My last project was a simple pair of matching step-up stools for my kids. I learned alot about mortise and tenon and flattening boards by hand, but what stumped me was the finish. I used a water based Polyurethane and it dried so fast that you can see brush strokes in reflective light. I liked using it (and I still have 3/4 can left). Any tips on putting it on and eliminating brush strokes? The only hints I can give are in the conditions. We run a fireplace in the basement and it was warm (hot) and, I assume, very dry. Could this be as simple as using a better brush or do I have to wait for the spring to move back out in to the garage?
Thanks,
Thomas
Replies
All finishes tend to want to be flowed on with minimal back and forth brushing. With waterbornes humidity that is too low is a problem. The water evaporates fast and doesn't give the finish time to properly flow out. I avoid finishing with waterbornes in relative humidity below 40-50%.
You need not live with the brush strokes forever. You can lightly sand them off, (Using 320 grit) and then apply one more coat under conditions of a little better humidity, like Howard suggests. You still need sufficiently warm temperatures to get the necessary coalescence of the finish, but about 70° is fine much higher and you significantly reduce the time for the finish to flow out. Howards point about having relative humidity is particularly important. You can get a humidistate with enough accuracy for these purposes, for very little money, at almost any hardware store.
You didn't mention what kind of brush you used. Good brushes make a difference. Lot's of people like the very fine bristled synthetics similar to those used on shellac, but that's more important for the waterborne finishes that are quite thin, almost better suited for spraying.
Technicque is important. With waterborne it isn't like varnishing where you lay it on, and then spread it out by working with the brush, followed by a "tipping" off with the brush held almost vertically. With the waterborne you need to work quickly and methodically. If you see you have left brush strokes, then tip them off immediately, and go on quickly enough so you are retaining a wet edge, becasue if you wait you will do more harm than good.
I picked a day that was warmer and the humidity was much better. The finish went on great, and I am back to really loving this product. Thanks for the tip on keeping it wet and moving quickly.
Thomas
What is the name of the product?If it's a good product, easy to apply, and you pleased with it, please tell us what it is!
I was away and just saw this. I use waterbased poly a lot. I generally don't us a brush. I use the spongy pads with the hairy outside. More than one coat obviously and sand 220 between coats. First coat I sometimes use cheese cloth instead of the pad.
Then if you really want a good smooth finish after say 3 coats. I rub it out.
ASK
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