Question
I'm finishing some birch cabinets and have been testing how Amber Shellac works. I'm using the Zinnser bullseye stuff which is not de-waxed as far as I know. I really like the look of it but need advice on the finishing schedule.
Can I use it over water based polyacrylic? I tested that and it looks great but not sure if it's compatible. Should I put a clear topcoat over the shellac? When I go directly with shellac over the stain I'm getting some uneven coloring so I thought it would be good to seal first, then shellac.
Also, I don't have a sprayer. Any advice on thinning it so it doesn't dry so fast? How much will that detract from the color? I'm willing to get a sprayer if it would be worth it.
Forum Responses
(Finishing Forum)
From contributor C:
Zinnsers bullseye shellac is orange shellac that contains around 6 % wax - it is not intended to be used with WB or solvent base coatings. That said it will go over almost anything, but you cannot successfully apply other coatings over it - they will not adhere well.
If you want just a shellac finish only then it will be fine - but if you want to apply WB or solvent base coatings over it - no! Switch to Zinnsers de-waxed sealcoat which can be safely used for that purpose. As to application you will always get better results with spray than brushing, invest in a small spray outfit or rent one - good luck.
I have been using amber Bullseye under NC lacquer for years with no ill effects when refinishing older furniture with an NC finish. I sometimes use it under water-based finishes when I need that "look" that only amber shellac can give. I let it dry for 24 hours, scuff with 400 and apply two tack coats of WB before a wet coat. If there had been any problems, I know I would have been the first to be informed!
Bullseye shellac does contain wax. Their "Sealcoat" and the aerosol (spray can) shellacs do not contain wax. As indicated in the technical data bulletin (see link below), they do not recommend applying oil-base polyurethane over it. Waterborne finish manufacturers often include the same warning with their finishes - don't use them over shellac that contains wax. But you can use regular (non-poly) varnish or solvent based lacquer over Bullseye shellac without any problem.
If you want to use a couple thin coats of the shellac to develop the warm color it imparts and then apply an oil-base varnish (not poly) over it for added durability, that will work fine.
What kind of stain are you using? Is it a dye? If the alcohol in the shellac is dissolving the stain (dye?), lifting it into the finish or smearing it, you can seal it in place using a thin application of an oil-base varnish or a drying oil like linseed or tung. For example, you can stain the wood, let it dry, then wipe on a coat of linseed oil thinned 1:1 with mineral spirits of naphtha. Wipe off all the excess oil and let it dry for a day. Then apply the shellac. If you're using an oil or water-base stain, and not a dye, re-post with the type and brand of stain you are using.
Thinning the shellac before application won't affect the color. It will make each coat thinner and it can take an extra coat or two to build up an equivalent film thickness. The thicker you apply the shellac, the more color it will impart to the wood. Since it's a brittle finish, you want to avoid building it up too thickly. That leads to cracking and crazing as it ages. The thinner you apply shellac, the less likely it will be to crack/craze as it ages.
How are you applying the shellac now?
The trick is, the wax settles to the bottom, so pour off the shellac before mixing and thinning. Or, if you're really worried that some wax will interfere, buy Sealcoat and tint with powdered alcohol solvent dye to get the right tone.
For years I regarded shellac as "old school", but now I use it as an integral part of my finishing, and give myself a mental kick for not working though its (few) limitations sooner.
