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PostPosted: Tue May 01, 2018 7:45 pm 
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Brazilian Rosewood
Brazilian Rosewood

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Been a long time since I've had a problem, but today I bent up some Aussie Blackwood and it turned a lovely shade of green. I know it will sand out eventually, but I recall there may be a solution that removes the stain. Oaxic acid or something maybe?


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PostPosted: Tue May 01, 2018 9:31 pm 
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Koa
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First name: Trevor
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Oxalic acid will do the job. Over do it, blackwood will go a bronzey colour. Not unattractive, but maybe not what you want. Wash the oxalic off with dilute white vinegar, then water. Anything with a basic pH (i.e. alkaline) will turn it green or black again.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au


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PostPosted: Wed May 02, 2018 12:05 am 
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Brazilian Rosewood
Brazilian Rosewood

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Are you saying it will go a bronze color if I overdo the acid?


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PostPosted: Wed May 02, 2018 3:38 am 
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Koa
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Yes. There is more red to the colour, heading in a mahogany direction. It's not unattractive, but may not be what you had in mind. Check it out on an off-cut. Some blackwood starts out that colour anyway, but if it went green on you it probably started out more on the brown side.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au


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PostPosted: Wed May 02, 2018 7:14 am 
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Brazilian Rosewood
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I oversize my sides to possibly remove stains , anomalie,s etc with a very small sharp scraper blade as found in a stanley number 80 scraper


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PostPosted: Wed May 02, 2018 9:37 am 
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Brazilian Rosewood
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Thanks folks!

Fortunately most of it is on the inside. I reflect on the irony of how I can go dozens and dozens of guitars problem free on the budget line, but as soon as it's a show glossy with a deadline, things go squirrelly...Image

This is its color, and the color I'd like for it to stay.


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PostPosted: Wed May 02, 2018 11:33 am 
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Brazilian Rosewood
Brazilian Rosewood

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I think this is the stuff I'm after?

https://www.homedepot.ca/en/home/p.all- ... 39775.html


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PostPosted: Wed May 02, 2018 11:51 am 
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Brazilian Rosewood
Brazilian Rosewood

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Turns out you can get it in crystal form at Shoppers Drug Mart! That store gets better and better:)


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PostPosted: Wed May 02, 2018 12:18 pm 
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Brazilian Rosewood
Brazilian Rosewood

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Many paint stores carry oxalic acid. It is poisonous so use a little bit of care ( don't put it near your coffee mug).


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PostPosted: Wed May 02, 2018 5:09 pm 
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Koa
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I get it in crystal form from the hardware store, just labeled Oxalic Acid. Use "rubber" gloves.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au


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PostPosted: Wed May 02, 2018 5:19 pm 
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Brazilian Rosewood
Brazilian Rosewood

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Thanks Trevor! What is the mix ratio, and are nitrile gloves "rubber" enough?


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PostPosted: Wed May 02, 2018 10:22 pm 
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Koa
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meddlingfool wrote:
...are nitrile gloves "rubber" enough?

Anything that will keep it off your hands. Nitrile should be fine.

meddlingfool wrote:
What is the mix ratio...

The directions on my stuff say 250gm per litre. However, I use it at much lower dilutions, probably more like a tablespoon per pint, or a teaspoon per jam jar. Test, test, test. You may have to treat the back too, to get a good colour match.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au



These users thanked the author Trevor Gore for the post: Dmaxwell (Wed May 02, 2018 11:47 pm)
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PostPosted: Wed May 02, 2018 11:44 pm 
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Brazilian Rosewood
Brazilian Rosewood

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First name: Ed
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Thanks very much!


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