Wednesday, December 1, 2010

Diffusion Transfer Reversal

Diffusion Transfer Reversal, or DTR, is possibly the most important photographic process developed in the 20th Century, and almost certainly an important technology that few have ever heard of, but nearly everyone knows something about.

DTR is the basic process that enables instant photography as practiced by Polaroid, Kodak, Fuji, 20X24, and was a key step in the development of integral films such as now made by The Impossible Project.

Here is a link to more posts about DTR, which was invented before WWII.  And here is a link to the Rott patent. Weyde invented DTR.

Type 55 was just one of many products that depended upon the use of DTR to produce a negative that is processed in such a way as to rapidly produce a transfer of metallic salts onto a receiver, bridged by a developer. The action of DTR is battery-like and DTR kinetics are complex and still being studied today.

I wanted to show some results of DTR that we have produced here. They are early and crude, but show definite ability to use existing films - in this case EFKE 25 - as an emulsion capable of generating a sharp, high tonal gradient DTR image onto suitable receiver paper.

Below is a DTR image produced using EFKE 25, in our own sleeve, and employing 17 year old T55 reagents and paper that was ruined by humidity, which in itself is very instructive. I shot this today in a Speed Graphic with a 545 holder to point out where we need to buy tooling and obtain materials for a new product.

 We know how to make new, fresh reagent, and we now have a very tonally rich emulsion.  We do not now have a supply of receiver paper.  We do have a source of pod-making equipment, and the ability to mass-produce sleeves, inserts, stops, clips and other parts if we can obtain the tooling at a reasonable price.
Here's the scanned EFKE 25 negative, showing less DTR failure, but with very uneven (slightly exaggerated in the scan) development. Note however, that the cleared portions have a tonality that is not too different than the print, which is good. Perhaps this defect is similar to what we saw with Reagent III and the sponge, but with a spread out appearance.
Here's a shot of the sleeve used for the above, and some of the EFKE (here shown in lower case_ PL 25 M.

11 comments:

Bob Crowley said...

The white dots are caused by damage to the receiver paper, and the mottling is caused by long expired reagent.

The negative is also mottled, but has none of the spots. It is very sharp and the overall density is about right! So is the print!

awldune said...

Looks very good to me! I wonder if you could steal receiver paper from Fuji instants to experiment with?

Bob Crowley said...

Beauty is in the eye of the beholder. Old Pol used metal sulfides to produce the black we see as the positive. Fuji uses organic mercaptans in conjunction with nuclei.

I should try it, though the receiver sheets are completely different. I ought to swipe the Fuji pod as well.

You can tell which is which with bleach: Old Pols don't react with chlorine bleach as that does not break metals. But, bleach does break organic molecules, so any part of a Fuji positive that gets touched by it turns white.

Tricky aren't they? The Fuji process is superior in some ways - it uses so little silver so that saved a lot of money. It also has great amplification so uses finer grained silver and this gives a speed boost, and the layers are thinner, so the sharpness is much higher. Also the mid greys are better delineated with the Fuji FP100B receiver.

But we want to make it synergistic, at least, with the processing of a good silver negative. So metal salts are probably going to be our best bet. Mercaptans smell bad too.

The magic of instant DTR is in the receiver.

Anonymous said...

I really like that first picture. It's so bad it's kind of cool, you should save the original.

Michael said...

Is there any reason that the DTR sheet has to be paper? Would it be possible for it to be on a clear sheet so you would end up with a BW slide and a negative?

Bob Crowley said...

DTR has indeed been done on clear sheets, so in theory, yes! Agfa produced an overhead projector material for a number of years that did that, and Polaroid had monochrome slides, starting in the oldest roll film format.

Michael said...

Put me down for a box of that and a box of the regular. Hope this project really works.

Anonymous said...

Perhaps an odd question, but would it be possible to use, say, photographic paper as the negative material instead of using film? I mean, DTR is just the transfer of undeveloped silver halide, unoxidized developer, and unused alkali to the receiving layer, right? So, light sensitive photographic paper on fixed-out paper could be used to make an image - or am I missing something?

Bob Crowley said...

Yes it certainly can. You need to try putting just a wet blotter paper with a monobath on your photo paper negative and then pull that away and see the positive image that will form from it. It is very easy to do.

Anonymous said...

Oh, that sounds like a very fun thing to try. I don´t really know why, but there is something about the whole instant process that is very fascinating.

Also, that raises another question that that I would like to ask. I have an old Polaroid 150 roll film camera. I was thinking that it might be possible to make a crude assembly of a roll of positive receiving paper and a roll negative paper with pods that one could then use like the old roll film and run through the set of rollers in the camera and then (possibly) end up with an image. Please excuse me if I betray any ignorance, but I was thinking that it would perhaps be an interesting thing for me to try out. Do you think that it would work at all? I mean, the design strikes me as crude, but I got the idea after having looked at a couple of videos on the 20x24 camera, which also seems to use a similar kind of system.

Bob Crowley said...

Do it. Show us the results!