Replies

1. 
   CStanford_ | Apr 10, 2001 02:00pm | #1

   *
   Polyurethane is a type of varnish. It's frankly a little hard to imagine that 15 coats of anything will not provide enough protection. What are you doing with the table? Are you sure that your expectations or notions about what finishes can and can't do are realistic?

   If you used a 50/50 varnish/solvent mixture then the fifteen coats will be about as good as it gets. What kind of varnish did you use? Spar varnish in a 50/50 mix should have given incredible build and plenty of protection. For that matter any other varnish should have as well.

   Something sounds out-of-whack.

1. 
   Danford_C._Jennings | Apr 10, 2001 05:24pm | #2

   *Phil,I agree with Charles but, I would like to add that assuming that you used a true varnish it will take anywhere from 4 - 6 months to cure depending on climate. Varnish will never totally cure because it is elastic. Since we don't know how your definition of "recent" and the specifics of the durability problems it would be difficult for me to make further comment. I will say that even polyurethane will scratch. FWIW.Dano

1. 
   Gretchen_ | Apr 10, 2001 09:17pm | #3

   *What "varnish" did you use for your 15 coats? Unless you went on a search for non-poly, you probably have poly on it anyway. In my experience you must go to a reputable paint store and ask for non-poly to find it. All that said, you have enough varnish/protection on it without adding a layer of plastic.

1. 
   Howard_Acheson | Apr 10, 2001 11:42pm | #4

   *A friend who is a profissional finisher and I tested the build on brush applied full strength McCloskey varnish compared to a wiped on 50/50 mixture of the same varnish and naphtha.The wet film thickness and the dry fill thickness indicated that it took between 3-5 coats of wipeon to equal one coat of full strength brush on. This was without sanding between coats. We did the test three times to get the results. The wet film thickness was measured with a gauge used for that and the dry was peeled off and a measured with a thickness gauge.On average, it would probably be not to far off to figure 4 coats of wipeon to one coat of brushon. I generally use 8-10 on my projects.

1. 
   Gretchen_ | Apr 11, 2001 01:07pm | #5

   *Good information. Thanks. I had wondered if 8-10 coats was overkill on my part.

2. 
   Cleric626 | Sep 30, 2013 01:37am | #6

   Please help!!

   I too have the same question... My project is as follows a 1/4 BIRCH Hardwood Plywood that I refinished a table top with and added 1x2 Pine Board to finish the edges with. Now I have stained the table top as well as put 7 solid coats of Cabot Gloss Spar Varnish on the table already which is an oil based varnish. (No mixing 50/50 mineral spirits with varnish) Just straight coats of varnish onto the table top and then waiting 6 to 8 hours for it to dry properly. And yes I am using a 400 grit sandpaper to take out bubbles and miniscule dusty crap so that the table is smooth for the next application processes. So here is the question, Can I apply a oil based polyurethane gloss on top of the already dry Spar gloss varnish with out adding some weird coloring in the process. I want this table to be durable to toss into a monsoon (LOL not really just a joke)

   
1. 
   HowardAcheson | Sep 30, 2013 12:56pm | #7

   Poly Varnish

   First, this thread is 10-12 years old.  It is best to start a new thread to prevent confusion to those reading it.  Second, polyurethane is a varnish.  It's just a varnish made with urethane resin instead of alkyd resin. 

   So, yes, you can apply an oil based poly varnish over a non-poly varnish.  Because poly varnish has much less adhearence than non-poly varnish be sure you thoroughly scuff sand the surface with 320 sandpaper.  Let me say though, non-poly varnish has a nicer, more clear appearence than poly varnish. Poly varnish tends to look cloudy and becomes amber quite quickly.  I would just leave the non-poly finish alone. It's more than durable enough once you let it fully cure for six to twelve weeks.