Furniture Repair and Assembly/Finish Fisheye
QUESTION: I am refinishing two nightside table tops and finally got the stain to match. I put the first coat of polyurethane on and other than a hair from my brush and a few little imperfections, it looked great. I used steel wool and smoothed down all imperfections and then used tack cloth to clean any particles off. I put the second coat on and after letting it dry for about 6 hours noticed after looking closely that I had several areas with fish eyes. What is the best way to fix this? Do I have to take all the polyurethane off and start all over again or could I use sand paper to hopefully get through to the first coat where I had no fish eye problems? Was the tack cloth the problem? I used an oil based stain, so after sanding could I use mineral spirits diluted to clean the surface rather than a tack cloth? Thank you for any help you can give.
ANSWER: First lets look at what causes "fish eyes". A fish eye occurs when there is some kind of contaminate that brakes the surface tension of a wet finish. In other words, it will not let the finish flow over it. In your case its not the tack cloth its the steel wool that was used between coats, Steel wool has a fine oil on it to prevent rusting. This oil may or may not cause a problem depending on the type of finish used. That's one reason why its best to use steel wool for the final rub-out rather then between coats.
Use "free-cut" sand paper between coats. It is designed not to clog when sanding a finish. Sanding does a much better job or leveling the surface. Steel wool will smooth the surface but will not cut off the high spots or dust bumps, it will round them off instead.
There are products on the market such as "fish eye flow out" and "smoothy" that are added to your finish to help prevent fish eyes and other problems. But they can create other problems sometimes.
To repair fish eyes you will need to sand them out and re-coat with new finish. Be very careful NOT to cut through the finish to the stained wood as this will distort you color. Its better to sand several times, not as hard, and re-coat. Also several thin oats is much better than a very thick coating.
Do not use solvents to clean the surface between coats. Use a high pressure air hose of tack cloth.
---------- FOLLOW-UP ----------
QUESTION: Ok, I followed your directions and I put my final coat of varnish on but it has several bumps in the finish. When I use the steel wool to rub them out you can see that spot is dull. How do I get the imperfections out without messing up the finish?
There is a major difference in appearance between a rubbed out finish and one that is "off the gun" (spray gun) or brushed. Any type of abrasives used to level and smooth a finish will leave serrated marks that defuse the reflected light giving a lower sheen appearance, i.e., hand rubbed look.
As I stated earlier steel wool is not
used for removing dust bumps, sanding with a flat block is used to correct this problem.
The rubbing out process depends on what "the look" is that you are trying to achieve. It is an over all process not for correcting problem spots
. If finish imperfections like brush marks or dust bumps are present then sanding the entire surface area effected with an appropriate grit and type of sand paper is the first step. Then using finer and finer abrasives like pumice and rotten stone, scotch-bright pads, steel wool or compounds are used to achieve the final desired sheen. All sanding and rubbing out is done in one direction with the grain of the wood in most cases.