Definition
An additive mixed into aircraft finishing materials such as paint, dope, or lacquer that slows the rate of evaporation of the solvents, allowing the finish to flow out smoothly and cure properly under conditions that would otherwise cause defects like blushing, orange peel, or premature drying.
Plain English
A liquid you add to paint or dope to make it dry more slowly, so it has time to settle into a smooth, even finish before it sets.
Context Anchor
Seen in aircraft fabric, paint, and coating work, especially when a finish is being mixed or adjusted for temperature and humidity conditions.
Derivation
From the Latin retardare, meaning to slow down or hold back. The name describes exactly what it does: it holds back the drying of the finish.
Why Pilots Care
A properly applied finish helps protect aircraft surfaces. If a finish dries too fast, it can leave defects that may require rework by maintenance personnel.
Grounding Statement
On a hot or humid day, retarder can give a wet coating a little more time to settle before it dries.
Intuition Check
Do not think of a retarder here as a brake for the aircraft. In finishing work, it means an additive that slows the drying of a coating.
Example Sentence 1
On a hot, humid day, the technician added a small amount of retarder to the dope to prevent blushing as it dried.
Example Sentence 2
In warm hangar conditions, a small amount of retarder prevented the paint from drying too fast and causing orange peel.