Definition- A small, relatively uniform formation of circular craters that may expose the surface of the wood being finished. The depressions are noticeable during drying, and will become less noticeable after complete cure, although they may still be very noticeable.
Causes of Craters/Fisheyes- Contamination on substrate or in coating caused by oils, grease, silicone materials, polishes, cleaners, etc…
- Telegraphing caused by sanding bubbles/blisters in the previous coat.
- Improper mixing of the coating which does not allow the additive to incorporate into the product.
Prevention of Craters/Fisheyes- Avoid use of silicone sprays during wood prep stages (cutting/sanding/milling).
- Keep working environment clean and clear of product which may contaminate.
- Keep all equipment clean and in good condition.
- After repairs/maintenance of equipment, clean excess oils, grease, or lubricants.
- Use caution with refinish projects. Residual material may be left from polishes or cleaners. These may contaminate even after stripping or sanding.
- Adequate sanding when bubbles/blisters are seen.
- Adequate mixing and agitation before and during the application process and necessary.
Possible Fixes for Craters/Fisheyes- Strip and refinish
- Sand and recoat
- For material that has a crater/fisheye problem, an additive may be used in the product. Caution: Most crater/fisheye eliminators are pure silicone. Too much may cause fisheyes, and these products can be a source of contamination.
Questions to Ask- Has the product been altered in any way?
Thinners, retarders, colorants, additives, any other additional adds to the product? - Were there any products (water based, oil based, glazes, stains)used that may have left residual material behind?
- What are the environmental conditions, both during application and cure?
- Have things changed, including equipment and personnel?
- Are the products being used compatible?
- Are the products being used from the same manufacturer?
- Was there any preliminary testing of this system before it was used on a larger scale?
- When in the finish process did you notice the problem?
- Has this problem happened before?
If so, what were the conditions at that time, especially compared to the current conditions? - Has equipment been through any repairs or maintenance recently?
- Are there any other possible contaminations, including lubricants, hand lotions, pretreated wiping rags, etc?
- If this is a recoat job, were any polishes, wax, or other treatments used prior to refinishing?
- If so, was the piece sanded before being recoated?
- Was the product adequately mixed before and during use?
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