Spraying shellac. Tips and tricks would be appreciated - created 12-13-2008

Eliasson, Anders - 12/13/2008.05:15:02

Hi.

I have read what I could find in the library on the subject. The info is some years old.

I´m thinking of spraying with a small 0,8mm hvlp touch up gun. I would like to make base and body coats and finish of either with French polish or with KTM9 waterbase lacquer.

Questions.

How thick a coat do you spray?

Intervals between coats?

curing time before handling?

Has anyone levelled and buffed sprayed shellack?

Has anyone sprayed KTM9 over a shellack base?

I think thats enough questions for now. I´m looking forward to your answers.

Saludos

Anders

Hamlett, John - 12/13/2008.12:31:30

I've sprayed sealer coats and top coats of shellac. I try to spray thin coats, I'm not able to "hang" as heavy a coat of shellac as I can lacquer. It's similar to lacquer, just wait a minute or so to re-coat. You can handle it in minutes, but it continues to harden for a while so be careful with it.

Shellac can be leveled and buffed easily. In fact, I'd recommend hand buffing because power buffing can be too aggressive for shellac and you can "burn" through quickly unless you're skilled and experienced with it.

As for KTM9 over shellac, I have no experience with that, but I'm sure it's been tried and someone will fill us in on whether or not it works.

Eliasson, Anders - 12/14/2008.12:18:21

Hi John

Thanks for your answer.

One thing I would like you to explain:

You write,

just wait a minute or so to re-coat. You can handle it in minutes, but it continues to harden for a while so be careful with it.

Does it mean that you do multiple coats in short time and thats it, or do you do various sessions of multiple coats?

Anders

Hamlett, John - 12/14/2008.14:20:00

For a sealer I usually spray two light coats, the second just minutes after the first. One reason is; I build mandolins with sunbursts done with alcohol soluble dyes. A coat of shellac that is the least bit too heavy can bleed and smudge the dyes, so the first coat is just a mist coat to lock down the dyes. The second coat can be a little heavier and actually does most of the sealing. I scrape the bindings after the shellac sealer so I don't want it thick enough to chip at the scraped edge.

Whatever finish I'm using then goes over the shellac sealer. I've never done build coats with sprayed shellac, but that could be done. It would require multiple sessions of 2 or 3 coats with sanding in between. I use lacquer or varnish for build coats. I've also sprayed a few thin coats of shellac over varnish for a buffed gloss coat. Leveling and buffing the shellac is easy, as finishes go, but "burning through" is easy also, as I mentioned earlier.

Francis, Tony - 12/14/2008.18:05:01

Hi John,

What kind of spray gun/setup are you using to shoot shellac?

Best,

Tony

Hamlett, John - 12/14/2008.20:03:19

Conventional spray gun. It's an old, obsolete Sharpe model 90 that I bought over 20 years ago to paint my Sunbeam Alpine (red). I use it for lacquer, varnish, shellac, whatever I'm spraying. It's starting to not work as well as it used to, so I think it's days a numbered around here. I'm not much for fancy spray systems, obviously, and I'll be staying with a conventional gun, but may go from siphon feed to pressure feed with a remote pressure pot.

I was once refered to as the kind of guy who can get a good finish with a Windex bottle...

Eliasson, Anders - 12/15/2008.03:18:40

Again, thanks for the answers. I´m almost ready

John wrote:

I build mandolins with sunbursts done with alcohol soluble dyes. A coat of shellac that is the least bit too heavy can bleed and smudge the dyes,

So in order to avoid prolems with bleeding from the dyes you seal with two very light coats. I can imagine that this would be same in order to avoid bleeding from rosewood bindings to sycamore purflings?

Hamlett, John - 12/15/2008.15:53:59

Similar, it can't hurt!

Sometimes rosewood color will bleed in finish solvents, alcohol might do it too.

Francis, Tony - 12/16/2008.05:08:43

I was once refered to as the kind of guy who can get a good finish with a Windex bottle...

John, I wouldnt doubt that for a single second!

Best,

Eliasson, Anders - 12/19/2008.03:08:23

Ok, a follow up.

I sprayed with a 0,8mm HVLP touch up spray gun (SATA copy) I sprayed at 35 psi.

First I did test on scratch, . With purfling and rosewood binding. then later repeated on a cypress flamenco guitar

Two very light (thinned) and very fast coats and then various sessions during the day with 3 hours inbetween. One session would be 3 coats with a few minuts in between. I did a total of 5 sessions and I did a bit of scuff sanding inbetween.

Everything looks good. A runner during the first session taught me to open the fan a bit and move a little faster. There are a few dust "things" in the finish which I hope to be able to remove.

The guitar will be left for a week and the wet sanded and hand polished.

I will post a follow up.

Anders

octigan, rod - 12/19/2008.03:45:45

Hey.. I've sprayed shellac on my mahogany and spruce arch top, it turned out pretty good but the yellow tinge doesn;t suit white timbers, does anybody have alternatives for an ultra clear finish?

Proulx, Mario - 12/19/2008.09:09:06
Hear the colors....

Super Blond?

Mills, Carl A. - 12/20/2008.20:05:56

Super Blond is the only one that dosen't have an amber tint after drying.

octigan, rod - 12/21/2008.20:19:22

Pardon my ignorance, but is super blonde a type of shellac or another product.

sysop - 12/21/2008.20:20:57
Deb Suran

It's a type of shellac.

Leirer, Bill - 12/21/2008.20:41:00

A photo of different types of shellac on different woods, and a nice article from Jeff Jewitt:

http://www.homesteadfinishing.com/htdocs/shellac3.htm

Eliasson, Anders - 01/04/2009.12:49:32

Follow up

I wet sanded the guitar with Micro mesh up to 4000 grit and Hand polished with LMI´s fine cut polish.

The result is very nice and very clean. The surprice is that the finish is harder than when I´ve French polished shellack. Any comments on that?

Leirer, Bill - 01/05/2009.18:13:57

How did you measure the hardness?

Tweedy, Chuck - 01/08/2009.15:12:25
Midnight Lutherie ... because that's when I work

Andres, I was going to comment on this a few days ago but lost track.

You likely

perceive

a harder finish because your sprayed film is probably thicker than the FP film. It is very difficult to build as much film with FP than with the gun.

Eliasson, Anders - 01/09/2009.04:12:26

I test the hardness the flamenco guitarist way. A tap on the shellack with a nail. And it doesnt make such a heavy impact as on the guitars I have French Polished. I dont think a thicker finish would change that on the contrary. But mabe its just my perception because I lke the result.

As always, Time will show.

Tweedy, Chuck - 01/09/2009.11:24:05
Midnight Lutherie ... because that's when I work

Yes, the thicker finish will have the property you describe. You are measuring the dent resistance, and the mechanical strength of the thick film will help reduce dents.

Eliasson, Anders - 01/10/2009.03:56:09

You may be right.

Anyway, I like the result