grey shellac effect?

Sometimes when I am coating some wood with warm shellac flakes I get a patch of greyish finish. If I put more shellac over it, it goes away but I was wondering what I was doing to contaminate the mixed shellac. I apply by brush. Thanks Ted
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That sounds like moisture, causing "blushing".
Blushing is possible with shellac and lacquer if moisture gets trapped under the finish. Just as you've noted, the blush is often easily removed by applying more finish. I've removed lacquer blush by spraying a very thin "flow coat", which reconstitutes the finish and allows the moisture to leave.
Is your alcohol contaminated?
If not, maybe the warm finish is attracting moisture on higher relative humidity days.
With lacquer and shellac, I shoot for at least a 15 degree F (20F is better) spread between the temperature and dew point.
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B A R R Y wrote:

drying out? I give it a good wipe before I use it normally.

It was actually 16o C

Thanks, Ted
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You can't remove all of the water with a wipe. Use alcohol to keep the brush from drying out or stick it in a zip loc bag.
R
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On Fri, 23 May 2008 06:09:54 -0700 (PDT), RicodJour

Or just let it dry and soak it in alcohol before the next use. Shellac will totally redissolve when alcohol is reintroduced.
I don't clean my shellac brushes at all.
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"ted" wrote

Don't bother, no need to put a shellac brush in anything... nice thing about shellac, go ahead and let the brush dry between coats, then stick it back in the shellac for a few minutes and it'll be ready to use again.
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Shellac is insoluble in water. If you put the brush into water the water will dilute the alcohol and the shellac will immediately harden on the brush. If that isn't happening to you then either you're not using shellac, or you're not putting the brush into water.
I use a ladle to transfer shellac from the can to the pot where it's diluted for use. That way the rim of the can stays lean. I tried cleaning the ladle with water *once*.
--
FF



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On Fri, 23 May 2008 22:41:48 +1000, ted wrote:

Ouch! Don't do that! Shellac and water are not a good combination. Store the brush in alcohol. Or better yet, put the shellac on with a pad and toss the brush.
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ted wrote:

You can probably tell I'm new at this. Want to check on terminology here. Your comments about alcohol: I use Methylated Spirits to make the shellac up. Are you calling MS the alcohol or should I be using something else? I just left a brush out of the water to test the re-soften hint. Thanks for all your comments, Ted.
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wrote:

Hi Ted,
PMJI, but...
The Methylated Spirits is appropriate. (It is simply two different types of alcohol mixed. One is ethanol, the other methyl alcohol. The latter is poisonous. If they sold pure ethanol as a solvent, folks would drink it...)
But please say something more about why you believe that the MS was not contaminated.
I ask because such "contamination" can happen more easily than you might think. The situation you described does seem to indicate "blushing" (as others have said) but that can happen in some subtle ways.
Alcohol l-o-v-e-s water, and it is difficult (and therefore expensive) to remove water from alcohol. So (virtually) any alcohol you can buy will have (some) water in it before you open it.
But then, just leaving a container of alcohol open on the bench on a humid day can cause problems.
In fact, the tendency of the alcohol to absorb water from the air, together with the water on the surface of your work on such a humid day, might be enough to cause the "blush."
All the best,
--
Kenneth

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Kenneth wrote:

Hi Kenneth, seems that my habit of popping brush in water seems to be the culprit. It only happens occasionally so I am presuming it's when I don't dry the brush properly before I use it again. Saves me a hassle not to have to dry it so I'm happy. Thanks for everyones comments, I'll do it properly from now on. Cheers, Ted
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wrote:

Hi Ted,
I read of your "water popping" after I posted... 'sorry.
Yup, that would certainly be the likely source of the problem.
All the best,
--
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But surely it didn't stay soft in WATER, did it?
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FF

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Yep Ed.
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