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tango

Working with potassium dichromate.

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Hi

This is my first time.
Do you seal the wood before apply dicromate?
I will test in crap wood first with seal and without.
Thanks in advance for any advise.

Regards

Tango

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I haven't used it in a long time, but when I did I didn't seal the wood.  I think it has to contact the wood to have any effect.  It is not a pigmented stain -- it works by chemical reaction.  Initially the wood becomes an obnoxious yellow and later becomes brown.  Yes, try it on (s)crap wood first.

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38 minutes ago, tango said:

Hi

This is my first time.
Do you seal the wood before apply dicromate?
I will test in crap wood first with seal and without.
Thanks in advance for any advise.

Regards

Tango

How can it kill you?  Let me count the ways...... 

Emergency Overview
--------------------------
DANGER! STRONG OXIDIZER. CONTACT WITH OTHER MATERIAL MAY CAUSE A FIRE. CORROSIVE. CAUSES SEVERE BURNS TO EVERY AREA OF CONTACT. HARMFUL IF SWALLOWED OR INHALED. AFFECTS THE RESPIRATORY SYSTEM, LIVER, KIDNEYS, EYES, SKIN AND BLOOD. MAY CAUSE ALLERGIC REACTION. CANCER HAZARD. CAN CAUSE CANCER. Risk of cancer depends on duration and level of exposure.

https://www2.atmos.umd.edu/~russ/MSDS/potassium_dichromate.htm

:rolleyes::huh:

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I would love to have someone break down the differences/uses/dangers of..
Potassium Permanganate

Potassium Dicromate
Potassium Nitrate
Potassium Nitrite

Any takers?

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Speaking of potassium dichromate.   Most will have noticed that it sometimes has a greenish cast.  This is from some oxide of chromium and results because the reaction in the wood does not go to completion.  

This is corrected by Carl Becker's stain.  This has the dichromate in an acid buffer solution involving dilute nitric acid and boric acid.  

It is not a Becker "secret."   Buffer solutions are commonly used in chemistry.

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1 hour ago, DoorMouse said:

I would love to have someone break down the differences/uses/dangers of..
Potassium Permanganate

Potassium Dicromate
Potassium Nitrate
Potassium Nitrite

Any takers?

All of the substances above are hazardous, starting with the dichromate, which is a nasty bitch-kitty of a toxic reagent.  It's strictly an over-the-top oxidizer used in organic chemistry (as in it can oxidize you), and considered too corrosive, toxic, irritating, and carcinogenic for anything else *, except, apparently by luthiers.  The permanganate is close in oxidation ability (so it's a corrosive fire hazard, too), but less hazardous in other ways, and much more useful.  It's used for a lot of things in weak solution, such as water treatment and as an antifungal.  Both of these powerful oxidizers are hypergolic (burst into flames) with certain organic substances and are a fire hazard.

Potassium nitrate, commonly known as saltpeter, is a weaker oxidizer, and the principal constituent of gunpowder.  Along with the nitrite, it's used in curing meat, such as ham, sausages, and bacon.  Yes, both chemicals have ingestion hazards which have to be considered.

My advice is to Google all of them and begin thoroughly studying what comes up (starting with the Wikipedia articles) before you seriously contemplate playing with any of them.  :rolleyes::)

* Because someone is bound to bring it up, yes, there are leather tanning, dyeing, cement, and photographic recipes which have used it, but considering it's a Cr +6 compound, go find a less toxic substitute, particularly if you don't understand what I just said.  :P

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In the Becker formula, the nitric acid acts as a developer. You can accomplish the same thing with less danger (I won't have nitric acid in my shop) by using UV light. The boric acid, for whatever reason, changes the final color to a tan instead of green, at the expense of darkness of result. 

Yeah, don't drink the dichromate, but for about a century silk screeners bare-handed it up to the elbows without recognizable problems (no silk screen equivalent of black lung disease, for instance). I know that being scared is very much in fashion these days, so if you're the frightened type, here's your chance. Start here, since it's the main ingredient in most stains: http://dhmo.org/

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4 hours ago, DoorMouse said:

I would love to have someone break down the differences/uses/dangers of..
Potassium Permanganate

Potassium Dicromate
Potassium Nitrate
Potassium Nitrite

Any takers?

Ya, its called google....type any chemical name in followed by MSDS, for example

Potassium Nitrite MSDS

MSDS= material safety data sheet

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Hi Tango.

I use all three from time to time. I've had the same little pots of bichromate of potash  and permanganate of potash for thirty years , and they'll see me out. I mainly use them for repair work, very dilute, to bring new wood up to colour. Bichromate gives a nice golden brown, but be careful around maple that's been baked or bent on the bending iron -  it can go pink. Permanganate gives a different  colour. I was told that those Mirecourt trade fiddle necks were treated with it. It starts more brown, but deteriorates to slightly grey with a hint of green. Under varnish in very  dilute washes I think it's fine and very useful. 

From  time to time I miss the mark on the ground coat for a violin, and need to darken it, or must wash  off the varnish for some reason, and damage  the  ground.  I'll clean the surface completely with acetone,  so that water will  grip, and not run off in beads. Then I'll use very dilute  washes of both to rescue my ground. They're very very good for this!

I use nitrite more,  as part of my making process. 

I dont worry about the safety aspects at all, just treat them as poisons. I mix tiny amounts - a few crystals on the tip of the brush mixed on the palette, or a pinch in a small  jar - never more than needed.

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1 hour ago, Conor Russell said:

I use all three from time to time. I've had the same little pots of bichromate of potash  and permanganate of potash for thirty years , and they'll see me out. I mainly use them for repair work, very dilute, to bring new wood up to colour..........................

I dont worry about the safety aspects at all, just treat them as poisons. I mix tiny amounts - a few crystals on the tip of the brush mixed on the palette, or a pinch in a small  jar - never more than needed.

This sounds good to me.  I just wanted to make sure that everybody out there reading this realized that the potassium dichromate is poisonous, and a powerful oxidizer that has to be treated with care.  :)

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I am interested in historical applications. I don’t think any of the chemicals cited above (except boric acid perhaps) were used by Cremonese makers. If anyone has evidence to the contrary, please share.

Anyhow, they are pretty nasty oxidizers and should be handled carefully as @Violadamore said.

Having said all of this, I encourage makers to experiment. 

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Chromium III oxide is used as green ink in money and  and is what you get when you reduce the higher oxide. While experience trumps theory I can't say I am crazy about using something that would leave such highly colored residues.

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3 hours ago, avandesande said:

Chromium III oxide is used as green ink in money and  and is what you get when you reduce the higher oxide. While experience trumps theory I can't say I am crazy about using something that would leave such highly colored residues.

So use dichromate in an acid buffer.  What is the problem?

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1 hour ago, Johnmasters said:

So use dichromate in an acid buffer.  What is the problem?

Sure, go for it. But many of us prefer materials that have tendencies aligning with the final result. It's a kind of simplifying.

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53 minutes ago, avandesande said:

Sure, go for it. But many of us prefer materials that have tendencies aligning with the final result. It's a kind of simplifying.

I'm not sure what you mean.

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The tendency of dichromate + boric acid is towards brown/tan. Thus, no problem

Things have many "tendencies". For instance one tendency of water + human is drowning, but you aren't obligated to take that particular path when you handle water.

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Potassium dichromate seems to produce the same effects as potassium chromate. I used the latter on a couple of my first fiddles with mixed results. Can anyone tell me what difference there is in both use and toxicity?      

 

 

 

 

 

 

 

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15 hours ago, Violadamore said:

This sounds good to me.  I just wanted to make sure that everybody out there reading this realized that the potassium dichromate is poisonous, and a powerful oxidizer that has to be treated with care.  :)

Hi.

Thanks you all for useful information.

 

Viola D´amore.

You scare me :). Y sincerely thank you for your caveats. I was thinking to use gloves and mask but now I will read more about safety.

For the first stage on a white violin I was thinking to make half a litre of very diluted glue with a little spoon of Potassium Dicromate.

What do you think?

Of course I will try first in crap wood.

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1 hour ago, tango said:

Hi.

Thanks you all for useful information.

 

Viola D´amore.

You scare me :). Y sincerely thank you for your caveats. I was thinking to use gloves and mask but now I will read more about safety.

For the first stage on a white violin I was thinking to make half a litre of very diluted glue with a little spoon of Potassium Dicromate.

What do you think?

Of course I will try first in crap wood.

I'd advise dissolving the dichromate in a small amount of water first, then mix the two solutions outside, down wind, and away from structures, until you know what it will do.   Shouldn't be a problem done with dilute solutions,, but the glue will oxidize, and adding the concentrated dry chemical to it could cause explosive splattering from rapid oxidation at the surface contact.  My major worry was that someone would innocently mix some +6 or +7 oxidizer with volatile varnish components and create a fireball.

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I only use Potassium Dichromate on necks and always apply Tannic acid or strong tea and let it dry then put on the dichromate. Putting it in the light box or outside in the sun for a few minutes will make it darker and less yellow.

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8 hours ago, avandesande said:

Sure, go for it. But many of us prefer materials that have tendencies aligning with the final result. It's a kind of simplifying.

Yes,  prevent the formation of oxides of Chromium.   You have to know why you wound up with the oxides in the first place.  (The dichromate-tannin reaction did not go to completion.)

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On 2/28/2020 at 10:26 PM, jezzupe said:

Ya, its called google....type any chemical name in followed by MSDS, for example

Potassium Nitrite MSDS

MSDS= material safety data sheet

 Since this is a topic that resurfaces fairly frequently and has potential safety risks, I thought it would be beneficial to the community to have this info all in one place as a reference.  
 Thanks Violadamore and others for generously providing that information.

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35 minutes ago, DoorMouse said:

 Since this is a topic that resurfaces fairly frequently and has potential safety risks, I thought it would be beneficial to the community to have this info all in one place as a reference.  
 Thanks Violadamore and others for generously providing that information.

In my mind it is already, the government mandate that requires  all chemical and chemical formulas being sold or used to have material safety data sheets available to the general public is the "one place" the one place is the "keyword" MSDS, again by typing the name of the chemical or product with the addition of "MSDS" will give you all the information you could need about the chemical

again using my example

https://fscimage.fishersci.com/msds/19480.htm

the second google link, and as wonderful and intelligent as our Viola is, this information is more complete simply because it is mandated by law to be "everything" one could know about the product.

 it really isn't that hard to type MSDS along with the chemical name in the google search bar and it doesn't seem to make sense to waste valuable storage space here when it's already readily available elsewhere just by using the magic "MSDS" keyword , all one need do is remember "MSDS" and know what chemical they are trying to find

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