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Building Tips and technical articles. => Building techniques => Topic started by: Kirm Dog on March 07, 2006, 06:59:35 AM

Title: Minwax Acrylic Polyurethane
Post by: Kirm Dog on March 07, 2006, 06:59:35 AM

  I just tried the Minwax Poly on a test piece of balsa and had some startling results. The grain was raised so bad that I question weather I did something wrong. I had sanded with 320 grit paper then applied the Poly with a brush. I was going to use this to stick down some carbon mat but I think I will stick to dope.
  Anybody else ever have this problem with Acrylic Poly? Should I try sanding again and apply a second coat?

Don Kirmess

Title: Re: Minwax Acrylic Polyurethane
Post by: Russell Shaffer on March 07, 2006, 07:03:38 AM

Is it the water based variety?  That would explain the grain.  Russell

Title: Re: Minwax Acrylic Polyurethane
Post by: Kirm Dog on March 07, 2006, 07:40:21 AM

Yes it is water based.

Title: Re: Minwax Acrylic Polyurethane
Post by: Bill Little on March 07, 2006, 10:48:43 AM

Hi Don,
I would sand it with 320 or so and hit it with another coat.  That should make it smooth and sealed.   Hit it with the 320 or 400 when the second coat is cured and apply your CF!  ;D

Title: Re: Minwax Acrylic Polyurethane
Post by: Kirm Dog on March 07, 2006, 06:03:38 PM

Thanks Bill, I'll give it a try.

Don

Title: Re: Minwax Acrylic Polyurethane
Post by: phil c on March 08, 2006, 11:16:27 AM

you can save yourself a lot of sanding by putting on 2-3 coats before sanding.  Usually by the third coat the film has pretty well developed and you can sand it smooth without going through.  If you sand through the film, it opens the wood up to more grain raising on the next coat.

Title: Re: Minwax Acrylic Polyurethane
Post by: L0U CRANE on March 12, 2006, 02:52:54 PM

I'd heard that the poly material can be quite heavy. Thinning it 2 or 3 to 1 with rubbing alcohol makes coats lighter, reportedly, and isopropyl evaporates quicker than water.

That may spare some of the grain rise, and keep each coat lighter.

Did I mistake what I think I'd heard?

Title: Re: Minwax Acrylic Polyurethane
Post by: john e. holliday on March 19, 2006, 07:05:40 PM

My experience with water base Poly-Urethane is to sand after the first coat has cured for at least a day.  It soaks into the wood and makes it stiffer/harder.   Then it does not take so much on second coat.   DOC Holliday