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White streaks in Shellac

6/29/17       
Michael Member

Hello,

After spiriting off (with naphtha), I am seeing white streaks in my work. This is likely the first time I have used Methyl Hydrate as my shellac solvent rather than the ethanol I usually used. Could the white streaks be because I used Methyl Hydrate and perhaps here is too much water content in the methyl hydrate? By the way I am in Canada and Methyl hydrate is the name of the widely available low-cost alcohol. Why else could I possibly be seeing white streaks? I've seen this before when I was working on a shellac project in the middle of a wet snowy winter and at that time I prevented it by moving indoors to a warm room and re-shellaced the project and the white streaks disappeared. So now, in the middle of summer why would this problem re-occur? I am suspecting it is the low-cost alcohol (Methyl hydrate). I am "generally" following the shellac procedure from Bob Flexners book understanding wood finishing. Any suggestions? Thank you kindly,

Michael


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6/29/17       #2: White streaks in Shellac ...
rich c.

Any white in a finish is a moisture issue. High shop humidity and quick solvent flash off are likely issues.

6/29/17       #3: White streaks in Shellac ...
Michael Member

Thank you for your helpful advice. I don't think it could be shop humidity becuse it is a very hot and dry weather now although it may have cooled in the evening when I was applying the shellac a few days ago and then perhaps a little moisture in the evening air made its way into the finish. Really not sure. I am using Naptha for spiriting off. Is it because the Naptha is evaporating too fast? I tried paint thinner instead but the streaks still appeared. It looks great just before the spiriting off step when there is lots of mineral oil on the work- nice and glossy and perfect looking. It's just when I rub off the mineral oil that the streaks re-appear. I mixed up a new batch of shellac last night using ethanol this time and I will give it another try overtop my old shellac with the streaks. This time I will apply more thinner coats rather than heavy coats - maybe that was an issue that caused the streaks. Hopefully it will work better this time. Thanks again. If any one else has any thoughts that would be great. Thanks once again!

6/29/17       #4: White streaks in Shellac ...
rich c.

I'd wash off what you have on there, and start over. Attached is an old discussion on here about blush in shellac.

WOODWEB Knowledge Base Article

6/30/17       #5: White streaks in Shellac ...
Kit Mosden Member

I had a similiar issue and found that switching to a better quality alcohol cleared up the problem. Upon recommendation from my
shellac supplier I now only use Sunnyside Alcohol.

6/30/17       #6: White streaks in Shellac ...
Michael Member

Thanks again Rich!

I read your really helpful post about controlling Shellac blush. Really appreciated! I will give some of these suggestions a try. First with a little heat from a hairdryer (or heat gun) with care not to heat it up too much to avoid damaging the finish and wood and veneer. Secondly I will try with my newly mixed shellac that was diluted into Ethanol (as opposed to the one that gave me all the blush problems with Methyl Hydrate). Then if all else fails I will wipe it all off and start again.

Thanks again!

Michael

6/30/17       #7: White streaks in Shellac ...
Michael Member

And thank Kit for your suggestion too. As I mentioned, I will try my better quality alcohol (ethanol) that I purchased specifically for Shellac from Lee Valley Tools here in Vancouver. Its a little expensive but, as you mentioned, it likely could be the best solution to this problem. Thanks once again!

Michael


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