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.

Exhibition at Atelier pH7

Posted by on 03 Oct 2010 | Tagged as: Uncategorized

Project Vedos is showing some of their work at Atelier pH7, Brussels, Belgium, in October – November 2010.

More Plant Prints

Posted by on 07 Sep 2010 | Tagged as: Anthotype

The summer’s last anthotypes — the exposure has been on for weeks now…

For contact printing I have used cheap picture frames (with non-uv glass) — lightweight and carefree to use. The paper I used here was Guarro Casas.

Jalo Porkkala: Vevey, anthotype.

This plant juice was extracted from petals of (to me unknown) daisy-like orange-red garden flower, the paper was double coated.

Jalo Porkkala: Free Flight, anthotype.

Bird Cherry berries were used as the sensitizer, double coating.

Exposure Time: One Summer

Posted by on 06 Sep 2010 | Tagged as: Anthotype

I have just unloaded two of my split-back contact printing frames and taken out the anthotypes that have been exposed for about a whole Finnish summer. In these northern latitudes UV light seldom is very powerful, so the exposure times for such a slow process can be very long (The Lily of the Valley is an exception, see the previous post)…

Here is a little history of an anthotype print of mine — a picture of a lion statue. The exposure was started on June 1st. Onion skin was boiled for a few minutes, and the tinted water was then used as the sensitizer. The color of the coated paper was quite weak orange-yellow, although I coated the paper four times, with drying in between the coatings. The color was weaker still after exposing for a month.  My contact (positive) inkjet film for the exposure was very contrasty and dense in the shadows.

After a 5 weeks exposure in sunlight (several hours every day, weather permitting) the image was there, but it was hopelessly pale.

I decided to continue printing on top of this pale image with a stronger color, and mashed red rose petals into pulp, and added a milliliter or two of denatured alcohol.

Crushing rose petals.

I then squeezed the juice out of the pulp through a coffee filter, and double coated with the rose purple over the yellow onion image. Before coating I had pushed pins through the film and the paper in all four corners to maintain the registration later.

Two layers of nice rose magenta spread on a sheet of paper.

I continued the exposure with the same negative — couldn’t see the image behind the rose color, but I could register the film to the pushpin holes. I stopped the exposure yesterday because of the low levels of autumn UV light. So the exposure has been continued with the rose color for about 9 weeks now, in addition to the 5 weeks with the onion hue. The print could stand even more, so the highlights could be lightened more. However, the print seems to fade all over during the exposure, even the deepest shadows don’t keep their original color.

Jalo Porkkala: Lion Statue, anthotype.

Here’s another colorant, extracted from mountain cornflower which donates deep ultramarine-like blue juice.

Mountain cornflower (Centauria Montana)

The cornflower is not too juicy, additional alcohol was needed. The sensitizer was coated on paper in four separate layers, but still it wasn’t easy to get an even coating…

The sensitized cornflower anthotype paper and the positive film.

The exposure time finally came to be about 12 weeks…

Jalo Porkkala: Lacock, anthotype.

Got two more anthotype prints coming out from the contact frames on the next few days… will post how they look.

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