Wenge Grain-Filling Discoloration Problem

      Why is the grain turning a milky white after filling with a high-solids 2K poly? June 18, 2009

I am building a solid wenge table and the client wanted a filled clear finish. I did some samples about two weeks ago with ML Campbells Eurobild, then topcoated with Magnamax. It looked excellent and the client approved the sample. I just looked at the sample and it appears to have turned white in the grain filled pores. If anyone has any suggestions with filling wenge or Eurobild I'd love to hear it. I need the finish to stay clear, no haze or cloudiness.

Forum Responses
(Finishing Forum)
From contributor R:
What did you use to fill the grain? Just the Eurobild or did you use a paste filler of some kind? I guess I am asking what your finish schedule was.

From contributor Z:
We just did a wenge desktop. We used a MLCampel product called Level. It worked very well. We did not fill the grain completely. We used two coats of Level and sanded down and then our topcoat which was two coats of Duravar. The finish ended up very smooth - not completely filled, but enough for a desk top. With a couple more treatments of Level I'm sure you could fill the grain all the way.

From the original questioner:
I basically sanded the solid wenge to 150 then sprayed one heavy coat, let dry for one hour, applied a second coat(without sanding first coat), let dry one hour then sprayed third coat(without sanding). I let this dry for 24 hours then sanded wood flat and applied one full wet coat Magnamax satin. It looked incredible, flat clear and no grain showing. Two weeks later this original sample piece looks cloudy and all the deep grain has turned white.

I have read that oily exotic woods should use euro exotic wood sealer first before applying the sealer, but I thought this might only affect adhesion. I am only filling the grain in with Eurobild, no other paste filler or stain on the wood. I am not wiping anything on between coats. The ML Campbell reps are a bit confused and we sent the sample to their lab. We have worked with wenge a lot and normally topcoated with Magnamax and never had any problems.

From contributor R:
For a closed coat finish on an open pore wood like wenge I would use polyester to fill the pores (Isolante first coat for adhesion on oily wood and then polyester). I would then topcoat with a 2k urethane like Akzo Nobel Ora Verde or Milesi. I wouldn't personally use a CV type finish over the polyester as I believe I get better adhesion with the 2k urethane. Campbell’s Level sealer is also a good product and I think I would use that if going with CV. As far as the white pores the only thing I can think of is high moisture content or high humidity the day you sprayed or it could be an adhesion issue due to the oily wood.

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