View Full Version : Potassium Dichromate?

Jan-25-2004, 4:36pm
Has anyone used Potassium Dichromate? I see Dude uses it before he finishes his mandolin!

Bob A
Jan-25-2004, 4:57pm
Nasty toxic carginogenic stuff.

Don't use it as you value your life.

Jan-25-2004, 5:05pm
I was trying to find you a recent thread on this but could not find it. This stuff is as bad as chrome plating.

There was some results with steelwool in vinegar for use on maple to enhance grain.

Jan-25-2004, 6:44pm
steelwool and vinegar... hmmm does it work pretty well? does anyone know of some other trick to get the grain to jump out?

Jan-25-2004, 7:26pm
Apart from the hazards listed in earlier posts I believe it is also a strong oxidizer which will cause spontaneous combustion if it comes into contact with a flammable liquid.

Instant fire.

Chris Baird
Jan-25-2004, 8:14pm
Watch out Dr. Cohen is gonna come and sock it to ya. It is my belief that you can work with it safely, however, the work to ensure saftey is not even close to being worth the results. My new favorite grain enhancer is cooked down pinion resin disovled in alcohol lightly wiped over the raw wood then sanded down evenly. It enhances the figure contrast but doesn't "dirty" it up.

Jan-25-2004, 8:16pm
Another trick that some violin makers use is to make a strong tea using several teabags in a cup, then paint the wood with the tea and hang the instrument in a large plastic bag (a garbage bag will do) with an open container of household ammonia sitting in the bottom. Close it up and check ever so often until the wood has been darkened to your satisfaction. To be honest, I haven't tried this yet, but I do know of two different makers who do this. Of course you should try it out on some test strips first...


Jan-25-2004, 8:36pm
are you serious woody? #sounds like a pretty interesting method... have you gotten a chance to see their results? #these are interesting replies... Thanks http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif

Jan-25-2004, 8:49pm
I was given some sort of grain enhancing chemical many years ago by a gun stock builder when I was first starting out building instruments. It worked. There are several chemicals that will work, and I've used other oxidizers on curly maple over the years, but I've found that wood stain does a better job for me.
The old Siminoff book has a good discussion on "building contrast" and why and how it works. If I use my aniline stains I have better control of the color I end up with, as well as the amount of grain enhancment. These stains are toxic too of coarse, so however you do it, be careful.

Michael Lewis
Jan-26-2004, 1:33am
One really safe way of enhancing the contrast of the wood grain is to sand it through 800 grit or even finer. Just do it on a test piece of scrap wood to prove it to your self. The finer the grit you use the more translucent the surface of the wood becomes.

Dave Cohen
Jan-27-2004, 10:15am
You can easily Google this up, but here is a url for those who believe that Chromium(VI) can be worked with safely.


When you get to this, look in "Section 8 - Exposure Controls & Personal Protection". "Local Exhaust" means a fume hood. Do you have one of those in your shop? Can you afford to discard your shoes after every time you use the stuff?

Tom C
Jan-27-2004, 10:30am
It tastes great in chocolate milk too.

JD Cowles
Jan-27-2004, 12:07pm
hey woody-

i've used ammonia to "fume" oak in making reproduction arts & crafts furniture. #it produces a beautiful color on quartersawn oak, but i've never tried it on other woods. #perhaps the tea contains the same chemicals that oak does and will give the appropriate reaction with the ammonia. #if you do this, use caution as ammonia is nasty stuff. #do it outside if you can, and wear a respirator when you open the bag (i've used plastic trash barrels).


oh yeah, i agree with micheal about sanding. as tedius as it can be, it can produce some stunning results.

Jan-27-2004, 12:59pm
From what I understand about it, it is the tannins in oak that react with the ammonia. There are tannins in tea, so It stands to reason that tea on or in the surface of maple would darken in the presence of ammonia. It doesn't sound like it would be very easily controllable, but maybe it's a slow enough process that all you have to do is keep watch and stop when it looks right.

Jan-27-2004, 2:03pm
"does anyone know of some other trick to get the grain to jump out? "

Using very figured wood helps....:)

Dru Lee Parsec
Jan-27-2004, 5:08pm
In an old Fine Woodworking magazine there was an article on making the grain in Maple pop. I believe it was written by Jeff Jewitt. Here is his basic process:

Make a maple stain with water based pigments. Make it a diluted stain with about twice as much water as it would normally take. Wash coat the entire piece. This will do two things, It will darken the piece and raise the grain.

Sand with 320 to 400. What you are doing is to sand off the raised grain which is the lighter pithy part of the wood. That essentially leaves the stain in the darker grain and you sanded the stain off of the lighet grain. Basically you just increased the contrast.

Now he uses an oil base to his finish. So he then flooded the piece with as much Tung oil as it would take. Once the wood took as much oil as it could he hand rubbed on a french polish of shellac. The oil treatment may or may not be appropriate on an instrument. But the staining/sanding step could certainly be useful. If you don't get the contrast you want then tray again with a stronger dilution.

If I can find the exact issue of Fine Woodworking I'll let you know which one it is.

Joe F
Jan-27-2004, 5:30pm
Potassium dichromate must be some nasty stuff. #Note in particular section 5 of Dave Cohen's MSDS link, regarding fire fighting measures:

Extinguishing Media:

Feb-01-2004, 3:32am
I use Potassium Dichromate all the time, but to standardize other solutions. As others have pointed out, there are risks involved in handling it, but it can be done safely. I don't know how it's used to treat wood though. fill me in and I might be able to make some suugestions on how to handle it.

A big negative is that it's classed as a hazardous compound, so disposal of the waste can be a problem unless you work in a lab.

Feb-01-2004, 8:40am
Check out this website:


Otis Tomas has a *great* website! If you check out his "Reflections" link #and read "On Varnishing a Violin", his preparation of the wood describes how the wood should be scraped and then treated with tea and ammonia to better show grain contrast.

For folks coming from a mandolin or guitar building tradition, this whole site is a nice perspective on how some violin makers work. Imagine going out your door and scraping resin off a tree trunk and making your own varnish! (BTW, the oil varnish violin makers use is a whole nuther thing from what most mandolin makers call a varnish finish) This fellow is a true artist both in wood and music. I learned a waltz he wrote called The New Land, which is as beautiful as his instruments.


Feb-01-2004, 11:11pm
I am thinking on trying the (tea and ammonia) trick. questions: Would you do this on the spruce front too? I am thinking not since there is no real grain pattern in it to speak of, just horizontal lines all the same. On the maple end of the deal, when would you do this? When doing the final sanding before staining? or can you do it earlier? Do you also do the neck and rim??
What does it do after you sand it? Does it turn the the wood back to the original color except darken the grain lines? Or will the entire piece be darker? Thanks for any help, JD

Michael Lewis
Feb-02-2004, 2:06am
Concerning ammonia, you can use household strength (3% - 5%), easily obtainable at your local super market. My suggestion is to suspend your instrument in a tent, garbage bag, etc. over a container of the ammonia. Since ammonia exists mostly as a gas, not a liquid, it evaporates readily to form a fairly strong concentration of the gas in the enclosure. This is what works best to change the color of the wood, not wetting the wood with the liquid. Pre treat the wood with tanins like tea or oak bark, and let the wood dry before subjecting it to the ammonia, as the ammonia react with the tannins. DO NOT USE AQUIOUS AMMONIA like agricultural fertilizer. It is the same chemical but so much stronger that it can easily burn your skin and lungs.

Feb-28-2004, 12:49am
Michael Lewis---->One really safe way of enhancing the contrast of the wood grain is to sand it through 800 grit or even finer. Just do it on a test piece of scrap wood to prove it to your self. The finer the grit you use the more translucent the surface of the wood becomes.

Hey Michael: I agree, however I was once told not to sand a mandolin any futher than 220 grit or the stain wont soak in properly. Is this a myth? I find 220 pretty rough still.
I would like to try going up to 600 or so on my current mandolin. Is this OK too go this high a grit? Or is there any truth to the 220 grit rule that I was told.

Feb-28-2004, 8:27am
Just chiming in here, tho the question wasn't directed to me. I've mentioned before that I worked for a manufacturer for many years and 6 of those years were in the finish room. Sanding beyond 220 grit before finish is a waste of time in that there is no difference in the look of the instrument with a sprayed finish applied. If you're using a rubbed oil finish or something you might get some benefit from more sanding. I, for one, don't want to sand and more than I have to.

Michael Lewis
Feb-29-2004, 3:32am
Always try a new process out on scrap wood to find out how it works for you. It's amazing what you can learn by trying things. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/coffee.gif http://www.mandolincafe.net/iB_html/non-cgi/emoticons/cool.gif

Feb-29-2004, 9:58pm
I make violins, and I use it on top of a ground coat, it comes out a nice brown color. Most violin makers don't stain the raw wood, they add the color to their varnish. It is very toxic care must be used in using dichromate. It is also used on the inside of the instrument too! It works as a pesticide, and some say it helps with humitity! I have never hear of a violin maker using tea and ammonia to stain his wood, that seems to me that it could break down the glue joint.