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Forum topic by newwoodbutcher posted 05-20-2016 06:04 AM 977 views 0 times favorited 6 replies Add to Favorites Watch
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774 posts in 3024 days

05-20-2016 06:04 AM

Long sad story shortened. African Mahogany treated(over treated) with Potasium Dicromate. It’s way too dark. Also, on top of the PD are two coateds of Liberon Finishing oil. Way too much detail to sand and start over. Is there some kind of acid or solvent that will lighten the color of the wood?

-- Ken

6 replies so far

View Kelly's profile


2103 posts in 3118 days

#1 posted 05-20-2016 07:37 AM

Can you test hydrogen peroxide? You can get 35% from a health food store. You have to neutralize it when done.

View newwoodbutcher's profile


774 posts in 3024 days

#2 posted 05-20-2016 08:52 PM

Good tip, I’ll try that, thank you.

-- Ken

View pintodeluxe's profile


5783 posts in 2987 days

#3 posted 05-20-2016 09:22 PM

Is this planks of lumber or an assembled project? If it is still planks, you could take a skim pass through the planer.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View JayT's profile


5926 posts in 2385 days

#4 posted 05-20-2016 09:44 PM

Try oxalic acid. It’s the main ingredient in several brands of wood bleach/cleaner and also in Barkeeper’s Friend.

-- In matters of style, swim with the current; in matters of principle, stand like a rock. Thomas Jefferson

View Kazooman's profile


1215 posts in 2126 days

#5 posted 05-20-2016 10:04 PM

I can’t offer any ideas for you to fix your problem, but I feel I should take the opportunity of this thread to remind all of my fellow woodworkers to respect the chemicals they might be using in the shop. I often get the impression that many do not appreciate the hazards associated with using some of these materials. I am not saying that the OP does not appreciate the issues, but it is a good chance to remind everyone to be careful.

Chromium is BAD news. Chromium salts are flat out very acutely toxic and they are also proven carcinogens. They need to be handled properly with sufficient personal protection measures and then the residual material needs to be disposed of properly. The latter issue really concerns me. In an industrial setting any chromium containing waste stream would need to be segregated, properly contained and labelled, and then a certified waste disposal company would be paid an enormous sum to remove and properly treat the waste. What becomes of the chromium residues from staining wood?

The Internet can provide a wealth of references to the toxic effects of chromium. An easy one is Wikipedia. Not my usual choice for hard facts, but I think they got this about right. Here’s a cut and paste:

In 2005–06, potassium dichromate was the 11th-most-prevalent allergen in patch tests (4.8%).[9]

Potassium dichromate is one of the most common causes of chromium dermatitis;[10] chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and fore-arms, which is chronic and difficult to treat. Toxicological studies have further illustrated its highly toxic nature. With rabbits and rodents, concentrations as low as 14 mg/kg have shown a 50% fatality rate amongst test groups. [11] Aquatic organisms are especially vulnerable if exposed, and hence responsible disposal according local environmental regulations is advised.

As with other CrVI compounds, potassium dichromate is carcinogenic and should be handled with gloves and appropriate health and safety protection. The compound is also corrosive and exposure may produce severe eye damage or blindness.[12] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children.

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3596 posts in 2163 days

#6 posted 05-21-2016 08:05 PM

Kazooman…..i hope that people will take notice of your post. The MSDS backs up your warning and it is a very hazardous material.

Be careful out there in your shops.

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