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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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