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View Full Version : Even waterbase sunburst on spruce?



Mike Black
Nov-16-2008, 10:25pm
So what's the trick to get an even sunburst on spruce using waterbased aniline dyes? Do you seal the spruce first with diluted shellac? Airbrush? The airbrush that Stew-Mac sells states that it's not recommended for waterbased finishes. I have no problems rubbing a nice sunburst on maple, but the spruce is so inconsistent, especially in the recurve. Should I even be using this stuff on the top?

Thanks in advance!

sunburst
Nov-16-2008, 11:44pm
As evidenced by my "handle" on here, I've done quite a few sunbursts in my time. Spruce is not easy, maple is much easier.
As for water soluble anilines, I've never used them, only alcohol soluble. I have tried various types of stains (dyes, actually); anilines, metal complex, alcohol soluble, MEK soluble, and I can say that some types and some brands are much easier to work with than others.

The easiest way to get even color on spruce is to spray the dyes, and the Stewmac airbrush will probably spray the water soluble dye OK, but it might have some parts that are susceptible to corrosion from the water or something like that, hence the warning.

Rubbing the dyes generally works best with rather dilute dye mixtures and a lot of rubbing. Avoid the places that are taking too much stain and concentrate on the places that are not taking the stain as well.

I've always stained the bare wood, but some folks seal the wood first. That is a way to help even out the color because the dyes are not absorbed into the wood. It is the differential absorption of the dyes into the varying grain orientation of the carved spruce that causes the unevenness of the rubbed stain, so sealing first avoids that problem. Someone else would have to speak to how to rub a 'burst over a sealer though, because I've never tried it.

Rolfe
Nov-17-2008, 6:52am
I'm with John in airbrushing dyes onto bare wood, and he is right in mentioning how spruce can be a problem while maple rarely is. I use the TransTint dyes which Stewart MacDonald repackages under their own brand. These dyes also mix well with shellac, so I do a two-stage shading process. After the initial dye/water coloring dries, I shade problem areas, such as the recurve around the edge, with a strong mixture of dye to shellac. It is still translucent, but it evens out the appearance of the areas where the dye/water color is not even. I also use the dye/shellac to obscure other problems like glue remainders or seams that are not bound. I could probably do the whole job with dye/shellac, but using dye/water as the primary color shows more grain and is, to me, more beautiful. Following the shading, I pull tape, clean up lines, and spray a couple of coats of shellac. Then I build my finish.

amowry
Nov-17-2008, 2:46pm
Hey Rolfe, it's great to have you on the forum and to get your input in these things. Incidentally, have you switched to the new Target alkyd varnish, or are you still using their previous stuff?

Rolfe
Nov-17-2008, 3:39pm
It's good to be here! After you get to a certain age, that is a very important statement. I had to stop using Target's 8100 varnish due to persistent fisheyes, some sort of contamination that I and another luthier in Maine struggled with. I even retried 8100 after a year's break with the same results. I really like 8100 and would have stayed with it, but the fisheye problem is too complicated to deal with. I had tried the new varnish a while back and had problems with adhesion (I could peel it off inlays with a fingernail), leveling, and bridging (bridging is the ability of a finish to fill in tiny gaps). What I switched to is KTM-SV, a waterborne spar varnish, and I wrote an article about using it in Guitarmaker magazine a couple of issues ago. KTM-SV is harder to use and takes longer to sand out and polish than 8100, but it works very well on mandolins. I am currently testing a new acrylic lacquer KTM has in the works---the closest I've found to nitro, but there are some problems to work out before it is marketed. It may be more a guitar finish than a mandolin finish, but we'll see how the tests go once the problems are worked out.

Big Joe
Nov-17-2008, 7:25pm
You can put it directly on the wood and it gives a more blended sunburst with edges that are not real defined. If you spray a sealer coat first you can spray or rub your burst and it will be easier to work with. It will give a more defined line between shades but that is how most production finishes are done. Both methods can work fine, but they give different results. If you wish to go straight to the spruce, I recommend using some scraps to practice on until you are happy with your technique and outcome.

amowry
Nov-18-2008, 8:51am
Thanks for the info Rolfe. It's great to have you testing all these new finishes for us! Sorry to highjack the thread...

Mike Black
Nov-18-2008, 12:13pm
No worries!! :grin: Thanks for your help John and Rolfe. I guess I'll have to invest in an airbrush sometime. I made a more concentrated formula for the recurve and other areas with a lot of silking, and that helped even things out.