Why does the varnish layer after painting turn yellow?

Why does the varnish layer after painting turn yellow?

Although the freshly sprayed varnish is unmistakably glossy and smooth, why did it quickly become yellow?

If it was recently painted, it may be because of:

The machinery used to spray automotive paint is not cleaned;

use of varnishes with low varnish clarity that have been damaged or expired;

Incorrect mixing ratio or too inadequate a hardener grade when combined.

Therefore, it is essential to make sure that all painting equipment has been cleaned before spraying car refinish varnish and hardener. After that, spray in accordance with the manufacturer's technical data sheet. Cans of hardener must have their lids securely closed after use to stop moisture from causing damage. The curing agent/hardener should be used as soon as feasible after opening. The varnish coat has to be sanded and re-sprayed if it has become yellow.