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
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?
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
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
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.
On 7 Apr 2006 08:47:26 -0700, firstname.lastname@example.org wrote:
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
Basically it is an oxidizer.
wood email@example.com, or somebody so disguised, wrote the following at
or about 4/7/2006 5:01 PM:
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
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
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.
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. :)
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
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.
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
"... 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...."
Doug Miller (alphageek at milmac dot com)
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.
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