Novice question – My only experience with shellac has been Zinsser SealCoat which is, I believe, a 2# cut of very blond shellac with a 3 year life span. I’ve wiped it and padded it – I think the padding seems virtually identical except it wastes less shellac(?).
I beleive Zinsser has two BullsEye Shellacs (blond and amber) which I assume are a heavier cut (I couldn’t find the info and they haven’t replied yet) and designed to provide a finish coat, whereas the SealCoat is a sanding sealer.
Questions:
1) Are there any pragmatic advantages to mixing my own shellac from flakes for someone who does a table top (usually after sanding off the original finish) twice a month?
2) Is SealCoat the same as 2# cut shellac? Does it have anything that makes it not work as a final coat other than the fact that it’s only a 2# cut?
3) Do multiple coats of a 2# coat work just as well as fewer coats of a 3# or 4# cut?
4) If I do buy a pre-mixed finish coat shellac (depending on the answers I get), should I get something other than the Zinsser product?
Thanks!
The Wood Loon
Acton, MA
Replies
Questions:
>> 1) Are there any pragmatic advantages to mixing my own shellac from flakes for someone who does a table top (usually after sanding off the original finish) twice a month?
The advantage to mixing your own is that you know how old it is. Zinsser amber and clear have a three year shelf life.
>> 2) Is SealCoat the same as 2# cut shellac? Does it have anything that makes it not work as a final coat other than the fact that it's only a 2# cut?
Zinsser SealCoat IS shellac and only shellac. It's 2# cut which is the best cut for brushing shellac. In other words, you can use the SealCoat right out of the can. The other two Zinsser shellacs should be cut from their out of can 3# cut to a 2# cut for brushing and padding.
>> 3) Do multiple coats of a 2# coat work just as well as fewer coats of a 3# or 4# cut?
Yes, but as I said above, the ideal brushing cut is 2# - 1 1/2#. So you will find shellac easier to use if you cut the clear and amber to 2#.
>> 4) If I do buy a pre-mixed finish coat shellac (depending on the answers I get), should I get something other than the Zinsser product?
Zinsser is the only consumer seller of premixed shellac in the US.
One final note, if you plan to top coat your shellac with some other finish, you MUST use a dewaxed shellac under oil based poly varnish or any waterborne acrylic finish. In other words, only SealCoat can be used under poly and waterborne poly.
>> I beleive Zinsser has two BullsEye Shellacs (blond and amber) which I assume are a heavier cut (I couldn't find the info and they haven't replied yet) and designed to provide a finish coat, whereas the SealCoat is a sanding sealer.
There is no technical difference between the two BullsEye shellacs and the SealCoat shellac except that the two Bullseyes contain their natural wax while the SealCoat is dewaxed. The "sanding sealer" is just a marketing ploy. Any shellac is a sanding sealer.
WOW! Detailed answers from two Finishing Maestros, Howie & Steve, within a dinner hour of my original posting! Thank you, again, for your superb generosity. Your answers fill in the gaps of my knowledge and I feel better about the decisions I've made so far regarding shellacs. I will stick with SealCoat and padding for a while. This summer I might try some flakes, but I must admit it really is convenient to just open a can! Thus far I have not run into a situation where I wanted the shellac to be amber (or darker), so the color has not been a problem. But I can see where it might become desirable. Of course then I run into issues of who has the best flakes, and on and on goes my education. Thanks again, teachers.Doug
The Wood Loon
Acton, MA
Hi GDH2,I'm certainly not a finishing expert, but you'd be surprised how easy it is to mix up your own shellac. I always read that it would take overnight to dissolve, but for me it never does. I mixed up a tiny 4 fluid oz of 2lb cut amber shellac earlier this evening and brushed a couple of coats already.Best regards,
Paul
Yes, Seal Coat is 2# cut blonde shellac (though compared to some flakes that lighter I'd call it more of a dirty blond) Its principal characteristic is that it is dewaxed, having been filtered to remove the natural wax that occurs in shellac.
The two other liquid shellacs made by Zinsser are Amber (which is made from orange shellac) and Clear (which is made from shellac which has been chemically bleached to eliminate more color. The bleaching process reduces the durability of the Clear shellac compared to the other varieties. These are most commonly found as 3# cut mixtures, which is heavier than most people find comfortable to use. (It is, (or has been) possible to find these shellacs in 4# and 5# cuts.)
All three flavors are equally shellac, and each is suitable as a top coat. The only special property that the Seal Coat has as a "sanding sealer" is that because it is dewaxed some finishes, such as polyurethane varnishes and waterborne finishes will adhere well. These finishes don't adhere well of shellac with wax. Tradtional resin varnish adheres to shellac with or without wax. The dewaxed shellac actually sands a bit less easily than the shellac with wax. Dewaxed shellac is a clearer, and is also somewhat more moisture resistant than shellac with wax.
I think the three year life span is a bit optimistic for most uses, as I suspect it assumes ideal conditions at all stages of the supply chain. Toward the end of the life span the shellac is likely to dry softer. The heavier cut shellacs, are not as heavily processed to add to longevity, but being a heavier cut makes them deteriorate less rapidly.
Why mix from flakes? You only need to mix what you will use in a short period, so you know it is fresh. Flakes are available in a considerably wider range of shades and colors, so that, for example, it is possible to obtain a dark shellac that is dewaxed. Flakes themselves, when kept in cool dry places have a very long shelf life. IN the US, there is VERY little premixed shellac not manufactured by Zinnser--NO significant manufacturers except Zinsser. Homesteadfinishing does pre-mix some shellac I believe, and Liberon has some shellac products available in relatively limited distribution. These are not likely to have the special processing needed to add longevity to the liquid shellac, since Zinsser has patented some processes.
When you apply shellac each new "coat" melts, at least partially, into the coats below it, so that effectively you have only one coat of shellac, whether you have applied in a few heavy cuts or many light cuts. Thats why sanding between coats isn't needed with shellac, other than occassionally to remove defects.
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