Ammonium Dichromate replacement for Carbon printing

[gth]

The toxicity of ammonium dichromate puts a bit of a potential damper on carbon and gum printing, especially if one want to work in Europe, where availability might soon become a real problem. Ammonium Dichromate can't be shipped by air, its a strong carcinogen etc. the whole bit… What about residual dichromate in the carbon print for instance…. if it is a carcinogen it's only a matter of time before it will be branded.

Well first….. am I right in that statement….. how big a problem is this in real life???? I have zero experience at this point.

There is a process floating around called the The Chiba System.

It use Ammonium ferric citrate as the sensitizer and 0.3 % Hydrogen Peroxide as developer. Both largely non toxic especially compared to Ammonium Dichromate.

Is this process for real or just BS….. Would be interesting the hear what the real pros doing carbon printing here has to say about this.

And how does it effect the quality and archival properties of carbon prints?

See

http://www.google.ca/url?sa=t&rct=j&...bqsJyV9VG5npig

[Pete Watkins]

i've posted about this before. From September 2017 Ammonium and Potassium Dichromates WILL be banned throughout the EEC by the European Parliment.
These chemicals are allegedly so deadly that we can use them until 2017, which gives a clue as to the mentality of the idiots who are banning them.
I don't believe that they have any idea about the consequencies of this ban. This stuff, in my opinion, is no more deadly than the petrol (gas) that you put into the fuel tanks of your cars.
Potassium Dichromate is not highly flammable but those who govern us still intend to ban it.
If anybody knows of a replacement chemical suitable for use in Gum printing or certain Cyanotype formulas please share your knowledge.
Pete.

[gth]

Pete,

Check out the link I put in my first post.

It gives supposedly an alternative to Ammonium Dichromate. Which apparently is a strong carcinogen……. I don't know what the facts are.

BUt I am very interested in working with carbon printing and one reason is that carbon print development do not use any chemicals….. only water…… So dichromate problems and regulations is not something I can take lightly, going forward. If I go ahead with carbon printing it's something I'd like to stick with and get good at so I need to know I won't have problems with dichromate issues in my prints. And I am fully aware that dichromate has been used for over 100 years.

It will be interesting if anyone of the skilled carbon print practitioners here will address this issue and the alternative process.

I feel bad about crashing the party like this, but there you have it…..

/gth

i've posted about this before. From September 2017 Ammonium and Potassium Dichromates WILL be banned throughout the EEC by the European Parliment.
These chemicals are allegedly so deadly that we can use them until 2017, which gives a clue as to the mentality of the idiots who are banning them.
I don't believe that they have any idea about the consequencies of this ban. This stuff, in my opinion, is no more deadly than the petrol (gas) that you put into the fuel tanks of your cars.
Potassium Dichromate is not highly flammable but those who govern us still intend to ban it.
If anybody knows of a replacement chemical suitable for use in Gum printing or certain Cyanotype formulas please share your knowledge.
Pete.

[desertrat]

If the dichromates can't be successfully replaced, there is a UK based Ebay vendor selling a set of instructions describing how to make potassium dichromate from readily available chemicals. I'm aware of a 19th century process that uses chrome green pigment (Cr2O3), potassium carbonate, potassium nitrate, a crucible, and a furnace. I think the process for sale on Ebay uses the ingredients in solution at room temperature.

[sanking]

The Chiba System is interesting but not a satisfactory replacement for dichromate in carbon printing IMO.

More promising is a chemical called DSA, 4,4'diazidostilbene, called DSA. Long thread on the subject on APUG, http://www.apug.org/forums/forum42/9...-transfer.html There are pros and cons associated with a DSA workflow, but for the time being the cons prevail in the balancing act that I make.

My personal opinion is that the use of dichromate in carbon printing does not pose a serious health issue for the worker, assuming reasonable precautions, and that the small amounts that are used are easy to neutralize and dispose of without risk to the environment. In the past carbon printers used wasteful tray sensitizing that resulted in the disposal of a fair amount of dichromate in the environment, but today most serious workers use some form of brush or roller sensitizing that uses a very small amount of very diluted dichromate solutions to sensitize. For example, in my own work flow I use only 30 ml of a 3%-6% solution of dichromate to sensitize with a roller a 20" X 25" sheet of carbon tissue. That amounts to about 0.4 - 0.8 grams of dichromate per print this size, with no waste. If you do the math you will see that even if you print extensively with carbon over the next three decades your total use of dichromate will not amount to more than 4-5 pounds.

Sandy

[cyrus]

Huh, so how does one get into the dichromate "importing" business in the EU, someone not me would wonder, toottaly not me.

[Nathan Potter]

Early in my career I used large amounts of Ammonium and Potassium Dichromate to oxidize the surface of molybdenum thin sheets to be used for metal mask manufacture. The handling was careless and the total volume over a few years was tens of pounds. In retrospect that was a very unwise process but hey, I'm 80 now and never have had any discernible side effects from the exposure.

I'm guessing that the EU is more concerned about the possible buildup of Dichromate in the environment but cannot find a solution except to outright ban the material.

Nate Potter, Austin TX.

[sanking]

To address another concern mentioned by the OP, carbon prints would not normally contain any dichromate after processing. During processing some dichromate leeches into the fiber of paper prints but this is normally removed by soaking the print for a few minutes in a solution of sodium or potassium bisulfite/metabisulfite.

Sandy

[gth]

Thanks Sandy I was just about to ask those specific questions, that is. how much residual dichromate is retained in the print itself. Personally I don't have problem of handling the stuff in the darkroom in a responsible and safe manner. What would be worrisome would be if any PC and chemically obsessive individual or authority could make a claim against the prints, and thus be able to cast aspirations or right out ban public use and sale. The C word is very dangerous.

So what your are saying is that the initial pre-exposure sensitization would load the print with 0.4-08 gram of dichromate. This amount is evenly distributed throughout the gelatine layer? Or on a the surface? The Chromium then hardens the gelatine by a cross binding in the photo chemical reaction, proportional to total illumination received. On development the non hardened gelatine is washed away, presumably with the chromium that has not bound to the gelatine. If not developed the chromium will continue to crossbind to the gelatine even in the absence of light.

So the development bath will contain dichromate, right? Say an average scene has 50 % illumination. Then 0.2-0.4 gram of dichromate would be in the developer (water). If the developer is 1 liter in volume you would have about 300 ppm concentration in the developer. You would have a total of 0.3 gram of dichromate cross bound in the gelatine and thus in the print. The bound dichromate is not toxic? Can it revert to non bound if the print becomes wet for instance?

Sorry to be nerdy about this….. I am definitely not trying to ginn up problems. But carbon printing is too important a process to find ourselves blindsided. Clearly research should continue to find even safer sensitizers.

Chromium compound toxicology……. warning….not nice reading

http://digitalfire.com/4sight/hazard...ology_330.html

/gth

To address another concern mentioned by the OP, carbon prints would not normally contain any dichromate after processing. During processing some dichromate leeches into the fiber of paper prints but this is normally removed by soaking the print for a few minutes in a solution of sodium or potassium bisulfite/metabisulfite.

Sandy

[grzybu]

Chomium(VI) from dichromate is converted into chromium(III) after exposure and only this one will be say with hardened gelatin on the print.
Unexposed chromium(VI) will go to developing batch.
I'm using nitryl gloves for soaking and developing and I don't feel scared by chromium at all.
I remember 20 years ago in school nobody cared too much about dichromates.
Of course it can cause injures to your skin if you leave it there and be dangerous if you breathe dust, but wearing gloves and being sane should keep you safe.
Bad news about banning dichromates, but I've recently found another 1kg jar with PD in my garage so I won't need more in my life