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Timbuck
02-27-2016, 03:56 AM
I've been bending some Koa and I'm having trouble with green stains coming out of the wood after spritzing with water and i'm looking for ways of prevention and cure ..I've read that bending between brown paper to stop it contacting the metal will work ..and 3% Hydrogen Peroxide solution will remove staining, also white vinegar or baking soda.
any advice is welcome as I dont work with Koa very often.

Beau Hannam Ukuleles
02-27-2016, 04:50 AM
I use butchers paper for Tassy blackwood (same as koa).

resoman
02-27-2016, 06:41 AM
I wonder if it could be something in the water. Have you tried distilled water? I use a kind of "kraft" paper I get from the hardware. It's kind of like brown paper bag paper but thinner and in a roll

Allen
02-27-2016, 10:03 AM
I use brown paper like the stuff that StewMac stuffs their parcel boxes with. Actually it's exactly like that as I save it for just this job. Works a treat.

Pete Howlett
02-27-2016, 10:45 AM
Ken - I gave up mechanical bending for this very reason. I found no way of getting rid of this and with your set-up, bending dry between kraft paper is so risky. Distilled water, de-ionised water, rain water - none of it worked and since spring-back is a major issue for me I went back to my iron to preliminary bend then resort to the heat blanket to set it. Sorry beau - Tasi Blackwood is nothing like koa - I am always unclear why the comparison. Even before you start to bend and have to work it, it's presenting problems. My sawyer says it's a PITA to convert and I concur. I also think it's sonically inferior to it's comparison koa... Now I'll have all the antipodeans barking for blood :) :)

sequoia
02-27-2016, 04:59 PM
I heard somewhere that metals used in making stainless steel can cause a green staining on wood. Something to do with the high chromium content. The cure was using non-stainless steel. I use aluminum wraps so never had that problem.. Also using deionized water is a good idea. Less salts the better. Who knows what is in your tap water over there in Wales.

Pete Howlett
02-27-2016, 09:40 PM
It's the minerals in the koa that's the issue.

DotBot
02-27-2016, 11:08 PM
To remove the stain you can use a solution of oxalyic acid, which is commonly sold as deck cleaning fluid. A good scrubbing with this, followed by a rinse with plain water, will do the trick.

I'll add that, indeed, my experience is with Tassie blackwood, not koa, but this approach has worked for me consistently.

Cheers,
Aaron

Kekani
02-28-2016, 06:11 AM
No issues with staining bending on a blanket.

I've always considered getting a set of slats to sandwich the sides, but never have, so its been straight on the blanket from almost day one.

Check out Taylor's Factory Fridays (?) - they show bending wrapped in paper; dry. Neat stuff.

Edit: Here's part one that shows the machines, wrapping process and waist bending

https://m.youtube.com/watch?v=jxEqGqi4D-E

If you want to go on. . .
part 2 bout bending

https://m.youtube.com/watch?v=I1XZwLA5PiM
part 3 overbending (time to make one of those overbent holding molds)

https://m.youtube.com/watch?v=UxFINvii-KQ
and 4
https://m.youtube.com/watch?v=ybYdRtthNOs

Doug W
02-28-2016, 06:11 PM
My only experience in bending ukulele sides is whatever kind of pine from "Home Depot" my 2x4 is. I tried using city water to soak the sides and then distilled water. Both resulted in blue stains on the wood.