Problem sealing sunburst with shellac

[Ron Belanger]

I have a problem sealing my latest sunburst with shellac.
I use the waterborne KTM - SV and I normally seal the surface and fill the pores with System 3 epoxy. However this Irish Bouzouki build is maple with a sitka spruce top and doesn't need to be pore filled, and the epoxy, if applied directly over the sunburst will smear the colors. So I thought I could seal the burst with shellac.
Here is my process to date and some photos of the problem I am currently facing.
1. Using StewMacs Colortone dyes in alcohol (55 drops per 4 oz.) I sprayed the initial burst. I used a small detail gun. at 40psi.
2. I noticed that the color wasn't as even as I liked so after sanding back to near bare wood. I sealed with a couple of coats of shellac (1lb. cut). I used a small HVLP bargain gun to spray the shellac. Air pressure to the gun was set at 23 psi.
3. resprayed burst. looked really good. same gun as above.
4. I then used the same small HVLP gun to spray the sealer coats of shellac (1lb. cut). I am not a happy camper. The result is pictured below.

[Ron Belanger]

I am now sanding it back to even color and will reapply the burst. I am thinking that I did not have sufficient atomization and the large droplets caused the color to run. Any suggestions will be appreciated. Thanks.

[Barry Daniels]

The problem is that you applied a finish with the solvent used in the underlying stain. Can't do that. You should either change the finish or the stain. A water based dye would not be affected by the shellac. Perhaps the best solution would be to eliminate the shellac and just apply the KTM over the dye.

[David King]

Isn't Colortone also soluble in water? I'd test it under KTM-9 before proceeding. You can also try adding your color directly to the KTM and using that as the carrier but only if you can get good atomization from your gun.

Certainly MEK metal acid dyes would be better all around for this job if it's something you do regularly.

Have you read through this page? http://www.lmii.com/carttwo/thirdproduc ... sed+Finish

[Mario Proulx]

I add my colors to shellac, and then shoot whatever topcoats over that. If the KTM can go over shellac, that's what I'd do.

[Mark Swanson]

Yes, far better to mix the color into the finish, rather than put it on by itself and then topcoat it.

[Ron Belanger]

Thanks for the suggestions. I love this place.
Since I already have a lot of color in the wood, and I like the way it pops the grain. I will re shoot the burst on the bare wood, then seal it with shellac. Then I will use the color in the shellac to even out the burst. Should be able to shoot the SV right after the shellac.
I am part way through a test piece now. Should know tomorrow how it turns out.
The reason I want to seal it and not shoot the KTM SV directly on the bare wood is that the last time i did that the wood really curled up, and warped from the moisture and took weeks to get back to its proper shape, almost.

[John Sonksen]

I used lacquer thinner and about 10% lacquer along with my colors to do my burst, then I found it very helpful to do my first coat of lacquer as a fog coat rather than a wet coat. Once the fog coat was done, (set up your gun so it's atomized nice but the volume is low) I was able to do some wet coats over the top without worrying about it pooling the stain.

[Ron Belanger]

Unfortunately lacquer isn't an option for me. But the shellac seems to be working fine.

[John Sonksen]

Sorry, I was giving an example of how to use compatible thinners and finishes between the burst and topcoats. Should have been more clear. Glad you got it figured out!