Also known as: Sandscratch swelling, tramlining, lining up, flatting marks, 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.
Origin and Potential Causes:
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Improper surface cleaning or preparation. Use of too coarse sandpaper or omitting a sealer in panel repairs greatly exaggerates swelling caused by thinner penetration.
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Improper thinner or reducer, especially a slow-dry thinner or reducer when sealer has been omitted.
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Under-reduced or wrong thinner (too fast) used in primer-surfacer causes "bridging" of scratches.
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Primer not well dried before application of color.
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Application of undercoat too heavy.
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Application of color when the original finish is too sensitive to paint solvents used.
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