E6000 Over Shellac with Bad Results

[Steve Kohn]

I just completed finishing a headboard and 2 nightstands. They were a combination of walnut and ambroysia maple.

I sprayed, using a Fuji Q4 Pro HVLP system, 2 coats of Bulls Eye wax free shellac last Saturday, followed by 4 coats of Target's EM6000 on Sunday. I have let the finishes cure for a week and was rubbing them out today.

I rubbed down the shellac with a new nylon abrasive pad, tack ragged, and then overcoated with the EM6000. All were newly opened cans or packages.

I have a significant amount of crazing in the finish.

What did I do wrong?

[Steve Schoene]

Look at the date on the Seal Coat can. Target has reported problems with finishes over SealCoat that isn't very fresh--like within 6 months of it's manufacturing date. (Shellac freshness doesn't depend on when the can is opened--never opened cans can be over the hill.) It is Seal Coat that you used, I assume, since that's the only Zinsser brand that's dewaxed shellac except for the aerosol.

[Conrad Fiore]

Steve & Steve,
I believe the issue with the SealCoat is not the freshness, but the amount used. There are no issues with Dewaxed from flake but if the layer of SealCoat is too heavy, crazing can occur under the 6000. Steve, I would also suggest that tack rags not be used under the Target finishes, unless they are specifically made for WB finishes. Target recommends that you wipe with a rag that has been dampened with a 50/50 mix of water/DNA.

[Steve Kohn]

Good advice from both of you. Now that you mention the issue of tackrags under WB finish I remember reading about that.

I had not heard about the "old" shellac issue. I'll check the date code.

Thanks to both of you.

[Scott Holmes]

I too suspect; either too much shellac, or the tack rags, probably both.

Shellac to seal the wood, not build it up.

[Neal Clayton]

if the shellac was old i think you would have noticed. it struggles to dry when it's too old. if you managed to buff it and tack it without noticing any issues the shellac was probably fine.

[Steve Kohn]

The shellac dried fine. Apparently the tack rags or too heavy an application is the culprit.

[Jim Becker]

I never use tack rags...after spraying two light coats of Sealcoat, I "lightly touch" it with 400 paper to remove any nibs (no real sanding) and then just wipe it down with a lint-free cloth, being sure to rotate the surfaces of the cloth to avoid putting any dust back on the surface. Then I spray 2-3 coats of EM6000. (I did that today for my latest tack trunk commission)

But as already pointed out, too much shellac is to be avoided, especially as a barrier coat. The only reason I spray two coats is to insure complete coverage...they are light coats and I move the gun left-right for one coat and up-down for the other to make sure there is even finish everywhere.