More Finishing

[rrich]

I made a box for use in the shop from some oak veneer plywood. Then I finished it with post application cut shellac. (Zinzer Bull's eye amber) Several people have commented how good the finish looks. I'm inclined to agree and was thinking about using shellac on a computer desk.

As a computer desk, the finish needs to be more than shellac. So I'm thinking about using a water based polyurethane (Oil is almost impossible to get these days in California.) over the shellac.

Is it necessary to dewax the shellac?
How can one tell if the shellac was or was not dewaxed?
How can one tell if after application, a shellac was dewaxed? (Does it feel waxie?)
What is the process for dewaxing shellac?
Does the wax prevent the polyurethane from adhering to the shellac?

Thanks,

[rrich]

I guess I should explain.

Straight from the can, brushed on in a very heavy coat.

Cover the flat surface. The shellac actually penetrates the wood.

Wet a rag with denatured alcohol and wipe the surface immediately after applying the shellac. (Maybe two passes with the rag.)

The results are a nice and even amber tone. In 20 minutes the shellac finish is dry enough to handle.

[TDHofstetter]

Pretty much... if the labeling doesn't indicate that it's dewaxed, it's probably not. There IS shellac on the market that's wax-free - for example (if you like the premixed, canned stuff) there's Zinsser BullsEye SealCoat:

http://www.woodcraft.com/product.asp...&FamilyID=4758

If you're more inclined to buy flake & mix your own to your own specs, Hock makes fully dewaxed flake in three different grades:

http://www.woodcraft.com/family.aspx?familyid=2024

I tried to find dewaxed shellac on Rockler's site, but alas there's none to be had there.

EDIT: Yep, undewaxed shellac does interfere with polyurethane overcoats. I dunno any good way to tell, after the fact, whether shellac's dewaxed or not, short of experimenting with polyurethane over it.

TO DEWAX SHELLAC... dang. It's only a guess, but I'd bet it has something to do with a lot of heat and a heavy flooding with mineral spirits or another solvent that'll dissolve wax.

-- Tim --

Member of the
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[Sawduster]

The normal process for dewaxing shellac is to simply let the container (clear glass is good so you can see inside) sit for a couple days. The wax will settle out to the bottom and you just decant the clear liquid off of the top into another container.

That is the normal process. Can't do that with the regular Zinnser stuff, the 3# cut available in amber and blonde at the box stores because it has a bunch of other stuff in it to increase its shelf life. I tried and after a week of sitting in a glass mayonaise jar I had maybe 3/4" of clear stuff on top and the rest of the nearly full jar was some ugly yellowish crap.

Like Tim said, though, the Zinnser Sealcoat is dewaxed shellac, a 2# cut. Problem is it sounds like you want the added color from the amber shellac and since you're wanting to use a water based clear poly on top of the shellac, you definitely need dewaxed. For that I'm thinking you'll need to buy amber flakes or "button-lac" and mix up your own. May have to dewax it after you mix it depending on whether you can get dewaxed amber flakes.

[dbriski]

You can get the Seal-Coat lots of places, Big Box, Rockler, Woodcraft. One option is to apply a couple coats of your amber to get the color, then apply one coat (as long as you get full coverage, maybe 2 coats) of the seal coat and then apply the poly on top.

[rrich]

I think that I'go with Tim's suggestion and try the dewaxed flake method. It seems too simple to screw up.

[Sawduster]

I've applied oil based poly over the regular Zinnser stuff and never had an issue with it. Just figured the solvent in the poly dissolved and handled what ever wax might interfere with adhesion. But I've since heard from a couple of the experts that it is nearly impossible to remove the wax once the shellac has been applied to a surface. I don't know what the results would be if a coat or three of dewaxed shellac like Sealcoat was added over previously applied shellac that contained wax.

But if one can get dewaxed orange and garnet shellac flakes, then it would be the way to go if he wanted to get the tinting.

[Cody Colston]

Rich,

Your Bullseye shellac is not dewaxed. Only the Zinsser Seal Coat is dewaxed.

If you put water borne finish over the waxed shellac, it will crinkle...DAMHIKT. It's a great finish if you are going for an antique look...like the Sistine Chapel. ;)

I bought a gallon of the Zinsser Bulls-eye Shellac and the wax all settled to the bottom. I just poured off enough of the clear Shellac for the job I was doing and left the wax in the bucket with the rest.

Cody
Tyler, TX

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