Troubleshooting guide for dirt in coatings.


Also known as grains, specks, grit, nibs, bits and dirt inclusions. This defect will show particles in the coating. These particles can range from large to small.


  1. Dust/dirt/contamination from sanding, cloths, the applicator, nearby equipment etc.
  2. Dried spray dust accumulation in the booth
  3. Electro-static attraction of dust to the surface. A static charge on a surface attracts dust and small particles. Many of the HMG degreasers are anti-static to aid with this issue.
  4. Use of low quality masking tape.
  5. Tack rag not used immediately before application, (or sometimes at all).
  6. Contaminated/poorly filtered air lines
  7. Paint kept in dirty paint cans
  8. Failure to remove any “skins” that may have formed in synthetic finishes. This is generally only when the can have been opened and closed allowing air to the product.
  9. Paint was not sieved/strained before use
  10. Paint has been kept longer than its shelf life, (see technical data of specific product).
  11. Incorrect thinner or hardener used.
  12. Tinters not adequately stirred/shaken into base
  13. Using re thinned two pack materials after the recommended “pot life”.
  14. Dirt, contaminants, oil and dust blown out of crevices and cracks such as wheel arches, seams, door shuts etc.


  1. Keep the spraying area as clean as possible and free of dirt and rubbish. Clean tyvek suit overalls, (available from HMG) should be worn.
  2. Spray booth filters should be changed regularly.
  3. Blow out seams, cracks, wheel arches etc
  4. Use a tack rag immediately before application
  5. Carefully remove skin that may have formed in previously opened paint.
  6. Make sure equipment such as air lines, spray guns and filters are well maintained and cared for.
  7. Clean the surface before starting the job!
  8. Mix in tinters to base thoroughly before usage.
  9. The material should be strained before use
  10. Do not exceed recommended pot life
  11. Use an anti-static degreaser especially on non-metallic surfaces


Minor cases of dirt can be rectified by a fine compound solution and polishing. For more severe cases sanding and refinishing may be necessary.