I am new to using shellac. Is it safe to use Zinsser Bulls Eye amber cut to 1lb as a wash coat/sealer later to be finished with lacquer. Zinsser emailed to say Bull Eye contains “a small amount of naturally occuring wax”. I understand I am use 3 parts alcohol (Bekhol from L. Valley) to 2 parts Bulls Eye to get the 1lb cut.
The wood being sealed is cherry.
I cannot easily find Zinsser’s Seal Coat in Toronto that is 100%wax free.
Appreciate you advice.
Mark
Replies
Mark,
Shellac that contains wax, like the Bullseye, isn't a problem under solvent based lacquer. The manufacturer's warning concerning adhesion problems extends to oil-base polyurethane and some waterborne finishes. Zinsser has a tech sheet on the Bullseye shellac at this link (.pdf file) - Zinsser Bullseye Shellac.
If you need to dewax the Bullseye shellac, you can pour it into a glas jar and let it sit for 3-5 days. The shellac will settle to the bottom of the jar and you can decant the wax-free shellac from the top of the jar. Here's a "before" and "after" example;
Shellac - just poured
Shellac - wax settling
Paul
Dewaxing that way does not remove all the wax. A lot, but not all. You can do a little better by refrigerating the bottle. I'd guess there's still a half to 1% wax still present when it all settles. I'd still be a little reluctant to use it under poly finishes. It does improve the appearance and gloss and probably gives better water resistance that way.
Bob,
In the jar on the right, the wax has settled to the bottom. The shellac in the upper portion is very clear and virtually wax free. If you decant the shellac from the jar without getting any of the waxy portion, you will have dewaxed shellac.
Commercially dewaxed shellac contains around .2% wax. Dewaxing using this technique is as effective as the commercial process as long as you're careful to avoid the wax. I have tried the refrigerator/freezer technique and did not see any improvement in the separation.
Paul
Yes, I realize what you did. But, the wax has a range of molecular weights. Not all of it will ever settle out. Some remains in suspension forever. It has much better clarity with the majority of the wax removed by settling, but it is still not as good as commercially dewaxed shellac. It also has a lot more waste.
Would centrifuging get more of it, or is the LMW fraction just too close to the same density as the shellac?
I don't know if centrifuge would extract a much higher percentage of wax. Some of the wax is slightly soluble in alcohol. Almost everything is *slightly* soluble in everything else. It would compact the wax layer and give you more clear shellac. Less waste.
I have some waxy shellac (seedlac) that has never separated after leaving it sit for a year. My experience has been that not all shellac can be dewaxed by settling.
Removing wax as Pauls suggests leaves so little wax that it will not affect the adhesion of polyurethane varnishes. No need to get 100% of the wax out.
Bob,
You're right that a lot of good shellac goes out with the waxy portion; but in an "emergency" it's a solution. Or for folks that rarely use shellac and just want/need a little dewaxed. I only suggested it since he said he couldn't find Seal Coat locally. In Canada, folks can order dewaxed shellc flakes from http://www.woodessence.com
And you're right that a little of the wax remains in suspension. Some of the wax particles are so small that they are held in suspension by the effects of Brownian motion. But the quantity of wax in this category is minute compared to the wax that does settle; it's not enough to cause concern.
Paul
You can filter it through a coffee filter.Gretchen
From a previous discussion:
http://forums.taunton.com/tp-knots/messages?msg=16279.6
VL
Any paint store or hardware store that carries Zinsser products should be able to order their Seal Coat and get it within a week or so.
John W.
You can buy dewaxed shellac flakes online from Wood finishing supplies.com
Easy to mix a batch, flakes last forever in a sealed bag. You can mix what you need and store the flakes for next job.
mike
Lee Valley has
I may buy dewaxed shellac flakes in Lee Valley store:
http://www.leevalley.com/en/wood/page.aspx?p=72634&cat=1,190,42942
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