Finish Defects with Waterborne Over Oil Stain
A finisher gets advice on how to fix blemishes caused by applying two finish coats that don't play well together. January 14, 2008
Question
I have a problem getting a nice finish on a few cherry bathroom cabinets (solid cherry legs, rails, and doors; veneer side panels). I put on a natural Watco stain, dried for two days, and used two coats of ML Campbell Ultrastar WB, sanding 320 between coats. Close up you can see some tiny blistering or stars, sort of with the grain. I noticed the veneer panels are fine. Is the wood or the finish the problem?
Forum Responses
(Finishing Forum)
From contributor R:
What is the Watco natural stain doing for you? My suggestion would be to eliminate it from your coating process. I am not sure that a waterborne can coat over the Watco oil without a shellac misting.
From contributor L:
Whenever I use the Watco Danish oil stain, I allow it to dry for 3 full days (72 hours). I usually put MagnaMax or Krystal on it. You might need a barrier coat - maybe shellac or a vinyl sealer.
From the original questioner:
It seems there is something in the Watco that is venting through the finish. I don't usually use Watco, but I successfully coated over tung oil and others before! So how do I fix it?
Option 1 is to forget about it for 2 or 3 days, sand and recoat. Option 2 is to buff with fine steel wool and wax.
From contributor D:
I too am curious - what did a clear stain do for your finish? Were you looking for the color/grain pop of solvent based finishes? If that was your motivation, I feel that dewaxed blonde shellac would have been a better choice under WB coatings. That said, I would sand the finish and mist a coat of shellac as a barrier, and then apply my WB finish.
Note: be careful when applying shellac over a WB coating. The alcohol will sometimes soften or lift the WB coating. I have done many repairs using this method with great success.
From contributor P:
I think you need to let it sit longer and seal with shellac. I use the Watco natural on cherry furniture sometimes. Sometimes I topcoat with Target's CV, which does well, and their poly, which does very well. I've used the MLC Duravar on some things lately and it's done well.
With the Watco, which I use on half the furniture I do, you have to let it dry and seal with shellac. I think using a water-based over oil without shellac is asking for trouble. I'll typically let a piece sit around for at least four or five days, even a week or two if it's rainy during that time. If I'm using the Target CV or poly, then I use their WB shellac. I've only used the Duravar a couple of times, but I used Zinnser's dewaxed shellac and so far, so good.
From the original questioner:
I used the natural Watco to bring out the grain and color and it does a good job at that. I have not used shellac before. I'm re-sanding the cabinets today and recoating them with Fuhr 250 because the Ultrastar was also running on the vertical surfaces. Yes, I did a test piece and it looks great.
From contributor T:
WB on cherry makes it look anemic at best. Amber shellac works well to lock in some color before finishing. It's easy to apply and it dries quickly. Watco works as well, but... Watco is an oil/varnish blend and there's not much of either in the finish. It soaks in well and it also bleeds back out as it cures. If you use Watco, you need to go back and re-wipe several times in the 3 or 4 hours after it's applied. If you don't, you'll get little lumps of cured finish over the larger pores. Looks very much like what you've described. So next time... As for this time, I think you're on the right track.
From the original questioner:
Well, it all turned out very good in the end - that's what counts. And I learned a lesson or two. Thanks for all the help. I think contributor T is right on as for the cause and the fix.
