And, I might add, that the coatings are far far simpler than Kodachrome! We handcoated Ilfochrome in our lab at EK, at least a serviceable example. If we had continued it would have been fully functional as we hit it pretty much right on, first try.
Wow, hand coating Ilfochrome .... can you give us any indication whether the chemistry involved in this is obtainable by random home brewers? Is this something we could remotely consider doing once we run out of materials?
I have given the entire process sequence elsewhere here. Right now, I am tied up with a workshop and cannot dig out the information. Sorry. I cannot even find the original single layer strips that I made to show feasibility. One was damaged and I had planned to make another set.
I've spent some time searching for Ilfochrome recipes on APUG and here is what I found so far:
- I found this thread where a lot of chemistry is thrown around. Unfortunately brookse never posted a specific recipe, but he seems to have one.
- Here is a thread with some more info and a recipe which is said to work poorly.
- Here is another thread with a recipe. And another one. And one more.
- A number of threads recommend Dr. Beers developer to replace the Ilfochrome dev. Here is the recipe.
- Following the advice in these threads I searched for "dye bleach ciba patent" and boom, a long list of patents (like this one and that one from EK) describing dye bleaches and referencing other patents on that topic.
A long list of odd ball (to me) chemistry is mentioned but some are obtainable from Sigma Aldrich: 2,3-Dimethylquinoxaline, 2-hydroxy-3,6,7-trimethylquinoxaline, Sodium 3-nitrobenzenesulfonate, Phenazine, Quinoline and N,N-Dimethyl-4-nitrosoaniline.
All of the exotic catalysts will work. The 2, 3 Dimethyl quinoxaline is what Ilford uses AFAIK. I am intending to design my color material (If I ever go it) around Phenazine probably. IDK.
All of the above are rather toxic and should be handled carefully and all DB bleaches are similar. They are about pH 1 or so, have HCl or H2SO4 in them, Thiourea, NH4Br, and other things. Recent DB bleaches use Sulfamic Acid with the same low pH.
You must used a support such as YUPO or RC, as the bleach destroys most papers.
The MSDS and many other descriptions I found online claim that 2,3,6-trimethyl-quinoxaline are used by Ilford. This substance, however, seems to be difficult to get, at least Sigma Aldrich doesn't seem to carry it. The Ciba patent mentions that very good results are obtained if a mix of two catalysts are used which have different redox potential, and based on that patent a combo of 2,3-dimethyl-quinoxaline and 2-hydroxy-3,6,7-trimethylquinoxaline could be very promising. I have, unfortunately not delved into this deeply enough, but the Ciba patent does mention patents which could provide useful recipes.
About paper support: could bleached and fixed b&w paper do the job? I have tons of b&w prints that only highlight my poor photographic skills which could be repurposed for this.
Someone has described elsewhere on APUG, how these quinoxalines may be easily made by simpler chemicals. Unfortunately, the scheme uses p-Phenylene Diamines and the real synthesis uses o-Phenylene Diamines. Mix the right one with Diacetyl, and in one step you have the Quinoxlaine. Easy one step.
Not explosive, nor very corrosive.
FB papers are not a good idea here. RC would work.
Since I can get quinoxaline and some variations of it at reasonable cost (compared to cost of Ilfochrome paper and given that it is used only in small amounts), I think I will just plunk down money for the real thing.
Here is my home brew strategy:
- Replace Ilfochrome fixer with OlepH 6.5, which is based on Ole's quick fix but has pH adjusted to 6.5
- Replace developer with Dr. Beer's developer and make sure that color balance can be restored. Experiment with different contrasts.
- Once this is all figured out, play with dye bleach. I guess I'll start with sulfamic acid for pH of 1, various amounts of 2,3-dimethyl-quinoxaline and 2-hydroxy-3,6,7-trimethylquinoxaline and 50g/l of NH4Br. You also list thiourea, can you tell me what that is supposed to do in the dye bleach?
One thing which honestly surprises me about the process is the extremely relaxed attitude towards fixing. Although it is supposedly archival, they use sodium thiosulfate for two minutes without much fuss, compare this to the complex procedure recommended even for plain b&w RC paper!
Thiourea is a fixing agent that helps accelerate the dye bleach reaction.
Since the "paper" is really plastic, the wash will proceed rapidly in the fully swollen emulsion. But, be careful. There are known cases of browning of Dye Transfer prints due to under fixing and/or under washing.
I do not recommend storing chromogenic and dye bleach prints together. You will notice a strong odor from the dye bleach prints after a few years. IDK what the reason is.
Any hints about recommended concentration of thiourea in such a dye bleach?
Originally Posted by Photo Engineer