Fish-Eye Eliminator

I'm going to try spraying some of your Hydrocote Resisthane for the first time. I see that you sell "Fish Eye Stop & Flow Ayd" —does this mean Resisthane fish-eyes easily? Should I use the eliminator routinely?

Fish-eyes, nasty little pea-sized craters in a finish film, occur when the wet finish's surface tension keeps it from flowing over slippery contaminants on the work. Silicone oil is by far the most effective and most common culprit in fish-eye formation when finishing wood. Sources of silicone contamination include overspray from lubricant used in the shop (solution: use spray silicone as carefully as if it were a hazardous material), and silicone oil in popular furniture polishes such as Pledge (solution: charge enough for refinishing jobs to cover the aggravation).

It's important to note that fish-eye is not a common problem for most finishers. Nor are water-based finishes such as Resisthane notably more susceptible to fish-eye than other finishes. Fish-eye earns its bogyman reputation because it's such a pain in the neck to get rid of when it does happen.

The best way to eliminate fish-eye finish is to wash all contaminants off the wood. Generous amounts of mineral spirits or naptha and plenty of elbow grease are the standard prescription. If you can spray flammable material safely, it might work to lay down a thin barrier coat of wax-free shellac, which exhibits lower surface tension than many other finishes.

Fish-eye eliminator, ironically enough, is silicone oil in a vehicle compatible with your finish. By pre-contaminating the finish, it lowers surface tension and lets the finish flow over contaminants on the wood without fleeing and cratering. The downside is that when you use the eliminator, you promptly contaminate your spray equipment with silicone oil. This, of course, sets you up to create fish-eyes the next time you spray, unless you've washed your cup and gun very thoroughly with lots of solvent. Because of this, some finishers opt to use fish-eye eliminator every time they spray, though there may be some cost in terms of adhesion between coats, poor resistance to sags and runs, and reduced final film hardness.

That's why we suggest you use the eliminator only as a last resort. If you must use it, clean your equipment immediately upon completion of the job, and test on scrap to be positive you're silicone-free before tackling the next finishing project.