Finishing Koa wood

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eclipsme

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I recently finished building 2 long neck sopranos with koa bodies. I had never worked with koa before, but the wood has some great grain, etc, but I am disappointed by the finish. It seems a bit flat, not enough contrast, dull. Photographs well but not so much in person. Nice, but with no 'pop'.

I finished without stain using water based polyurethane.

My hunch is that others are using a stain to bring out the grain.

How do you finish koa? Do you use stain? Which one?

Thanks.
 
The waterbase finish is the problem. It won't bring out the grain or colors. I don't use water base, but I have played with it as a safer finish for students. You can use shellac under the water base and get good results.-Bob/Pegasus Guitars & Ukuleles
 
Which water based poly finish did you use? There are good water based finishes that can pop grain as well as anything, and then there are bad water based finishes!

Can you share some photos? What exactly is the problem - I know you said it doesn't look good and seemed flat, but can you be more specific? How did it look when unfinished?

How did you prepare the wood - if sanding, to what grit?

Finish work can be real simple but also maddeningly complex - for me at least, it's hard to know what advice to give without a lot of details.
 
Which waterebase finishes have you used that pop the grain as good as solvent based ones? That could be interesting for students and beginners.
 
Pegasus Guitars said:
Which waterebase finishes have you used that pop the grain as good as solvent based ones? That could be interesting for students and beginners.
Click to expand...

Good question. It seems that many (most?) water-base finishes are clear, while most solvent-base finishes are amber to some degree. I would guess that's what is lacking from whatever the OP used. I suppose one could use a coat or two of water-base stain first.
 
I use a single coat of high quality amber shellac (2 lb cut) as a base coat and that pops the grain really well and acts as a "stain". Compatible with all water based finishes.
 
Danish Oil ( Liberon ) finish with Tamiya sand paper.

More info on my blog and on my YouTube channel :



5UgpdCvJxAnS4dxGg-3-Ajv6sBA.jpg
 
Last edited:
Some years ago I had easy access to ready made shellac and used it as a sealer coat before finishing with water based poly on mahogany, walnut, cherry, etc. to good effect, accentuating the grain. When the supplier stopped carrying it, I stopped using it. Silly me!

I assume those using it are purchasing flakes??? I did look at this at one point but got confused which were dewaxed and which not. What brands are you using? Time for me to cut my own!
Thanks for all the replies.
 
eclipsme said:
I assume those using it are purchasing flakes??? I did look at this at one point but got confused which were dewaxed and which not. What brands are you using? Time for me to cut my own! Thanks for all the replies.
Click to expand...

I get my shellac flakes from LMI (Luthiers Mercantile International)*. It is high quality stuff and is dewaxed which is what you want. I use two types: the ultra pure blond which is as light as you can get for not darkening the wood too much. Or the dark amber for using on light woods to give it a "vintage" look.

Getting the stuff into solution is a bit of a pain but worth it. Here is how I do it: A 1 "pound" cut of shellac is 1 pound of shellac to 1 gallon of alcohol. Since this is obviously too much, you do a smaller ratio like adding 2 oz. of flakes to 8 oz. of alcohol producing a half-pint of 2-lb.-cut shellac. Keep shaking it and shaking it which can take hours until most of the shellac goes into solution. Then I filter it through coffee filters into a jar and label it with the date as shellac has a relatively short life and you want to use fresh shellac at all costs.

shellac-mediumdark-blonde-8-oz-dewaxed.jpg

* https://www.lmii.com/finishes/3090-shellac-mediumdark-blonde-8-oz-dewaxed.html
 
I get my shellac from The Shellac Shack in Oregon. Nice folks. Will send you the instructions for various # cuts with your order. Fast service and the shellac always disolves easily. Bob/Pegasus Guitars & Ukuleles
 
I use LMI's shellac flakes as well. For one thing, it's convenient to just tack it on to an order when I need it. Once in a while if I need some immediately, I go for the zinsser seal coat dewaxed shellac. Seems like the best stuff in terms of premix. I just throw it out once it stops sanding easy, maybe 6 or 8 months...

In terms of water based finishes - I've had the best luck with Varathane Ultimate water based poly. Much better results than any other water based poly I've tried. It's widely available, easy to apply, dries fast and hard, can be buffed easy, and does a good job of popping figured wood. If I literally want to pop the grain (versus the figure, if that makes sense) then I either tint the finish or apply amber shellac first.
 
dwizum said:
I use LMI's shellac flakes as well. For one thing, it's convenient to just tack it on to an order when I need it. Once in a while if I need some immediately, I go for the zinsser seal coat dewaxed shellac. Seems like the best stuff in terms of premix. I just throw it out once it stops sanding easy, maybe 6 or 8 months....
Click to expand...

Thanks all for pointing me to suppliers. Also, I looked at the Zinseer products earlier but for some reason couldn't figure out if it was dewaxed. Of course, my first search turned up the answer just now!

I shall be returning to a shellac first coat again, but will experiment with the different colors.

Thanks again!
 
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