As the name implies, additives are diverse chemical substances you add to a base of paraffin in order to attain a specific effect or result.
This article introduces you to the available wax additives, their effect (and, sometimes, their side effects) and the situations in which you will use them.
Candlemaking additives serve multiple purposes:
Microcrystalline waxes aren't normally used as a wax base but rather as additives to a paraffin base.
Paraffin (mineral) oil is a popular additive to paraffin when trying to achieve the snowflake effect.
Another additive you may consider using in your candles is the UV-inhibitor. It prevents (or at the very least delays) the premature fading of your colored candles due to the exposition to ultraviolet (or UV) light. When making white candles, add some to prevent the wax from turning yellowish after a long exposition to light.
If you live outside of the United States and don't have access to the extensive selection of wax blends our American friends enjoy, be prepared to make extensive use of different additives to compensate the lack of choice. Sometimes, the mention of some ingredients will sound very weird and you might wonder if, by any chance, I've got some bats in my belfry...
For instance, to achieve a low-shrinkage wax blend for container candles when none is commercially available, you might find yourself using:
If you call the US your home, you can purchase what is called a universal additive. Its composition is a trade secret but it's supposed to contain all the additives you need to achieve great candles. A version specially formulated for soywax is available too. Outside the US, it's notoriously hard to find but don't despair, you don't really need it, the additives available to you will do the job, even if you'll need to do more testing to achieve your perfect candle.