Potassium Dichromate

[Don Sforza]

I recently scored some pattern-grade Honduras Mahogany and have a couple of projects planned. Not being a "stain everything and slather it with poly" guy, I wanted to try potassium dichromate. In a word... holy cow. OK that's two words.

I mixed a very weak solution and tried it on some mahogany scraps and also some cherry. I got the expected results with the mahogany, but the cherry astounded me! With one application on the cherry the wood turned a deep dark brown... not a color I'd like on a cherry piece typically, but for matching older cherry pieces this may be just the trick.

So the question is: Have any of the wood dorkers out there had the same experience as me? How about other woods?

Don

[cselby]

[Jay Pique]

[Marilynn or Bruce Pearce]

Through yahoo shopping

[fredfighter]

A word (or a few) of caution.

Potassium dichromate is a powerful human carcinogen and a strong oxidizer. For the former reason it has almost entirely been phased out

of industrial uses.

It is probably illegal to dispose of it by pouring it down the drain. Though you are not likely to get prosecuted, that is really not the point.

Probably it would be prudent to do a little reasearch and find a way to treat it to make it safer for disposal. That _may_ be as simple as mixing it with portland cement and then throwing the solid chunk into the garbage.

Perhaps a real chemist can comment further.

I read, in a book on router techniques, of a similar process using nitric acid. One wets the wood and then heats it with a heat gun until the desired darkening is achieved, then neutralizes with a sodium bicarbonate (baking soda) solution. That process generates nitrogen dioxide which can be quite deadly, but neutralizing and disposing of the unused solution is quite trivial.

As with most of life's hazards, there is no rational reason to be afraid to try these things, one just needs to understand the dangers and how to mitigate them.

[Joe Gorman]

[bent]

If you get a relatively cheap wood to become black in the future would you make a post of it for me.

[Jay Pique]

Burn it. I use a heavy duty propane torch designed to burn brush. Nice big round flame makes it pretty easy to scorch it evenly.

India ink.

Aniline dye and black pigmented stain.

JP

[Joe]

You might be confusing this with another potassium compound. I assume he refers to K2Cr2O7 which is useful in photographic processing among other uses, and, as a matter of fact, is the active ingredient in an over-the-counter headache remedy...cannot remember the name. Basically it is an oxidizer.

[wood_newbie]

Not correct at all. Read the MSDS on potassium dichromate.

Toxic as all hell, and a very well-known carcinogen.

[Unquestionably Confused]

Amen. Anyone here constipated? This will make you crap!

Search your memory or dig up a manual or packing list for one of the old A.C. Gilbert, et al., chemistry sets sold as handy dandy birthday or Christmas presents back circa 1956. I can still recall mine and bottles of nifty things like Benzine, Sodium Bisulphate, Copper sulfate, etc. Those are all bad enough. I wonder what else was in there that I have forgotten about.

Can you just imagine marketing something like that now? It would be enough to make half the world's attorneys drop dead of heart attacks and have the other half of them rubbing their hands together so hard they'd bleed.

[fredfighter]

Trivalent chromium is an essential nutrient and might be found in a headache medecine. Hexavalent chromium is quite toxic but fortunately, poorly absorbed via the digestive track (due to the pH of stomache acid) for most people. Inhalation of the dust is another matter.

[Enoch Root]

There's a wide range of pH levels along the gut. Metals pass through the lining via mechanisms for which there is, very likely for any heavily oxidized form of chromium, no specific one.

Neither is there one in the lungs, but there's also less protective glycoproteins or proteoglycans, and less transient flotsam lying about for the ion to bind with or associate with, no flora that might have an interest in it, and there's no exit if the cilia can't beat it out.

I'm just guessing though, and I could be wrong. :)

er

[Baron]

As a "real" chemist, I can tell you that K2Cr2O7 is potassium bichromate (or dichromate, whichever you prefer). It is a highly corrosive poison. I'd love to know the source of your statement that it is in a headache remedy. Chromium in all it oxidation states has been found to be carcinogenic. It is a matter of its physical form and how you are exposed to it. Please keep in mind that arsenic and selenium are also necessary trace elements. I wouldn't go around eating arsenic and chromium salts by the handful.

As for using it to stain wood, there is no reason to do so. These type of things were used long ago before the advent of modern light fast stains. If the old-timers had modern stains, I am sure they would have used them in preference to "chemical" stains.

I would be careful about using nitric acid to stain wood. A nationally recognized expert in finishing used some once on a test block of wood. Several years later, he cut through the piece. He was surprised by the extent of penetration and how he could still smell the by-products of the nitric acid. Disposal of nitric acid, while easier than chromate salts, is not trivial. It must be carefully neutralized and the resulting nitrate salts must be dealt with.

[George E. Cawthon]

Must be an old chemist to call in bichromate. :) Nonetheless I certainly agree with your statements on chromium. Don't agree with your statement on arsenic being an essential trace element.

Nitric acid disposal may be a problem but only for industrial use, especially if it is contaminated with dissolved metals which it often is in industry. Nitrates and nitrites are a problem when they leach into groundwater but the problem is mostly from agriculture (excess fertilizers and stock waste). At least in small amounts the natural nitrogen-- nitric--nitrate cycle in the soil will take care of nitric acid. Depending on where you live, soils will quickly neutralize nitric acid, plants will take up the nitrates and soil organisms will change the excess to nitrogen gas.

[Doug Miller]

FYI...

"... Boron, chromium, manganese, nickel, tin, vanadium, molybdenum, arsenic, lithium, aluminium, strontium, cesium and silicon are regarded as new trace elements in the sense that they have only recently been considered essential in human diets...."

[Renowood]

Check ebay for Potassium Dichromate. It goes for $6-$9 per pound.

Renowood

[George E. Cawthon]

I think I'll reserve judgment. That statement doesn't really make sense. An element has either been demonstrated as essential or not. There are several way that is possible, e.g. lack of the element causes a disease or other problem, the element is an integral part of an essential molecule or needed to activate the molecule, etc. "Considered essential" doesn't mean much. I'm not current on the subject, but some of those element mentioned are highly suspect.