November 2010

Monthly Archive

Return To Gum, Part 3

Posted by on 21 Nov 2010 | Tagged as: Gum Bichromate

Printing the first layer of 4-color gum print on a paper attached to aluminum.

Mixing the the sensitizer for the first gum layer. There will be 3 ml of the stock pigment + 6 ml gum + 4 ml distilled water + 4 ml potassium dichromate 13% + Tween 20 1:3 2 drops — that makes 17 ml of the sensitizer in total, for a 26 by 42 cm print.

Coating the paper with the first pigment layer, ivory black in this case.

Registering and taping down the negative for the black layer.

Exposing in a vacuum frame of a plateburner.

Developing the print in water after the exposure.

The first layer (ivory black) of the gum print.

Return To Gum, Part 2

Posted by on 20 Nov 2010 | Tagged as: Gum Bichromate

Part 2 of the series of making a 4-color gum print on Fabriano Artistico paper, glued on a sheet of aluminium. This part describes the making of color separation negatives and registering them with the substrate.

An Oklahoman landscape, the original digital image going to be printed in gum. The image has been sharpened a bit, and the color saturation slightly increased.

Printing the four color separation negatives with an Epson 3880.

It is fun to use different kinds of “incorrect” methods for color separation. Here I split the RGB color channels to grayscale images, and inverted them to negatives for printing CMY gum layers, respectively. The fourth channel is black, which is a grayscale channel mix from the RGB image.

A piece of clear film is taped to one end of the negative. This extra length is later used for registering purposes.

Stacking and taping the negatives together on a light table.

Trimming the stack edge.

Punching registering holes to the stack of the four films. The aluminium sheet is punched in the same way.

Putting the substrate and one of the unstacked negatives to the registration pins…

…and drawing with pencil the area to be sensitized.

Return To Gum, Part 1

Posted by on 17 Nov 2010 | Tagged as: Gum Bichromate

One more experiment with the gum printing before the end of the year, and setting the project to rest. This time I was interested in trying to glue the paper to a firm base, to prevent it from shrinking between the wet processes, so that perfect registration of colour layers could be achieved. I used aluminium as the base, because there is a local printing house selling used aluminium offset sheets cheap.

The back of the aluminium offset sheet looks perfect for attaching the paper to…

…but first it must be sanded and cleaned well for the glue to adhere. No need to make it beautiful… it will be covered by the paper.

Rinsing off the sanding dust.

Drying and cleaning with a paper towel.

Coating the back of the paper (Fabriano Artistico Extra White) with diluted PVAc adhesive.

Laying down the paper (with adhesive) on the cleaned aluminium.

Covering the sheet with protective paper and pressing with a roller for good adhesion.

Covering with thick cardboard and using jugs of water as weights.

After the sheet had dried overnight the edges were trimmed. Extra sizing was done using Caparol Binder diluted 1:8 with water.

Mixing the stock colors: Two 5 ml tubes of Schmincke watercolour mixed with 40 ml gum arabic (Varn 14 BĂ©).

My set for 4-color gum printing: Ivory black, permanent carmine, phthalo blue, and cadmium yellow light.

BTW, all these pictures are stills from my pocket HD video cam, which was set up on a lightweight tripod… I carried the camera around while working and set it up to record the making of a 4-color gum print mounted on a sheet of aluminium. When I get the video edited I will put it online too…

Mitone MITV100 HD Camcorder.