» Improper surface cleaning or
preparation. Use of too coarse
sandpaper or omitting a sealer in panel repairs greatly exaggerates swelling caused by thinner penetration
» Improper thinner or reducer, especially a slow-dry thinner or reducer when sealer has been omitted

» Under-reduced or wrong thinner (too fast) used in primer-surfacer causes“bridging” of scratches
» Primer not well dried before application of color
» Application of undercoat too heavy
» Application of color when the original finish is too sensitive to paint solvents use

» Use appropriate grits of sanding material for the topcoats you are using
» Avoid sanding through to soft or sensitive substrates
» Seal to eliminate sandscratch swelling.Select thinner or reducer suitable for existing shop conditions
» Use proper thinner and reducer for primer-surfacer
» Do not apply coats of primer too heavily
» Use compatible paint systems.

» Thoroughly dry affected area
» Sand smooth, isolate with appropriate sealer, and refinish