I currently have a problem with a water based poly from Valspar which I bought in the spring. I know it’s milky colored in the can and I used it on a project this spring and it was fine so I sealed it and put it on the shelf. I recently re-opened it for a project and put it on and when it dried there were these tiny black spots, pin head size, on the finish. I sanded it down and put another coat down. Again the same thing so I tried just picking these small black spots off but they like,burst. Thats right burst which lead to a larger spot and more sanding. I tried a second can and it did the same thing. Black spots which burst when you try to get them off. I e-mailed the the company but I never got an answer. Does anyone know what causes this and whats a good cure?
Dave in Pa.
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Replies
Try on another piece of wood. The dots might be bits from sanding. What are you sanding with?
The first thingI would check is to see if it came in a metal can. Is there rust particles floating around in the finish? Its always a good idea to strain WB poly before you spray.
I saw this many years ago when a client of mine did his own finishing with a water-based finish. He had used steel wool between coats and got the black spots. In your case, I don't know since it was the first coat, but it sounds like a problem with your wood preparation rather than a finish problem. Steel wool cannot be used with water-based finishes. The iron oxide is black, and every little microscopic particle of it will leave a black spot. It is the same thing that ebonizes wood the old fashioned way.
Did you use a sanding sealer which you smoothed with steel wool? Did you vacuum the wood prior to finishing? Do you have a ton of flies there? Okay, just kidding about the flies.
Also, you should always filter your finishes prior to use with a fine paint filter. It makes a big difference in the finished product.
Hal
http://www.rivercitywoodworks.com
No steel wool in the shop for that reason. The topcoat I am covering is ultra white latex paint and I have used this technique several times with Min-wax. Files are kept in a totally different area. Won't oil float on top of the poly? I am not spraying but filtering it sounds like a good idea. A paint associate at Lowes said somebody else used it and used a foam brush. That has to checked out.
Dave in Pa.
Pour some out on a clear plate and take a look. There is something in your paint (obviously!!).
Filter through a coffee filter and see what you get. Actually with bursting when you touch them it sounds like you might have some oil in there.
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