x-ray film sheets for DCG?

holo_cyware · Post by **holo_cyware** » Wed Dec 03, 2008 4:48 pm

It just occured to me that the x-ray sheets may be used for DCG once we get rid of the original silver halides (a simple bath of an unused sheet in thiosulfate should do it). I may be reinventing the wheel here.
We'd be left with a nice gelatin layer similar to the film sold by ORWO; just a nice clean gelatin layer waiting a dicromate bath (or why not, a new silver halide + a dye sensitizing bath) à la Jeff B. method.

Do you think this could be feasable?

Colin Kaminski · Post by **Colin Kaminski** » Wed Dec 03, 2008 5:14 pm

As long as the film is not birefringent it should work fine.

Hans · Post by **Hans** » Wed Dec 03, 2008 9:17 pm

I think that you can do both. But is x-ray film cheaper than Orwo? Why not just coat your own plates. Once you have done a few it is not so difficult anymore and it is by far the least expensive method. Here is a coating technique that gives near perfect coatings every time:

Glass plates need to be cleaned thoroughly before coating and in case of silver halide emulsions it is preferable to pre-treat the glass with silane.

1] Place a flat marble stone or a flat metal plate in the fridge.
2] Mix a solution of 2% gelatin in water.
3] Take your flat surface from the fridge and place it perfectly horizontal.
4] Put some sheets of paper on top of your cold flat surface.
5] Heat your glass plate with a hair drier.
6] Put the glass plate on top of the paper.
7] Pour the gelatin onto the glass and spread it evenly over the glass.
8] Pull the paper from between the glass and the cold surface. This allows the gelatin to set quickly.
9] After the gelatin has gelled (this will happen within minutes), place it in a dust free place to dry.

Using this method there is virtually no limit to the size of your coated glass plate and it does not waste as much gelatin as with the mold coating method or the Victorian curtain method. Also, there is no need for a Meyer bar.

holo_cyware · Post by **holo_cyware** » Thu Dec 04, 2008 7:29 am

Well, x-ray film is waaay cheaper than the ORWO one because I can get it for free

More questions:

1. Is it possible to clean the gelatine from an exposed and fixed x-ray film? By cleaning I mean getting rid of the left silver and whatever can be in the gelatin, leaving the gelatin intact.

2. This one is for Jeff B. Nobody seemed to notice, but at some point, you mentioned the fact that by dehydrating a DCG hologram to extreme levels (the alcohol bath being just the first step, and the last one involving a strong dessicant such as calcium chloride in a dessicator for a week) the hologram became immune to humidity for years. It seems that the gelatine must have changed it's structure to a point where it wouldn't absorbe water from air. You also said that years after you dumped the plate in water and that eventually ruined it, but the air didn't do any harm. If I didn't dream that, it would be something really nice.
Can you detail a bit? Maybe someone could put the link to the thread, as I can't find it anymore.

3. The fancy a-skull-hologram-on-glasses-lens kind of items are supposedly DCG holograms. If so, does anyone knows exactly how are they waterproofed?

JohnFP · Post by **JohnFP** » Thu Dec 04, 2008 1:24 pm

the more moisture that is taken out of the emulsion, the more crosslinking there is (even in unexposed regions) and the more insoluble the emulsion is. When taken below 2% water content the emulsion is insoluble at room temperature due to being fully crosslinked.

http://www.holowiki.com/index.php/The_M ... CG_Process
http://albumen.stanford.edu/library/c20/kozlov1983.html

I still have many DCG holograms that I dried conventionally with Alcohol and a hair dryer and they still have not disappeared even with no cover or sealing. Some are over 5 years old. They have been subject to hot humid Mid Atlantic (Maryland, USA) summers and cold dry winters. These are my rejects.

To insure the longevity of the "good" holograms I use an inexpensive method of sealing the hologram from the envionment. I use 3 minute epoxy around a cleaned 5mm border on the hologram with another piece of clean glass to make and O-ring type seal.

Most professional use an indexing matching UV epoxy and cover the entire emulsion surface, then they add the top cover glass. In this method you want to still remove a small edge of emulsion around the edge of the hologram to insure you have a glass-epoxy-glass interface and not a glass-epoxy-emulsion-glass interface in which in the latter, the moisture can penetrate the seal by being absorbed into the exposed gelating edge.

Ed Wesly · Post by **Ed Wesly** » Thu Dec 04, 2008 10:53 pm

Yes, it is possible to fix in just sodium thiosulfate to remove the silver halides and start with a fresh gelatin layer. Many papers had been written in the early years about doing just that with Kodak 649-F plates. I used a recipe for deriving the layer from Agfa plates, and I am not home so I can't cite it. The basic operation was fix, wash well in warm water, sensitize, expose then process. So you are on the right track. However these images weren't all that bright, as the layer was only 5 microns or so thick after fixing.

A curious thing about X-Ray films is that they are coated on both sides! This might be an interesting experiment!

Colin Kaminski · Post by **Colin Kaminski** » Sun Dec 07, 2008 12:43 am

I would think the film would potato chip when drying.

holo_cyware · Post by **holo_cyware** » Sun Dec 07, 2008 12:59 am

I'm going to try it, and let you all know how it went.