Replies

1. 
   RSRose | Sep 06, 2002 10:45pm | #1

   Wanda,

   I really don't get it. You have posted question after question asking about the most basic and rudimentary decision making of mechanical processes, yet you otherwise describe quite a bit of knowledge and experience about woodworking, processes and tools.

   There isn't a can of urethane varnish that doesn't recommend the grit of paper to use when scuffing between coats. But your question, "is it absolutely necessary to sand between coats?" what kind of response do you think you'll get to that?

   If you had asked for basic advice about the process, and didn't know anything about it, various people would have told you to consider sanding if dust particles had settled on the finish or if more than 2-3 days had passed between coats.

   But "is it absolutely necessary?" Just what are you looking for in the way of advice here? There are no absolutes in anything. You seem to want people to eliminate every uncertainty for you.

   Rich

   
   

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   Edited 9/6/2002 3:47:08 PM ET by Rich Rose

1. 
   Gretchen | Sep 07, 2002 05:43am | #3

   How pleasant Rich.  Gretchen

1. 
   RSRose | Sep 07, 2002 06:38am | #4

   It was not meant to be unpleasant, Gretchen. Just honest.

   This is a continuation of other posts that just string the responders along in an endless spiral of demanded reassurances of absolutes. And then disregard for advice solicited.

   Rich

2. 
   Paul_Snyder | Sep 07, 2002 01:23am | #2

   The worst case scenario is that the poly will "delaminate" in patches and crack/peel. Sanding between coats gives the finish a mechanical bond since there is no chemical bond between coats of cured varnish/poly. It's up to you if that makes it "absolutely necessary."

   I generally sand with a 3M sanding sponge, though you can use 320 grit for wipe-on finishes or 220 grit for full strength brush or spray applications. Sand lightly - just enough to smooth the finish and dull the sheen.

   Here's an article by Bob Flexner that provides some good guidance on getting a nice looking finish - http://www.popularwoodworking.com/features/finish5.html

   Paul

   F'burg, VA

1. 
   wanda20011 | Sep 08, 2002 02:59pm | #6

   Hello Paul,

   Thank you for your response. That's exactly what I wanted to know. :)

   Wanda

3. 
   rickjones5 | Sep 07, 2002 08:18am | #5

   Poly is a varnish which is a reactive finish.  Reactive finishes do not disolve the surface of the previous coat as evaporative finishes ( lacquer, shallac ) do.  Poly does not like to stick to self.  Therefore, you must scuff.  400 should do.  However poly usually needs to be leved between coats, especially if the surface is to be rubbed out. 150 would be ok.

   rick

4. 
   peterg62901 | Sep 08, 2002 03:09pm | #7

   The best answer is to read the can.  I have used fast dry water based poly that doesn't  need to be sanded if you apply the next coat within 24 hours. 

5. 
   Sancho | Sep 08, 2002 09:34pm | #8

   Check out a book by Jeff Jewett called "Great Wood Finishes" it should anwser all of your questions about finishing.

    Darkworksite4: When the job is to small for everyone else, Its just about right for me"