SAND SCRATCHES

(Swelling, Sinking, Shrinkage)

Visible lines or marks in the paint film that follow the direction of the sanding process.

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CAUSE

(A) Sanding the substrate with too coarse grit sandpaper.

(B) Insufficient dry/cure of undercoats before sanding and topcoating.

(C) Refinishing over soft, soluble substrates (e.g., lacquers, uncured OEM).

(D) Using a poor grade and/or too fast evaporating thinners/reducers for spray conditions causing:

(1) Primer surfacer to "bridge" over sand scratches;

(2) Topcoat to "skin over," trapping solvent which swells sensitive substrates.

(E) Using a solvent cleaner that is too strong for the substrate or using thinner/reducer as a surface cleaner after sanding.



REPAIR

(1) Allow finish to dry/cure, sand smooth, compound or polish to restore gloss.

(2) Or, sand and refinish.



PREVENTION

(A) Sand with recommended grit sandpaper.

(B) Allow undercoats to thoroughly dry/cure before sanding and topcoating.

(C) Rub a small area of the old finish with a shop towel saturated with lacquer thinner. If the old finish is soluble or undercured, apply appropriate sealer.

(D) Select recommended thinner/reducer based on temperature, humidity, air movement, and size of repair. Avoid "bridging" existing scratches by applying primer surfacer in thin wet coats, allowing adequate flash time between each coat.*

(E) Use solvent cleaner designated for either lacquer (soluble) or cured enamel/urethane (insoluble) substrates.

*For best results, use the premium two component undercoat system. We recommend HP-5310 or Our HP DTA EPOXY