Gum Bichromate

[stephen_gray98]

For a three colour print I register all three negatives together visually (having printed registration marks), tape them together over a sheet of paper and then push a tack (or similar) through 3 or 4 points around the negative, making sure the tack goes through all three negatives and into the paper. When you are ready to expose the first colour, place your first negative (say yellow) on the print and push tacks through the holes and then tape the negative down (I use blue printers tape), you can then remove the tacks. Providing you have pre-shrunk the paper then you can line the other negatives up using the small holes in the paper and the negative. As long as the holes are at the edges you won't see them once the print is framed.

SPG

[ropapp]

compressed to make the negative Gum Dichromate is my biggest problem. Determine the curve in Photoshop. What methods have you used?

[TheFlyingCamera]

IF this discussion is going to veer off into making digital negatives for tri-color gum, it needs to move to hybridphoto.com.

[GumPhoto]

IF this discussion is going to veer off into making digital negatives for tri-color gum, it needs to move to hybridphoto.com.

oh jeeze...

[ropapp]

grateful for the indication
hug
rodolfo

[vintagepics]

IF this discussion is going to veer off into making digital negatives for tri-color gum, it needs to move to hybridphoto.com.

I have a Beseler Dichro enlarger with the c m y filters. I am open for any suggestions other then making digital negatives for this process. Im all ears.

[GumPhoto]

I have a Beseler Dichro enlarger with the c m y filters. I am open for any suggestions other then making digital negatives for this process. Im all ears.

For many years, my process involved enlarging b&w negatives (usually 120) onto lith film, which I then developed in very low-contrast developer to produce 5x7 positives. The positives were, in turn, enlarged onto lith film to make the negatives used for the gum photos - anywhere from 16 to 36 inches. It is a fairly straightforward process.

Lith film is obviously not sensitive to red light, so for color separations I used sheet film to make inter negatives from color transparencies. 5x7 Super XX was my favorite, but anything will do. Its a little more complicated because the work has to be done in total darkness while maintaining exact registration as the three separations were made through the C, M and Y gels. I used a small 5x7 speed easel (similar to the ones now made by Ganz) and screwed it down under the enlarger so that it could not move. As 5x7 was too small, I had to go thru the process of contacting printing them to lith to make the positives that could be enlarged in a manner similar to that described above. It is a long and painful process, but perfectly viable to anyone that eschews digital means.

[michael9793]

go to youtube and type in tri color gum printing and there is a good 4 part series and really gives you a visual on it. that is what i did and then supplement it with article from alternativephoto website.

[michael9793]

IF this discussion is going to veer off into making digital negatives for tri-color gum, it needs to move to hybridphoto.com.

I'm very strong about that fact that if any digital stuff is going to be talked about, it should go to the other website. BUT with the lack of separation films available I think there is a time to talk about using computers to help us make our analog work work. In my situation it is the only way to keep my analog work grow to new areas. I don't feel that I'm straying into the dark world of digital. We need to have a little give and take here. Just my thought.