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Brush marks in finished work

J

Jerry Lear

Joined
May 4, 2012
Messages
36
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Location
Baldwin, Maeyland
I just finished a cherry platter, sanded to 420 grit, applied Danish oil & let dry. I then applied three coats of water based poly with a foam brush, letting each coat dry. After totally dry, I sanded from 500 to 6000 grit.
I noticed that there were brush marks in the finished product. I was careful not to go over the same areas.
Is there something I am doing wrong? Is there a way to eliminate or minimize these marks?
Thanks,
 
FWIW, I'm not a fan of foam brushes. I asked a retired commercial/industrial painter about brushes at Lowes. He highly recommended Purdy products. That is what I have for my own use. It's a pain to clean up but I have only used them for latex paint so they are easy to clean. No experience in poly finishes or varnishes. Sorry I can't be of more help.
 
You didn't sand it properly. You should have removed all the brush marks with the 500 before moving to the finer grits. Get a better light to work under. Don't move to a finer grit until you have an even sheen from the previous grit. If you get a lot of marks, sand between coats of poly finish with 320 grit.
 
If you are dry sanding, you can usually see the glossy spots amongst the matte. The glossy would be the areas that are still not level and will show up as brush marks.
There is the possibility that it is sanding marks in the wood itself too.
 
It is also possible that what you see are sanding scratches in the wood. Before any oil or film finish is applied I carefully the wood to make sure that all scratches from the previous grit have been removed.

One description I've heard that makes a lot of sense is that the coarsest grit smooths and levels the surface ... and all subsequent grits are just to remove the scratch marks of the previous grit.
 
In my experience, water base poly is tougher to apply than oil base. However, I still like to use it especially with spalted wood, it preserves the natural wood color compared to the amber tones added by oil base. Try: 1. thinning the water base a little bit; 2. sanding between each coat, or every other coat; 3. more than 3 coats. I remove brush marks with 400 grit and prefer buffing rather than sanding through all those finer grits you are using.
 
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