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Sunburst with shellac
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=55396		 Page 1 of 2
Author:  bcombs510 [ Sat Dec 10, 2022 10:50 pm ]
Post subject:  Sunburst with shellac
Hi folks,

I’m following along with Jeff Jewitt’s course on doing a sunburst. I have three “test tops” which I’ve already sealed with a coat of isolante.

I plan to use shellac to spray the colors on following the mix ratios and setup described in the course.

What I cannot quite understand is how the shellac won’t be affected when the topcoats are applied? The finish is UV cured polyurethane which is high solid but still solventborne. Won’t this just wreck the shellac and the dye?

I could spray a second sealer coat over the burst before putting the topcoats but the sealer is solventborne as well.

Maybe this is not a concern at all? Jeff’s course shows using either shellac or lacquer to spray the burst and then spray lacquer coats as top coat. So maybe the shellac will be fine?

A second question is how long should I let the shellac cure before putting topcoats down? The finish I use is UV cured so it’s going to cure instantly but will have the shellac between the topcoat and sealer and will be continuing to harden? Is that a lean over fat violation?

Thoughts are appreciated, maybe it’s gonna be alright? :)

Brad


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Author:  Clay S. [ Sat Dec 10, 2022 11:50 pm ]
Post subject:  Re: Sunburst with shellac
To apply the first few coats of clear over a burst I apply light coats and if I am only bursting the top I will spray it flat. That will minimize the possibility of the solvents dissolving the color coats and causing them to run. After you have locked in the color coats spraying full wet coats should not be a problem.
Author:  SteveSmith [ Sun Dec 11, 2022 5:27 am ]
Post subject:  Re: Sunburst with shellac
I often spray color tone in shellac to darken necks before I French polish. After the color is on I spray a few coats of clear to lock it in before I proceed. I spray light coats and even though it flashes off quickly I like to only do two or at most, three coats over the course of a day before I let it dry overnight.
Author:  doncaparker [ Sun Dec 11, 2022 8:33 am ]
Post subject:  Re: Sunburst with shellac
I plan to be a third party beneficiary of this discussion. Thanks for the info!
Author:  bcombs510 [ Sun Dec 11, 2022 12:20 pm ]
Post subject:  Re: Sunburst with shellac
Here are the three amigos. These are Martin reject tops that had areas of staining that needed sanded out and as a result those areas are too thin.

I glued a paint stick on them to hang in the spray booth. I’ll get three (or more) shots at a burst before taking it to an instrument. I’ve already put down a seal coat on these. I’ll practice taping off the rosette and doing two different kinds of burst as shown in the Jewitt course.

Wish me luck!

Image


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Author:  RusRob [ Sun Dec 11, 2022 12:56 pm ]
Post subject:  Re: Sunburst with shellac
Brad,

I have never done a burst in shellac but I am guessing it is no different that using lacquer. I have done a number of bursts in lacquer so I am familiar with what you are doing.

I do my burst by first sealing the top with a couple of coats of sealer. You will want to level the finish prior to applying any color. If the surface isn't perfect it will show up so make sure your top is prepped properly. (But I am sure you know that)

After the seal coat is dry (I would give it at least 24 hours) I start spraying out the colors. I do my burst similar to how Gibson does (or did) theirs. I lay a medium clear coat over each color, I do this in case I have an issue or mistake I am able to wet sand each color off separately. I also put a couple of clear coats over the final burst. Since I use lacquer I will allow it to dry for a couple of days before level sanding and putting the final clear coats on.


Since you are planning to use shellac for the burst colors and a UV cured polyurethane I would give the shellac plenty of time to cure. The last thing you want to do is trap solvents under a finish that won't let it breath. I think I personally would let it sit for a couple of weeks before clearing.

As for messing up your burst with the clear, it won't effect it as long as you spray at least 1 coat of shellac over the colors.


Here is a link to a Gibson CF100 that I restored and replaced the top. Toward the end of the thread Is how I do my burst and why it is important to lay clear down before and during the spraying process.

https://luthiersforum.com/forum/viewtopic.php?f=10137&t=46629

Hope this helps,
Cheers,
Bob
Author:  bcombs510 [ Sun Dec 11, 2022 1:26 pm ]
Post subject:  Re: Sunburst with shellac
Fantastic advice. Thanks, Bob!

I had it drilled in my head from the Tom Bills French polish course about waiting 3 weeks for final hardening of the shellac.

I’ll need to think about this aspect long term because the point, for me, of the UV finish is the speed. Waiting weeks on shellac to harden is not ideal. I may consider bare wood burst as a long term plan. There is already sealer on the test tops but maybe after a test run I’ll sand one of them back and try bare wood to see how it looks.


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Author:  Michaeldc [ Sun Dec 11, 2022 1:28 pm ]
Post subject:  Re: Sunburst with shellac
Hi Brad,

I did these two guitars following Jeff’s recipe using shellac and EM6k. Folks spray nitro over shellac all the time. I can’t imagine the solvents in the UV cure stuff to be any hotter than lacquer thinner.

Oh, and when Jeff says “do not to try to touch it up”, don’t try to touch it up….

Best, M

PS I think I waited 24hrs before top coats..
Author:  bcombs510 [ Sun Dec 11, 2022 2:38 pm ]
Post subject:  Re: Sunburst with shellac
Thanks for the feedback, Michael.

And both of those…. Aye chihuahua! :D


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Author:  RusRob [ Sun Dec 11, 2022 3:08 pm ]
Post subject:  Re: Sunburst with shellac
bcombs510 wrote:
I’ll need to think about this aspect long term because the point, for me, of the UV finish is the speed. Waiting weeks on shellac to harden is not ideal. I may consider bare wood burst as a long term plan.


If you are looking for speed then why not use a UV cured filler (such was discussed in another thread just recently). I am guessing you can tint the UV cure finish to do your burst.

That way you should be able to blaze through the finishing process and not have to wait for cure times.

I personally love the finishing process, but then I don't mind the smell of lacquer. I have been looking for other alternatives to spraying lacquer but have not found anything that is as easy or as fool proof (at lest for me).

Cheers,
Bob
Author:  bcombs510 [ Sun Dec 11, 2022 3:13 pm ]
Post subject:  Re: Sunburst with shellac
Do you mean UV cured porefill? I do use that, yes.

It’s a good point about tinting the topcoat. UV cured polyurethane is 80-90% solids so you don’t put a lot of coats. I suspect I would have to have the coloring super dialed in to achieve that. It’s an idea though! Maybe thinned coats to start and then last two coats full. I only do 4 coats total putting down 8 wet mils.


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Author:  bcombs510 [ Fri Dec 16, 2022 6:20 pm ]
Post subject:  Re: Sunburst with shellac
Here are some pics. Jeff’s course he talks about three stages. I’ll try to describe them. Everything is sprayed with a HVLP with 1mm fluid tip. The base of the spray material is super blonde shellac with everclear and the dyes are mixed into that base. The final top coat is just shellac. Any feedback on improving is appreciated. I have a few more cracks at it with the test tops. :)

- Start with sealed wood (Isolante sealer)

Image

- Toning - where you spray the full top with a little extra focus on the center. This is done with the amber center color.

Image

- Shading - starts with the middle color which is reddish brown. Shading in from the edges and feathering into the amber center color.

Image

- Shading - putting the darkest color on feathering into the previous. This is a mix of black and dark brown.

Image

- Unifying - this coat is done with the first amber color and is supposed to unify the three previous coats.

Image

- Topcoat - Two coats of super blonde shellac sprayed with the top laying horizontal to prevent runs.

Image

Any questions please let me know.

Brad


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Author:  doncaparker [ Fri Dec 16, 2022 6:40 pm ]
Post subject:  Re: Sunburst with shellac
It looks great to me, Brad! I would be proud of that work. So, you'll wait 3 weeks for the shellac to fully shed all the alcohol, then apply the UV cure topcoat?
Author:  bcombs510 [ Fri Dec 16, 2022 6:48 pm ]
Post subject:  Re: Sunburst with shellac
Thanks, Don. The plan right now is I’m going to do two more tests with the test tops and then see if I can convince myself to spray the curly walnut 00 I’m working on. I hope I can convince myself to do it because I think that thing would look fabulous with a burst.

Based on Michaels feedback I will probably wait just a week before putting a topcoat on the real deal. I don’t plan to spray a topcoat on the test dummies.


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Author:  James Orr [ Fri Dec 16, 2022 7:47 pm ]
Post subject:  Re: Sunburst with shellac
bcombs510 wrote:
I hope I can convince myself to do it...


I think you can convince yourself to do it. That looks fantastic.
Author:  guitarjtb [ Sat Dec 17, 2022 7:18 am ]
Post subject:  Re: Sunburst with shellac
Brad, nice looking burst on your test top. Which red did you for mixing the reddish brown color? 5038 or 5032?
Author:  SteveSmith [ Sat Dec 17, 2022 7:22 am ]
Post subject:  Re: Sunburst with shellac
That looks good Brad. I’d be happy with that one on a finished instrument.


Steve
Author:  kfish [ Sat Dec 17, 2022 9:47 am ]
Post subject:  Re: Sunburst with shellac
Nice job Brad. I like that the changes in shade are so blended rather than a defined shape.
You don't have to worry about binding on your test tops but did you mask the rosette and scrape it? To me, clean up of the bindings and rosette is one of the biggest challenges on a burst. Would like to see what you do with that on your 00.
Kent
Author:  bcombs510 [ Sat Dec 17, 2022 1:58 pm ]
Post subject:  Re: Sunburst with shellac
guitarjtb wrote:
Brad, nice looking burst on your test top. Which red did you for mixing the reddish brown color? 5038 or 5032?

Thanks. It’s #5032.


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Author:  guitarjtb [ Sat Dec 17, 2022 2:37 pm ]
Post subject:  Re: Sunburst with shellac
bcombs510 wrote:
guitarjtb wrote:
Brad, nice looking burst on your test top. Which red did you for mixing the reddish brown color? 5038 or 5032?

Thanks. It’s #5032.


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Thanks
Author:  Clay S. [ Sat Dec 17, 2022 3:07 pm ]
Post subject:  Re: Sunburst with shellac
Hi Brad,
Nice looking burst!
Being a "belt and suspenders" guy, I would topcoat at least one of the test tops to see how it looks with the dye and shellac. Probably not necessary, but I would do it anyway.
Author:  bcombs510 [ Sat Dec 17, 2022 4:25 pm ]
Post subject:  Sunburst with shellac
That’s a good idea, Clay. I will do that.

Kfish, for the first test I did just a quick mask off. I did another test today and took the time to mask off the rosette more carefully. This rosette is much more complicated than mine so I think it shouldn’t be an issue to get a clean result. See the last video for some ASMR footage of peeling off masking tape. :D

Here are pics of what Jeff calls the “Iced Tea” burst. The “Buckeye Burst” and the “Iced Tea” are quite different recipes.

I also put some videos below of the spray process, any feedback I should consider please share it. :)

Pics:

Image


Image

Image

Image

Image

Image

Image

Image

Image

Videos:

https://youtu.be/2_I4_GYZ7V4

https://youtu.be/f0wU5-mLkQ8

https://youtu.be/o_KLnN-hk5k

https://youtu.be/pJQw5SDKI1Q

https://youtu.be/vZr7xQJos2w

Brad


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Author:  kfish [ Sat Dec 17, 2022 9:56 pm ]
Post subject:  Re: Sunburst with shellac
Nice job Brad. Did you have to scrape the rosette at all? Thanks for documenting this process/
Kent
Author:  bcombs510 [ Sat Dec 17, 2022 10:04 pm ]
Post subject:  Re: Sunburst with shellac
kfish wrote:
Nice job Brad. Did you have to scrape the rosette at all? Thanks for documenting this process/
Kent

No scraping needed,I just masked it off.


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Author:  ballbanjos [ Sun Dec 18, 2022 7:59 pm ]
Post subject:  Re: Sunburst with shellac
Dang but a nice sunburst looks good. Good job Brad!

Dave
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