Potassium Dichromate on Mahogany Cameras

[Mark Sawyer]

I've been reading about using Potassium Dichromate as a "stain" on mahogany on the woodworking forums in preparation for a camera project. It's not really a stain, but an oxidizer that darkens the wood. It was used quite a bit in the old days, as it is less likely to be blotchy and gives a nicer result, (it doesn't muddy the grain like a conventional stain).

Unfortunately, it's also toxic, carcinogenic, and can be absorbed through the skin or respiratory system. That kinda puts me off on using it. But it also makes be wonder, as it was used on many of our older cameras and other wooden ephemera, is there a danger of absorbing it through handling equipment that has an oil finish instead of being sealed by lacquer? Is it an issue when refinishing cameras? From what I've read, it doesn't break down much over time...

[Jim Noel]

If there was a danger in handling old wooden cameras treated with dichromate, i wouldn't be alive. I have been handling such cameras for over 75 years.

[Sal Santamaura]

..., is there a danger of absorbing it through handling equipment that has an oil finish instead of being sealed by lacquer? Is it an issue when refinishing cameras? From what I've read, it doesn't break down much over time...

I have no expertise that would enable a valid answer, but...

If there was a danger in handling old wooden cameras treated with dichromate, i wouldn't be alive. I have been handling such cameras for over 75 years.

I am certain that Jim's answer is no more valid than the claim of someone who says "I've been smoking for 75 years and don't have lung cancer. There's no danger in smoking."

There are too many factors related to individual genetics for such extrapolation to be wise. Hopefully, someone who really knows the answer will post.

[Greg]

http://forums.finewoodworking.com/fi...gcoloring-wood
https://www.shellac.net/POTASSIUM_DICHROMATE.html
http://www.woodweb.com/knowledge_bas..._the_risk.html
http://www.emgw.org/Resources/Docume...icalStains.pdf

think I'll stick to Minwax....

[LabRat]

The main reason for staining wood is that if one just finishes hardwood and applys a finish, that even from the same species of wood that there is a very great difference of the color/depth/and look of the wood, so from a mfgs point of view (that are selling a product that is uniform looking), a way that will even out major differences is desired...

Dichromate is very orange, but darkens from light/age and penetrates well and evenly, and will even out many differences in wood... If surfaces are sealed, even tung oil should provide a barrier from contact... It would transfer the color to one's hands quickly (and there is the well known industry term "dichromate poisoning" ) so if it couldn't be sealed, it would not be used at all (even in the "bad old days")... Probably a bigger issue if used for something that gets a lot of handling, like musical instruments...

You probably have a bottle in you darkroom chem locker you can try, but I expect it would be more toxic to apply, but benign while it sits there (and used) over many years... But it can be handled safely, even in liquid form (I have a brief foray into holography where it is used to form the image)...

Steve K

[Mark Sawyer]

http://forums.finewoodworking.com/fi...gcoloring-wood
https://www.shellac.net/POTASSIUM_DICHROMATE.html
http://www.woodweb.com/knowledge_bas..._the_risk.html
http://www.emgw.org/Resources/Docume...icalStains.pdf

think I'll stick to Minwax....

Yup, read those, and more. All kinds of answers, from "wear a respirator, facemask and gloves, and only open the container outdoors while standing upwind" to "don't worry about it". Potassium Dichromate is also used in photography for gum printing, carbon printing and photogravure, with varying sorts of precautions taken.

I'd like to use it, but yeah, Minwax sounds safer. I also have a couple of old studio cameras that someone before me lightly refinished with just an oil finish (no lacquer or polyurethane type sealers). Should I seal them or handle them minimally?

Yeah, probably worrying to much...

[Mark Sawyer]

If there was a danger in handling old wooden cameras treated with dichromate, i wouldn't be alive. I have been handling such cameras for over 75 years.

I've only been handling them around 40 years. But a coat of lacquer or such might mitigate the problem. What about an oil finish? Or does it reduce to something else after oxidizing the wood? If I do use it, is there something to treat the wood with after darkening to eliminate the worries?

I have former students now it their early 20's who may handle the cameras too...

[Mark Sampson]

I'd forget about it and go do some gum printing. It was in the late '70s when I took a gum printing class- IIRC you use potassium dichromate as a sensitizer in that process. We did use rubber gloves, but I never produced anything I liked, and have never gone back to it.
On-topic, perhaps, there's a hell of a lot more old mahogany furniture out there than there are wooden view cameras. If there was indeed a problem, might we not know about this already?

[Mark Sawyer]

On-topic, perhaps, there's a hell of a lot more old mahogany furniture out there than there are wooden view cameras. If there was indeed a problem, might we not know about this already?

Quite right. But this is the twenty-first century, and everything is going to kill us...

[Harold_4074]

Potassium dichromate is a strong oxidizer, and all of the "drying oils" used in traditional varnishes are strong reducing agents (cellulose is no slouch, either) so it is very unlikely that you are going to be poisoned by potassium dichromate leaching through an old finish. A modern polymer? Maybe, but unlikely, since the salt is water-soluble and these finishes are usually formulated to be waterproof.

A stronger consideration might be the resale value to a person who believes that anything hazardous on an industrial scale will also be lethal just due to proximity. Trying to explain reality to some of these people may shorten your life expectancy more than exposure to the hazard under discussion. (Stress and frustration are not good for your cardiac health )