P&P Workflow #11: Cyanotype with Gum Bichromate

October 25, 2007 in Photography, Photoshop, Tutorials

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The following explains the gum process of printing by guest blogger Jim Larimer of PHOTOBLOG by Jim Larimer. Recently Jim put together one of the shots from Kim and my wedding using his gum bichromate printing process and I have asked him to report back on the steps he uses to create such interesting products. Thanks, Jim, for sharing this process with us and for the great work you’ve done for us!

CYANOTYPE WITH GUM BICHROMATE
These two processes represent the very earliest forms of photography. Both were developed in the mid 1800’s and continue to be used even today. Cyanotype is the process that is used in the making of blueprints, but is still used by many Alternative Process printers as their process of choice. And, although it fell out of favor at the turn of the century, the Gum Bichromate process is still used by Alternative Process printers as well.

I chose to combine these processes for making a print from a photo taken recently at Kim and Jason’s wedding. Once I received the digital image, which was 240 DPI, I resized it to 9.75 inches by about 6.75 inches. I let the 9.75 dimension determine the width in CS2. Normally at this point I would make whatever adjustments I felt were necessary to improve the photo using all of the tools available in Photoshop, but in this case the image came looking quite nice (a tribute to Kim and Jason’s photographer!). I did bump up the saturation a little bit as the process that I use needs this extra help.

Now that I am happy with how this looks as a RGB image I go into “channels” then I “split the channels”. Now I have three color separated black and white images each onerepresenting either the blue, red or yellow colors of the original photograph. It is these separated channels that I will you to make digital negatives for the final print.Selecting the cascaded images beginning with the one on top I go to “image” then “adjust” then “invert”. Now I have a reversed image which can be printed as a negative. I go to “file” then “new” and create a new file which is 8.5 x 11 with a transparent background, RGB color space and 240 DPI. Now I use the “move” tool to drag and drop this first negative onto the new file. I position it keeping in mind each of the following negatives will need to be positioned exactly the same when I do them. This is important in the printing process for registration of the negatives. After I have positioned the image I find a space near the edge of the transparent area and use the “T” function to type in the letter of the separation I am creating. R, G or B. Now save, and go on to the next separation and repeat the above steps. For this print of Kim and Jason I saved my RGB separations to a disk and went to Office Max and had B/W overhead transparencies made…now I have negatives!

To begin printing I soak a 9 x 11 sheet of Canson Montval WC paper in hot water for 30-45 mins and let hang dry. I center the “R” neg on the paper and use a hard leaded pencil to mark the edges of the transparency to provide guides for registration. Next I use the same lead to mark the corners of the image on the paper. This gives me reference points for applying the UV sensitive solutions. I mix the Cyanotype chemicals and apply them to this area with a 1″ watercolor wash brush in an area free of sun light, but lighted with a 60 watt household bulb. I hang and let dry in the same light. I place the “R” negative in its registration marks and put this in a contact printing frame. I expose this for 6-7 min in the sun (Denver is quick!) remove and place, image side down, in a sink of warm to hot water for 4-5 min. I then remove and hang to dry. Any kind of light is ok at this point.

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After the print is dry, I return to the 60 watt bulb room and coat the paper, using the same watercolor brush, with Gum Arabic and Ammonium Dichromate mixed with a small amount of Alizarin Crimson tube watercolor pigment. I Let dry in the same light conditions, register the negative and place in the contact printing frame and I expose this print 2 min in direct sunlight (Again, Denver light). Then I place image side down in water for 5 min. At the end of 5 min, I drain the water, refill and continue to soak for 20 more min. Then hang to dry.

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I repeat this process using the Gum chemicals mixed with Lemon Yellow tube watercolors and the print is done!

The final print, when dry, is ready to mat, frame and hang. This non-silver process print will stay permanent for 150 years plus!

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