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Spraying water based finish

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Forum topic by BalsaWood posted 02-05-2019 09:42 PM 441 views 0 times favorited 6 replies Add to Favorites Watch
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BalsaWood

157 posts in 1665 days


02-05-2019 09:42 PM

I’ve been spraying water based finish and after doing so, the wood \ finish becomes a little rough. I have to lightly sand it down before spraying another coat. Is there something I can do beforehand to prevent this?


6 replies so far

View RobHannon's profile

RobHannon

317 posts in 1037 days


#1 posted 02-05-2019 09:47 PM

Yes, wipe down the piece with damp rag and give it a final sand before spraying the finish. Let it dry and get the sawdust off. Should be good to spray after.

View WoodenDreams's profile

WoodenDreams

736 posts in 417 days


#2 posted 02-06-2019 12:21 AM

this is normal, some wood fibers lift more than others when they get wet. Some will use a damp rag to get the fibers to lift then sand down the fibers. I normally rub on a natural stain, make a couple light passes with sandpaper, then apply several coats of poly, and lightly do a couple light quick passes to remove any lifted fiber if needed between coats.

View Fred Hargis's profile

Fred Hargis

5739 posts in 3000 days


#3 posted 02-06-2019 11:52 AM

I ldon’t worry about it; after the first coat has raised the grain, smooth it out and you’re good to go….no more raised grain.The first coat seals and locks the fibers in place.

-- Our village hasn't lost it's idiot, he was elected to congress.

View F250's profile

F250

32 posts in 260 days


#4 posted 02-06-2019 02:21 PM

Good input above. You can also use a thin shellac seal coat as your first coat, and that will minimize/eliminate grain raising on a lot of woods. Maple and a few others, though, will still raise slightly, but much less than otherwise with the water-based finish as a first coat because the shellac seal coat has a much lower water content in it.

-- Pete -- Bark less, Wag more, and SHOW COMPASSION to everyone you meet.

View ChefHDAN's profile

ChefHDAN

1458 posts in 3356 days


#5 posted 02-06-2019 03:09 PM

If it’s only the first coat, then yes it’s normal from the grain raise. If your following coats are leaving a rough surface, then it can be your gun settings, procedures, and or weather conditions. I spray outside and on a very hot day, I’ve seen the spray almost dry before it hits the surface. In those cases I increase volume to lay a heavier coat, slightly closer to the piece. I’m very much a spray rookie, and have much to learn, but so far with the WB I’ve sprayed, I think I’ve made every goof possible, including getting too much volume and having to flatten an orange peel surface. Practice is the best teacher, have a good sized piece of cardboard to adjust your shots, and keep at it, I’m much happier spraying than dealing with other applications.

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

View LesB's profile

LesB

2201 posts in 3949 days


#6 posted 02-06-2019 05:45 PM

You asked if you can “prevent this”. No not really, it is just the nature of the wood. Some are worse than others.

I always sand lightly between layers of top coats. As indicated in other responses temperature and humidity can have an effect on spraying water based products. I try not to apply a finish if the temperatures are over 75 degrees because it doesn’t have time to level out before it starts to dry and cure leaving an uneven finish.

One advantage of applying a shellac as the first coat is that it drys very quickly so it does not slow down the finishing process. I like to apply a coat of Zinsser’s seal coat that has been diluted about 50% with ethanol or methanol. Zinsser’s is a 2# cut shellac so the dilution cuts it to about 1#. What ever brand of shellac you use make sure it is de-waxed or you top coat may not adhere properly. If it really soaks in quickly you might apply a second coat. This can be done with a brush or just a lint free piece of cloth (wear a neoprene glove to keep you hand clean) If you use a brush clean it with household diluted household ammonia. Under most conditions you can sand it in about 30 minutes and start applying your first top coat.

-- Les B, Oregon

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