Edge Mapping,Solvent Penetration
Also known as: Sandscratch swelling, tramlining, lining up, flattingmarks,sanding marks, scratch swelling
Description: Enlarged sandscratches caused by swelling action of topcoat solvents, appearing at the area of the repair where it was sanded through to the substrate.
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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 use -
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 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. -
REMEDY
» Thoroughly dry affected area
» Sand smooth, isolate with appropriate sealer, and refinish