Ammonium Dichromate replacement for Carbon printing

[Struan Gray]

Pete, can you give more detail about the banning of dichromates in carbon printing?

I've had a trawl through the REACH and other EU legislation and can't find anything relevant. The legislation aimed at big industrial users may make dichromates harder to come by, but I don't see anything that will stop the specialist chemical suppliers selling it to carbon printers.

[sanking]

Most of the unreduced dichromate comes out in the mating bath when the exposed and sensitized tissue is mated with the final support. The mating bath can be reused to save water, in fact this is best procedure for carbon printing as old/flat water avoid gases that may be in water fresh from the faucet. My estimate is that about 95% of the unreduced dichromate comes out of the tissue in the mating bath, the rest would come out in warm water development.

The only significant health risk to the carbon printer is inhalation of the dichromate powder when mixing the solutions, and/or ingestion. Both risks are pretty easy to minimize. You also want to wear nitryl gloves to protect your hands from the dilute solution, but here the risk is primaily dermatological as the solutions are so dilute.


Sandy

[Andrew O'Neill]

Great. So now I have to stock up on AD?

[Pete Watkins]

Struan,
I was informed of the oncoming ban by a supplier in London. They let me know the source of their information. It's a part of the UK Health & Safety Executive, a government department. They will be monitering the ban but it is a European directive, pushed out by The EEC. Hopefully it will be reversed if we ever get e vote to leave that organisation.
If you PM me your e-mail address I'll foreward you the e-mail that I recieved from them. If anybody else in EEC countries wants to see it just do the same.
Good news for the rest of the world, unless your government is stupid enough to join the EEC this ban will NOT apply to you.
Pete.

[gth]

Sandy,

Just finished reading the DSA thread on APUG. Thanks for the link.

In your opinion, if one "started from scratch" in developing ones Carbon printing workflow do you see any intrinsic problems in achieving the same results (image quality, print stability etc) with the DSA methods vs traditional AD methods? And if so, can you comment about what areas you would be apprehensive about.

/gth

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

[gth]

DSA available worldwide

http://www.chemicalbook.com/Chemical..._CB9384077.htm

Looks like about $0.60 per 8x10 print?

[sanking]

"In your opinion, if one "started from scratch" in developing ones Carbon printing workflow do you see any intrinsic problems in achieving the same results (image quality, print stability etc) with the DSA methods vs traditional AD methods? And if so, can you comment about what areas you would be apprehensive about."

Since I have not actually established a good work flow with DAS, 4,4'diazidostilbene, I can only speculate. DAS worked very well in the Ultrastable color carbon system but so far as I know it is not currently being used by any of the top monochrome carbon printers. Areas that would concern me are, 1) the low saturation point of DAS, about 3% as I believe, in comparison to about 10% for potassium dichromate, and 30% for ammonium dichromate, 2) the heavy stain that DAS gives to images on paper, making it necessary to use the very powerful oxidizer potassium permaganate as a clearing agent, 3) the reduced sensibility, about a stop from what I have read, compared to dichromate, 4) the light sensitivity and keeping qualities of DAS.

Sandy

[sanking]

DSA available worldwide

http://www.chemicalbook.com/Chemical..._CB9384077.htm

Looks like about $0.60 per 8x10 print?

Sorry, just to point out that I mistakenly called 4,4'diazidostilbene "DSA" in a previous message. That should have been "DAS."

Sandy

[Ed Bray]

As one who is just starting down the Carbon Printing road (and so taken with it I am converting my darkroom to solely Carbon Printing and selling off my four enlargers) I have been buying up stocks of Ammonium Dichromate as they become available (in the UK), I currently have 500 grams of crystals and am hoping to add to that before the EU ban comes fully into place (I say fully as a large number of companies will only sell Ammonium Dichromate to large commercial users or Educational establishments.

On another note, I was printing some tissues on Thursday and I took my gloves off between the sensitising and exposing stages, when I completed the exposure I mated the exposed tissue to the final medium forgetting to put the gloves back on. What made this worse was earlier in the day I managed to cut my finger on one of my mitre trimming knives (whilst making a frame) and although I had a waterproof plaster on I am pretty sure some of the Dichromate laden liquid would have got in. Nothing I can do about it now but a lesson learned.

[gth]

One Exposure is not going to to do you in. It's cronic exposure over time that makes a difference, at least for small doses per exposure. But it's fairly nasty stuff. It does not matter if your have wound or not…. Ammonium dichromate goes straight through your intact skin. You need to protect your skin at all times. Check out...

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

At the bottom of the page they recommend some skin ointments that will keep the dichromate out that you can wear on your hands ( I guess you can wear that inside your gloves), or Zink Oxide ointment in your nose is also good. It IS a carcinogen and it will even mess with your DNA. But it is is chemical and to really affect you health, you have to be subjected to sustained exposure - that's how I read it. But you see some YouTube videos where folks are handling this stuff with bare hands…. not good.

I think you are probably in more danger from being "exposed" having 1 kg of a known strong carcinogen in your house….. that **could** weak havoc with your life in todays world.

And that's where I am coming from …… carbon printing is otherwise squeaky clean…. carbon pigment, gelatine and water + just about the most fabulous printing method there is… if only we could get rid of the dichromate…..

As one who is just starting down the Carbon Printing road (and so taken with it I am converting my darkroom to solely Carbon Printing and selling off my four enlargers) I have been buying up stocks of Ammonium Dichromate as they become available (in the UK), I currently have 500 grams of crystals and am hoping to add to that before the EU ban comes fully into place (I say fully as a large number of companies will only sell Ammonium Dichromate to large commercial users or Educational establishments.

On another note, I was printing some tissues on Thursday and I took my gloves off between the sensitising and exposing stages, when I completed the exposure I mated the exposed tissue to the final medium forgetting to put the gloves back on. What made this worse was earlier in the day I managed to cut my finger on one of my mitre trimming knives (whilst making a frame) and although I had a waterproof plaster on I am pretty sure some of the Dichromate laden liquid would have got in. Nothing I can do about it now but a lesson learned.