How Much Fish-Eye Preventer to Use

Advice on measuring and adding the optimum amount of additive to prevent fish-eye. December 28, 2006

Our shop is refinishing an oak table as a favor for a customer (the favor is actually doing this - they are paying for it, but we almost never refinish stuff because of the very problem I'm having with this one). I got the thing totally stripped, sanded, and stained to match what they already have in the house. Looks good. Other than the fish-eye in the 2K poly (Eurobild). I am adding fish-eye killer, but the problem is the directions only say "one ounce per five gallons".

That is shear stupidity. I don't know anyone that refinishes furniture (the main people that use fish-eye killer) that catalyzes five gallons of anything. So, in my quart-cup HVLP gun, how much fish eye killer should I be putting in the quart of spray? Can this be overdosed? It comes with a small squirt tube like sometimes comes with little iodine or medication bottles.

Forum Responses
(Finishing Forum)
From contributor W:
How do you know that you will have a fish eye problem? Why add the stuff if you don't need it? You will be adding silicone into your spray system that may mess up other new work if you do. But if you must, I wouldn't add more than one squirt per quart cup.

From contributor M:
I think I would start with 3-4 drops from an eyedropper in the quart cup. If no fisheyes appear, I would stay with the 3-4 drops per quart until you complete the work. If fisheyes should appear, then double the amount of drops until the fisheyes are flowing out, and are not seen in the coating.

From the original questioner:
The golden rule for refinishing anything you don't know the history of is to use fish-eye killer because of the proliferation of furniture polishes that are full of silicone. I have literally removed 1/8th inch of wood from the surface of wooden tables and the product still fisheyed on me. This table is no exception. I need the fish eye killer because I got fish eyes, and lots of them.

Contributor M, thanks for the advice. I've had to use more than 3-4 drops so far. Can this stuff be overdosed (is two squirts too much in a quart?). You would think an intelligent company like MLC would put better instructions on their product.

From contributor M:
Yes, too much fisheye flow out will cause a cloudy bluish cast in the coating (once that happens, it will not come out). Increase the amount of fisheye flow out into your next coat, and once the fisheyes cease to come out, I would quit while you are ahead of the game.

From the original questioner:
Thanks a lot. I am filling the grain on this oak table surface (which is a good opportunity, anyhow, to sand out the fish eyes that already happened due to insufficient killer). That means probably 4-8 coats total of the 2K poly with heavy sanding in between. Are you suggesting that once I get a good coat lay down that I not need to add any fish-eye killer to subsequent coats?

From contributor M:
No! I meant that, once the coating flows out without any more fisheyes showing, try to quit then, even with a coating or two less. The fisheye killer must be in every coat you apply. Try to stop spraying as soon as possible, so you don't get the blue haze in the coating from too much silicone.

From contributor C:
After the stain is on the tabletop and you are happy with the color, why not use a good vinyl sealer? A light sand is next and then another coat of vinyl sealer. If this dries evenly, put your topcoats on this base coat. Vinyl sealer is a good universal insulator for anything underneath and it dries in about 20 min.

From contributor J:
Another way to add the fish eye eliminator is with a syringe. There are 30 cc/ml to a fluid ounce. There are 20 quarts to a five gallon pail. I would say 1cc/ml per quart would be sufficient. If not, you can add another .5 until you figure out the right amount. It may be hard to determine in the first coat of sealer if they are gone, as those pesky guys have a way of hiding until the second coat.

From the original questioner:
I don't believe 2K poly is compatible with vinyl sealer, though I'm willing to concede if I'm wrong. I'm also not so sure vinyl sealer will seal out the silicone. So far 5 coats of 2K poly - cured over the weekend - haven't.

Contributor J, thanks for the tip. I actually do have a syringe. I always pick up a few of the non-needle types from the vet when our cat gets a bug. They work great and tend to be resistant to thinner. Great idea.

From Bob Niemeyer, forum technical advisor:
Do not use vinyl sealer under 2k urethane ever! Is the fish eye killer you're using from MLC? Is it for 2k urethanes? With fish eye killer or silicone, less is better and the goal is to taper off to almost none. If doing full fill, you should be able to do this. If you are at two squirts and the coat laid down fine, let it dry overnight. Come back next day and sand it to prep for next coat. Shoot a small area with basecoat with no fish eye killer in it. Did it fish eye? PU (urethane) many times will flow over itself and over fish eyes at times. If not, then try just a couple drops at this time to see if it will flow out. Then with next coat, taper off to no additive. Many of these additives will make it fish eye worse if you add too much. Also wash your hands after touching the bottle to help reduce cross contamination. Some of us remember the day when we didn't have silicone additives to fight the fish eye woes, and had to dry fog coats on to get them to lay down. Thank you S.E. Johnson wax and Pledge for all your silicone polish!

From the original questioner:
Bob, your post is fantastic help - thanks! I did manage to get it all worked out, and the table looks great. I was using MLC's Fish Eye Killer, which is indicated on the 2K poly can (which happens to be the same additive recommended for their CV's and lacquers). It worked, along with prayer and fasting.