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About Casting Resins
There are many different types of casting resins, each with its own benefits and drawbacks. The most common casting resins include acrylics, polyesters, epoxies, and urethanes and polyurethanes. Understanding other types of casting resins helps you determine the best polyurethane resin for you. Acrylic is a very toxic casting resin, typically used in professional casting settings. The beneficial properties of polyester resin make it one of the most common casting option, as it allows a large amount of control during the casting process. Epoxies have similar properties to polyesters, though they are more durable and can withstand higher temperatures.
About Polyurethane Resins
Urethane and polyurethane belong to the elastomer family of casting resins. They have several uniquely specific properties. Most polyurethanes are used as a foam and can be cast in as few as five minutes. Once cast, depending on the make-up and mixture used, can be made rigid or flexible. More affordable polyurethane resins, not tinted during casting, typically result in being yellowish. Many companies offer a slightly more expensive white alternative. Polyurethane resin casts also do not require a sealant when completed to prevent them from moisture damage.
Considerations
When choosing the polyurethane casting resin that's best for you, know that different polyurethane resins have different mix rations. If you are casting several projects at once, you want a polyurethane resin that has a low mix ratio to get the most resin per mix. The time to cast polyurethane also varies by product. For instance; Mold-Quik is a brand of polyurethane resin that can cure at room temperature in 16 to 24 hours.
Drawbacks
The primary drawback of using polyurethane casting resins is the strong odor produced during curing and molding. In fact; many professional and hobbyist casters find that final casts made of polyurethane resin have smells that linger long after curing. The Vagabond Corporation produces an odorless, white casting resin that provides you with the benefits of polyurethane casting without the odor. Additionally, MastCast, produced by Kindt-Collins is another type of casting resin that does not have an odor and creates a pure white cast. White polyurethane casting resins can also yellow over time, particularly when placed in direct sunlight.