#7
  
I haven't checked in here in a long time....cause I've been remodeling the house.  No fine woodworking stuff.  Well I finally got around to putting together a table top from the leaves of my grandmother's mahogany table (otherwise destroyed from sitting in a damp shed).  I can't believe how many things I have forgotten (kind of messed up some of the wood by not setting up a plane properly, etc.).  Anyway I have a finish problem.  I was using Arm-R-Seal satin with a foam brush, but kept on getting friction marks and brush marks.  I was sanding in between coats with 220 - some high performance paper that I think made problems worse because I can also see sanding grooves.  But anyway I'm left with marks in the finish about 2 coats down from my current fifth coat of finish.  How do I go about fixing this?  Can I sand to the offending layer?  What grit do I use to remove the offending stuff?  Is it alright to sand crossgrain once the basic finish coat is even?  I've finished tons of stuff and never had a problem like this.  Am I missing something?
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#8
  Screwed up finish dustmight I haven't checked in...
I wouldn't use a foam brush. I've never liked the results.

220 is too aggressive for sanding a finish. Very lightly with 320 to start. Then probably wet sand with 400-600 if you wanted it nice.

Did you use a backer for the sandpaper?

I'd probably sand it off and start over.
Mark

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#9
  Screwed up finish dustmight I haven't checked in...
(05-14-2019, 09:40 PM)dustmight Wrote: I haven't checked in here in a long time....cause I've been remodeling the house.  No fine woodworking stuff.  Well I finally got around to putting together a table top from the leaves of my grandmother's mahogany table (otherwise destroyed from sitting in a damp shed).  I can't believe how many things I have forgotten (kind of messed up some of the wood by not setting up a plane properly, etc.).  Anyway I have a finish problem.  I was using Arm-R-Seal satin with a foam brush, but kept on getting friction marks and brush marks.  I was sanding in between coats with 220 - some high performance paper that I think made problems worse because I can also see sanding grooves.  But anyway I'm left with marks in the finish about 2 coats down from my current fifth coat of finish.  How do I go about fixing this?  Can I sand to the offending layer?  What grit do I use to remove the offending stuff?  Is it alright to sand crossgrain once the basic finish coat is even?  I've finished tons of stuff and never had a problem like this.  Am I missing something?

If you are seeing sanding marks below the surface you will either need to accept it, sand it down to at least that level, or strip it all off and start over.  If your finish was just topcoat and no stain or dye to start with, I would strip it off with chemical stripper.  As durable as ARS is to most stuff, it comes off with stripper very easily, at least stuff that hasn't fully cured has for me.  

A guy who hasn't been here for awhile, Richard D., showed a beautiful table he made with an ARS finish he applied with a foam brush.  I have good luck with a foam brush, too, on large surfaces IF I first thin it about 25% with real mineral spirits.  

For your project, I would start with gloss ARS and put on 3 or 4 coats, sanding with 325 or 400 grit between coats just to take off the dust nibs.  Once you see a complete film with no dry areas I would let it sit for a couple of days and then sand it dead flat with 400 or 600 grit on a ROS.  Then wipe on a couple of coats of satin to finish or use gloss and rub it out to satin after 10 days or more.  

John
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Screwed up finish


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