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Problem sealing sunburst with shellac http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=38578	Page 1 of 1

Author:	Ron Belanger [ Mon Dec 17, 2012 12:07 pm ]
Post subject:	Problem sealing sunburst with shellac
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.

Author:	Ron Belanger [ Mon Dec 17, 2012 12:09 pm ]
Post subject:	Re: Problem sealing sunburst with shellac
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. If anyone else is using SV. OK to apply directly over the shellac, or perhaps apply a seal coat of the epoxy as well?

Author:	B. Howard [ Mon Dec 17, 2012 1:02 pm ]
Post subject:	Re: Problem sealing sunburst with shellac
This is different than working with stains on bare wood. To place the burst toner between seal coats like this you must use a binder in your toners. Typically this would be the same material as your finishes, in this case shellac. The problem is not really atomization, it's the fact the the stain is just laying on top of the sealer and reactivating when the solvents hit it. It must be tied into the finish at this point. Add your toner direct to shellac, keep it under %15.

Author:	Ron Belanger [ Mon Dec 17, 2012 5:08 pm ]
Post subject:	Re: Problem sealing sunburst with shellac
Thanks Brian, I am partway through testing the following and it seems to be working. Since I have a lot of color in the wood already and I really like the way it pops the grain, I am reshooting the burst on the bare wood with the dye and then sealing it with shellac. This part worked fine so far. Tomorrow, if there are any uneven color areas, I will then use the color in the shellac and smooth them out. Then I will shoot the KTM SV Fingers crossed. I had a bad experience shooting waterborne on bare wood. It really potato chipped and took weeks to level out again, almost.

Author:	SteveSmith [ Tue Dec 18, 2012 6:27 am ]
Post subject:	Re: Problem sealing sunburst with shellac
Definitely not a good idea to shoot waterborne finishes on bare wood. Must use a sealer; I prefer 2 coats of shellac.

Author:	dunwell [ Tue Dec 18, 2012 4:35 pm ]
Post subject:	Re: Problem sealing sunburst with shellac
A couple suggestions, non standard but worked for me with mandolins. - Shoot shellac or other desired stuff to the raw wood to pop the grain. - top with vinyl sealer. This separates the undercoats with a finish with different solvent - shoot my color coats in very thin shellac. I use transtints, same as the stewmac stuff. Make these coats pretty dry so they don't run. If you gorff the color coats you can just wipe them off with alcohol w/o damaging the under coats or having to go back to wood. - top with one light coat of vinyl sealer - follow with some sprayed build coats of shellac - FP for finish coats. Makes a very thin finish, under 5-thou. Just some thoughts, Alan D.

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