What's the difference between an ink base and an ink additive?
Base: a finished ink designed to have color concentrates or pigments added. It can be printed and cured by itself without any colors added. Think clear bases, puff base, high density base etc.
Additive: an ink designed to be added to a finished ink to change its properties. In general, additives cannot be printed by itself. It will not cure properly. Think about a puff additive, add 10%-20% to an ink for a puff effect. For a stretch additive, add 25% to improve the elasticity/stretch of a finished ink. As always, there are a couple exceptions to these guidelines, so test before going into production.