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Origin and Potential Causes:
· 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 used.
Prevention Techniques:
· Use appropriate grits of sanding material for the topcoats you are using. · Avoid sanding through to soft or sensitive substrates. · Seal to eliminate sand scratch 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.
Remedy: · Thoroughly dry affected area. · Sand smooth, isolate with appropriate sealer, and refinish.
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