FAQ: GOLDEN Airbrush Acrylics
GOLDEN AIRBRUSH ACRYLICS
Airbrush Medium and Extender:

What's the difference between Airbrush Medium and Airbrush Transparent Extender?
GOLDEN Airbrush Medium is designed to make non-airbrush paints sprayable. It was GOLDEN Artist Colors' first true airbrush product, and was made to be blended (equal parts) with the Fluid Acrylics to create a paint that sprays well, does not easily clog, and produces a hard, even film. GOLDEN Airbrush Transparent Extender was developed shortly after GOLDEN Airbrush Color line was introduced. It has the same properties as the Airbrush Colors. When you blend Transparent Extender with the Airbrush Colors, the only thing you change is the amount of pigment. It also increases the film strength, which aids in masking techniques. You do not want to add Airbrush Medium to the Airbrush Paints, as you will have an overload of retarders, resulting in a slow drying film.