Paint Defects 6 – Fish Eyes

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fish_pictoFish eyes are a type of coating defect which is characterized by circular voids or separation in the coating. Fish eyes are small, crater-like openings in the finish after it has been applied. They are usually caused by oil and grease on a coating substrate.

Fish eyes are also known as silicone contamination, poor wetting, saucering, pits, craters and cissing.

Fish eyes are a typical defect when paint is sprayed. They are small quasi-circular areas of substrate that are exposed through the applied coating immediately after application and which have at their center a source of contamination. Fish eyes can be caused by oily spots or silicone particles and/or by airborne droplets that are deposited on the painted surface.

When a coating is applied to a substrate that is contaminated with low surface energy particles such as oil, wax, grease or silicone, fish eyes may develop in the coating as it is applied. These fish eyes are produced because the coating is unable to wet out the contaminated area.

fish eyesFish eye is a preparation defect. If the surface has been properly cleaned and degreased using a wax and grease remover, fish eye can usually be prevented completely. If fish eye does occur, particularly in the first coat, often painters will let that coat fully tack off, then follow it by a second coat, which often “bridges” the fish eye so that it becomes invisible. A third coat is applied, not only for full coverage but also to make sure that there is sufficient paint for detailing later. After the paint is fully cured, if slight remnants of the fish eye are visible, it can be sanded and polished.

If during the second coat the fish eyes are not bridged, it is highly unlikely that a third coat will accomplish an acceptable result. Therefore, in this instance the finish should be dried, sanded and repainted.

CAUSES:

  • Contamination by wax, silicone, oil or grease.
  • Contamination by soap residues, detergents or metal cleaning products.
  • Contamination of the surrounding air (proximity to mechanic shop).
  • Contamination from use of polishes or aerosol spray containing silicone.
  • Contaminated air lines
  • Effects of old finish and previous repair (May contain excessive amounts of silicone)
  • Use of thinner/reducer in place of a solvent cleaner.
  • Spraying over previously repaired areas containing “fisheye eliminator” additive.
  • Improper or insufficient surface cleaning or preparation.

PREVENTIONS:

  • Thoroughly degrease surface with a wax and silicone remover.
  • Regular maintenance of air supply/equipment.
  • Make sure that all products containing silicone are used as far away from the workshop as possible.

SOLUTIONS:

  • Remove wet paint film with solvent, clean and refinish.
  • Add the recommended fisheye eliminator and respray the affected area.
  • If fisheyes appear in a basecoat, allow the color to flash then spray a mist coat over affected area. Do not use fisheye eliminator in undercoats or basecoat color.
  • Thoroughly clean the surface to be painted with detergent and hot water, followed by the recommended solvent cleaner. Wipe dry with clean rags.
  • Install an air filtering system that removes and prevents oil and moisture contamination.
  • Apply mist coat.
  • Sand panel, isolate and repaint.

REFERENCES:

  1. Lusid Technologies, Painting Defects, data of access: 19 July 2016 http://www.lusidtechnologies.com/index.php/paint-defects
  2. TranstarAutobodyTechnologies, Paint Defect/Troubleshooting Guide, data of access: 19 July 2016, https://www.tat-co.com/TranstarAutobodyTechnologies/media/TATCo/Product%20Assets/Flyers/Z632-Paint-Defect-Troubleshooting-Guide.pdf
  3. Sherwin-Williams, Fisheyes, data of access: 19 July 2016, http://www.sherwin-williams.com/homeowners/ask-sherwin-williams/problem-solver/sagging-wrinkling/sw-article-dir-fisheyes.html
  4. CorrosionPedia, Fish Eyes, data of access: 19 July 2016, https://www.corrosionpedia.com/definition/513/fish-eyes
  5. Source Auto Parts, Paint Detailing Techniques: How to Approach Commonly Seen Defects, data of access: 19 July 2016, http://www.searchautoparts.com/abrn/technicians/training/paint-detailing-techniques-how-approach-commonly-seen-defects