Diazo-Sensitized Carbon Transfer

[holmburgers]

Nadeau does talk about carbro in History and Practice of Carbon Processes, as does Friedman in History of Color Photography (probably my favorite book...). A whole chapter in each book is devoted to it.

Here's what Nadeau says:

The Chemical reactions which take place between the sensitized pigment and the bromide print are rather complicated but may be summarized as follows:

1. The ferricyanide oxidizes the silver in the bromide print and so loses oxygen and is reduced to ferrocyanide.

2. The chromic acid oxidizes the ferrocyanide and in doing so forms chromium salts which are capable of tanning the gelatine.

3. The chromium salts, which must be soluble, diffuse back into the gelatine pigment layer and tan the gelatine. Pure chromic acid would only tan the gelatine emulsion layer of the bromide print but would not diffuse back into the pigment.

I'm sure Friedman has a lot more on it as well.

In other news, Kees, is the price from China competitive? Bob, I understand you might be coming to Rochester in January; let's talk about carbro sometime and see what we can see.

 

[CMB]

This description of the carbro chemical reactions is not completely accurate as its fails to account for the function of dichromate - (and whether DAS #3 could be used in place of dichromate was questioned).


The Basic Carbro Chemical actions:


1. The ferricyanide and bromide react on the silver image, resulting in the formation of silver bromide and potassium ferrocyanide.


2. The water soluble potassium ferrocyanide passes into the carbon tissue and reduces the dichromate in the carbon tissue - it is this reduction of dichromate in the presence of gelatin that results in the insolubilization of the gelatin.


See Charles Lighton's discussion in the August, 1927 Photographic Journal for a more complete description.




Charles

 

[holmburgers]

Thanks Charles, that is interesting. With that same logic, is it possible for us to say that blank chemical will reduce DAS and tan the gelatin?

By the way, this DAS acronym is a life saver...

 

[CMB]

Yes, thats the point: Can DAS be chemically "activated" (I don't know if "reduced" is the correct word) to tan gelatin? We know that this happens when it is exposed to actinic light.

BTW: i have recently learned that DAS (thanks to Kees for the acronym) works well in place of dichromate in the albumen adhesion formulation.

 

[holmburgers]

BTW: i have recently learned that DAS (thanks to Kees for the acronym) works well in place of dichromate in the albumen adhesion formulation.

*thumbs up*

I recall that question being posed a while back; a welcome answer for anyone interested in DAS...

 

[keesbran]

In other news, Kees, is the price from China competitive?

Yes it is, about $0,37 per gram plus shipping, minimum order 1 kg. This is about double the price of the Secant offer you had, for the group buy, but I was interested in finding a seller that actually produces DAS and can garanty (some) continuety at a reasonable price. The DAS I got came from a 20kg batch produced end august. I have tested it and is is working as it should.

BTW: i have recently learned that DAS (thanks to Kees for the acronym) works well in place of dichromate in the albumen adhesion formulation.

This is excellent news. I did not have the time to try it myself yet. At what concentration it was used?
By the way: the real credit for the acronym is for my chinese contact!

 

[CMB]

Albumen Substratum

The amount of DAS used in the albumen coating was the same as is used for dichromate: (10g/600mlH20+egg). Its possible that a lower concentration would work as well. FYI, here's the old UltraStable process instructions for the Albumen Substratum:

"1. Take white of one egg, beat to froth and add 450 ML cold tap water. Dissolve 10 grams pot. bichromate (now DAS) in 150 ML warm water and add to egg and water. Mix well. Powdered egg albumen may be used instead of white of egg. Use 15 grams to 450 ML cold water. This solution stored in dark bottle can be used repeatedly. Refrigerate if possible.


2. PET Sheet is immersed in albumen solution approximately 1 minute, then hung to drain. It is then immersed in tray of cold water, shaken for a couple of seconds to clear off excess albumen solution, then hung to dry. Drying may be accelerated with heat. Prior to use it is exposed to strong UV source (exposure unit) for 30-60 seconds to make the thin, invisible layer of albumen insoluble. It is now ready for use and is virtually frill-proof."

 

[VesaL]

Dumb question from the newbie:
Do you have to soak or wet albumen coated film before you mate it with tissue?

-Vesa

 

[keesbran]

Dumb question from the newbie:
Do you have to soak or wet albumen coated film before you mate it with tissue?

-Vesa

just a short 10 second soak is enough

kees

 

[holmburgers]

(there was a url link here which no longer exists)

Time to get the word out! The group buy is going forward and orders need to be in by January 27th.

Cheers everybody; hope everyone's well.

 

[keesbran]

I am looking forward hearing from the DAS group-buyers about their experiences with the magic powder. I am using it also with caseïn now and this works very well! Tonal range looks (a lot) longer that with normal dichromated casein.

kees

 

[BenjaminAustin]

Hi Kees,

Are you referring to caseïn/DAS prints as in an alternative to Gum/Dichromate prints here?

I'm yet to start mine, but before I do I'm also keen to hear of everyone else's experiences.

I'm hoping my negatives will look ok with the longer tonal range (some are 1100mm tall and are very expensive to output)

What is your opinion about the idea of using a spray gun to lay down pigment layers considering the lowered toxicity of Caseïn/DAS emulsion?

Benjamin

 

[keesbran]

Hello Benjamin,

Yes I do refer to casein/DAS as a gum/dichromate replacement. Casein printing has a lot in common with gum. With DAS, printing is very straight forward. Developing a DAS/CAS print is ultra fast! My gum negatives are too flat for DAS/casein but that might be corrected by cutting down the casein/DAS ratio. Now I am using a 8% (powdered) casein solution, with 2% ammonium carbonate and 1 gram DAS (1%) per 100ml. This is a higher colloïd/ DAS ratio than I am using in carbon printing. I will test if I can cut that in half and see what that does with the tonal range.

A spray gun might work. It would be interesting to have such a coating option, because brush coating casein is somewhat more difficult than gum. And for both techniques, coating large surfaces is not evident. But be careful, any toxicity of DAS has never been discribed, but this might be due to the fact that there has not been much research in this respect. But with the knowledge we have it would be much much safer than spraying dichromates.


Kees

 

[chrisaisenbrey]

I think it is time to reanimate this old fantastic thread:

Diazo/DAS is also used replace dichromate in Collotype:

http://www.phototypie.fr/wordpress/...te-photosensible/phototypie-sans-bichromates/

The side contains a nice description about Collotype.

For the carbon print: I tried for long time to sensitize coated gelatin layers with a brush. This works in principle even with the Speedball sensitizer. However I always get some degree of fog. (Even on the unexposed parts of the gelatin layer). So I add the DAS now to the gelatin before coating.

Many thanks to Chris for making the DAS available. Since I’ve access to a photo spectrometer I made some absorption spectrum of DAS in water. It has a maximum around 333nm.

 

[keesbran]

I think it is time to reanimate this old fantastic thread:

Diazo/DAS is also used replace dichromate in Collotype

Since I’ve access to a photo spectrometer I made some absorption spectrum of DAS in water. It has a maximum around 333nm.

Hi,

This is very good news! And your site is very impressive too. Did you observe sensitivety differences or the need to adapt your negatives with DAS compared to dichromate?
And thanks for the spectrometer data.

Kees

 

[chrisaisenbrey]

Hi,

This is very good news! And your site is very impressive too. Did you observe sensitivety differences or the need to adapt your negatives with DAS compared to dichromate?
And thanks for the spectrometer data.

Kees

Hello Kees,

The collotype is not my work. (But I would like to try the process) So I don’t know how they have to adapt the process.

For carbon print:
I changed too many parameters to directly compare the results with DAS and dichromate. (I’m still on my way to learn the process of carbon printing)
The sensitivity changes a little but the exposure time is in the range of some minutes with my “face tanner” UV light (~50cm distance).
I have the impression that DAS is working a little softer, but I might be wrong. The gamma can be influenced by the amount of DAS (as reported before) and also by the amount of pigment. I think the gamma should be directly proportional to the amount of pigment. With high amount of pigment it gets of cause difficult to distribute it equally in the glop. (I start with glycerin/pigment/some water and use a glass muller).

For a formula like this:

500mg lamp black (Kremer pigments 47250 Flammruß)
~1ml glycerin
~1g sugar
35ml water
150mg DAS (in 5ml water)

on 17cmx25cm Paper

I get a gamma of 0.7-0.8 on a transparent support. That should lead to a reflective gamma (on a paper support) of about 1.5. So it is in the range of silver-gelatin paper.

Chris

 

[yashasvi bhuta]

http://www.sigmaaldrich.com/catalog/product/fluka/33483?lang=en&region=IN

can this product be used

 

[holmburgers]

http://www.sigmaaldrich.com/catalog/product/fluka/33483?lang=en&region=IN

can this product be used

Yes, that is the same material; CAS 2718-90-3

 

[chrisaisenbrey]

source for DAS/ Diazo

Here is a European source for DAS/ Diazo :

Dead Link Removed

I have no relation to the shop except of being their client and being a fan of their webpage about collotype (http://www.phototypie.fr/wordpress/en/visite-guidee-phototypie/ )

 

[holmburgers]

Here is a European source for DAS/ Diazo :

Dead Link Removed

Not a bad price at $1.31/gram.

I couldn't help but notice that they've taken my pamphlet, translated it into French and put it on their website.

I've been duped... I sold it so low that others are able to make a profit reselling it! And plagiarised to boot, but in another language, so I guess that's kinda cool...



Ay yay yay

 

[Photo Engineer]

Pauvre Chris. Tsk.

 

[Michel Momal]

Hello,
you should not have such feelings.
The DAS that is for sale on the site does not have the same origin. I still hold almost all of the 160 gr of group purchasing.
Moreover it is more pure (97%). I had a lot of trouble getting the new stock and the purchase price actually is very supperior to that of group purchasing, and there will be no profit probably on this sale.
I still obviously in the idea of ​​promoting this alternative dichromate.
Indeed, I took the information that was given, but they should be familiar to users because they are essential to understanding its use.
I should not publish them ?
However, I added the result of my long work on the use of the DAS for collotype with the use of hydrogen peroxide instead of permanganate which can also serve enthusiasts of other processes.
There are in addition a safety data sheet.
They are available for all and can be disclosed.
I hope I have reassured you

 

[holmburgers]

Hi Michel,

I didn't know that you were responsible for the DAS on sale at Phototypie. Honestly, it does not bother me at all, and thank you for clarifying that this material comes from a different source. As for using my pamphlet, again, I am more flattered than anything and don't really harbor any ill feelings about it. I'm glad you clarified the situation though; it's nice to know.

Anything that promotes the use of DAS is good in my book.

 

[holmburgers]

Pauvre Chris. Tsk.

I'm so poor, I ship packages filled with helium so that the post office will pay ME!

 

[chrisaisenbrey]

Oh, well I caused a little confusion with my post here. But with some happy end

But I reactivated the thread about diazo! I hope this will promote the use of diazo for a green carbon printing. It is such a magic process when the physical picture is swimming as a relief in the warm water.


Michel your work on collotype is just fantastic. I would like to try this process myself.

But at the moment I’m still busy with improving carbon printing. At the moment I try to go for color carbon.