Sand Scratches

Cause


  •   Sanding the substrate with too coarse grit sandpaper.
  •   Insufficient dry/cure of undercoats before sanding and topcoating.
  •   Refinishing over soft, soluble substrates (e.g., lacquers, uncured OEM).
  •   Using a poor grade and/or too fast evaporating thinners/reducers for spray conditions causing:

      Primer surfacer to "bridge" over sand scratches;

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

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


Repair


  •   Allow finish to dry/cure, sand smooth, compound or polish to restore gloss.
  •   Or, sand and refinish.

 

Prevention


  •   Sand with recommended grit sandpaper.
  •   Allow undercoats to thoroughly dry/cure before sanding and topcoating.
  •   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.
  •   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.*
  •   Use solvent cleaner designated for either lacquer (soluble) or cured enamel/urethane (insoluble) substrates.

*For best results, use the premium two component undercoat system.