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Varnish not sticking

My wife and I have been refinishing a dresser and have run into a problem.  The top and sides are made of wood veneer (walnut?).  We vigorously sanded the dresser to remove prior finishes and then stained it using Minwax Wood Finish Oil-Based stain.  

 

We are now varnishing the top and sides with Minwax Polyurethane Clear Gloss Oil-Based varnish.  The sides are taking the varnish fairly evenly, but the top surface is not.  Initially, it goes on as a smooth, thin, uniform coat, but within 30 seconds, it begins to pool and circles of wood become exposed.  I was hoping the second coat would help even things out, but it appears the same as the first.  I can't figure out why it is not sticking.  It is 70% humidity outside - perhaps the wood is taking up moisture from the air and rejecting the oil-based varnish?  I've attached photos below.  Please help!

 

Before varnish:

Before varnish

 

After first coat of varnish has dried:

photo 1.JPG

 

Soon after second coat of varnish has been applied (still wet):

photo 2.JPG

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Posted 2012-07-21T18:42:00+0000  by spritemv spritemv
 

Hey spritemv,

 

Thanks for joining us on the community and equal thanks for posting the images!

 

The Minwax Oil-Based Polyurethane could be bubbling due to several factors:

 

  • the adhesive used underneath the veneer could be reacting to the polyurethane, giving you a uneven and drying issues
  • the vertical surfaces aren't against gravity (i.e. held there on a horizontal surface) which is leading you to good results on that surface

If you used contact cement or a similar oil/solvent-based adhesive for your veneer top, the top coat of polyurethane as stated earlier could even be loosening the adhesive underneath. Since veneer is a thin material, this could be a real possibility of giving you the failure now.

 

You did your homework on sanding the dresser for prior finishes but also remember to prep sand with a 220 or slightly higher grit of sandpaper to ensure the first and in-between coats will adhere properly to the surface. This is also crucial to make sure the 2nd coat will be effective. 

 

The humidity maybe a factor but after 4-6 hours, the top coat of the polyurethane should be drying at or near completion.

 

My thoughts are on the nature of the product you are using against what is already on the surface. With that said, I would remove the polyurethane as best as you can. I realize this will effect the stain already on the top, but after coating it with a water-based polyurethane, this should get rid of any drying and sticking issues for the dresser top.

 

Let us know if you are aware of what was used as an adhesive to apply the veneer to the top as well as if you lightly sanded and cleaned the surface before application of the polyurethane.

 

It looks like a great dresser that you are working on, and I know you've done so much work already. 

 

Hope to hear from you soon,

aboveaveragejoe

Posted 2012-07-21T19:19:15+0000  by Joseph_HD_ATL

We purchased the piece used, so I'm not sure what type of adhesive was used.

 

We sanded it with a larger grit paper, followed by 220 grit prior to staining.  The surface was cleaned prior to staining and prior to applying the polyurethane.  In-between polyurethane coats, we very lightly sanded it with 220 grit paper and cleaned the surfaces again.

 

Would you recommend removing the polyurethane simply by sanding again?  I presume I'll have to restain it afterward?

Posted 2012-07-22T00:02:24+0000  by spritemv

 

spritmv,

 

The extent of your sanding could not have been too agressive, otherwise you would have been through the paper thin veneer ( as little as 1/64th of an inch). If I could hazard a guess, it is that over the years the owner of your cabinet had been using some wax or silicone containing product as a polish. I fear that some of the residue remains on the top surface and is causing the new urethane to pull back as if beading. The fact that the sides are not beading would be attributable to the likelyhood that only the top would have been periodically waxed.

I used to hate "Pledge" for exactly this reason. Years ago it contained wax. Often I would be hired to varnish kitchen cabinets only to discover that the housewife had been "pledging" them over the years. It the wax was not removed, a situation similar to what you are experiencing would occur.

 

What to do now? You have no other choice than to strip away the urethane and get back to wood. I would then use fine steel wool and lacquer thinner to throughly clean the surface, rubbing with the grain. I personally would not have used sandpaper at all in the inital stripping due to the thinness of the veneer. The final cleaning of the stripper would have been with lacquer thinner and steel wool.

 

You will probably have to re-stain the wood. After letting the stain thoroughly dry, proceed again with the urethane.  As a hedge against further problems, you might spray the dried stain first with a coat of Zinssers Clear Shellac. This shellac is de-waxed, unlike Zinssers brushing version. This is important because de-waxed shellac is compatible with almost any finish and almost any finish is compatible with it. Urethanes are NOT compatible with regular shellac. De-waxed shellac is not only a superb bonding agent, but it also is a super sealer. The first coat of the urethane will also look better over shellac.

 

You might also consider using the spray version of Minwax Urethane. I have had excellent results using it on past furniture projects of mine.  It can leave a factory like finish with no brush marks. Use long, straight overlapping strokes. It must be overlapped enough so as to avoid a striped look. I like to heat the cans before spraying. Place the can in a pot of water as hot as it comes out of the tap for several minutes. This builds up the pressure in the can. Also, being an oil product, it flows much better when warm.  Be sure to shake all the water off the can. There is nothing more aggravating than having a drop of water drip onto your nice new varnished top!

 

Hope this is of help.

Posted 2012-07-22T05:03:50+0000  by ordjen

Thanks for the great advice!  I ended up using steel wool and lacquer thinner to strip of the polyurethane and stain.  I did end up carefully sanding a bit as there were some blotches of remaining stain.  The Zinssers stuck like a charm this evening.  I'm planning on brushing poly over the Zinssers tomorrow.  Do I need to sand the ZInssers prior, like I do between coats of varnish, or can I brush varnish directly on it?

Posted 2012-07-24T02:42:01+0000  by spritemv

 

You do not need to sand the Zinssers for the sake of adhesion, only if it has some roughness. If so, a light sanding with 320 grit paper will suffice. Just wipe off the dust and proceed. If you stay within the time parameters of the urethane, usually after dry, but not longer than 12 hours, you do not need to sand it either, unless some schmutz has gotten onto the surface. Once a urethane has cured, after 12 hours or so, it is best to give a scuff sanding for the sake of adhesion.

Posted 2012-07-24T03:45:17+0000  by ordjen

The dresser is finished.  The varnish looks great.  Thanks so much for the advice!

Posted 2012-07-26T23:55:02+0000  by spritemv

 

spritemv,

 

Glad to here it turned out OK. When you posted that the shellac had stuck, I knew that it would be fine. One of my prime uses of de-waxed shellac is as a bond coat to assure that the final coat of paint or varnish will stick. A brushing version of de-waxed shellac is available from Zinsser under the name "Seal Coat". My Home Depot ,unfortunately, does not carry it.

Posted 2012-07-27T04:36:37+0000  by ordjen
Ordjen,

You absolutely "Nailed It" once again!

Taking spritemv through a fix for this problem took both skill and product knowledge.

I've said it before ... we a so lucky to have you as a contributor!
Posted 2015-12-08T23:09:39+0000  by Pat_HD_ATL
 
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