out of several materials, but the two most common ones are silicone rubber and plain plaster. Both can be obtained for a relatively low cost.
Gravity casting is a term used when referring to allowing resin to flow into the mould cavities merely by using gravity's pull on it after letting it pour vertically into a mould. Air bubbles are usually formed when this happens, so a vacuum chamber is always necessary for clean material output. To push the resin material further into the mould (for detailed pieces), sometimes a centrifugal force or pressurized force can be used. There are lots of machines that can aid in the casting process' artistic quality and finesse.
There is another technique called injection moulding, however this involves the creation of a metal mould with a much higher cost rate. The upside is that much more quantity can be produced using a single mould.
Casting art, sculpture or decor with resin is one of the most common commercial and artistic processes anywhere in the world. This technique has even found its way into doll-making, dentistry and toy-making. The possibilities are simply endless.
Beautiful Los Angeles sculpture.