gum printing

Libby Young · Jan 30, 2019

Hi
I am new to gum printing, and I am not managing to get an exposure. I mixed water-based glue with water colours (both pea-sized amounts) with a teaspoon of potassium dichromate (8g diluted in 100ml of water) and painted it on water colour paper (a type I use this successfully for cyanotypes. I waited for it to dry and exposed under bright sunlight for 6-10 min (varying attempts).

I then washed but no image appeared - just the same colour block as before exposure.
Any idea what I could be doing wrong?
Libby

Peltigera · Jan 30, 2019

Are you using a light sensitive glue? Traditionally, gum printing used Gum Arabic which becomes insoluble in water when exposed to light. Not all glues will do that.

Libby Young · Jan 30, 2019

I am not using gum arabic as I was advised that Gloy was fine. I have tried two different types of water based glue. Is the glue supposed to be light sensitive or not?

Libby Young · Jan 30, 2019

Do I need to mix the potassium dichromate with water in darkroom conditions?

Peltigera · Jan 30, 2019

If the glue is not light sensitive you cannot produce an image with light, can you? Strictly, it the mixture of gum and Potassium Bichromate that is light sensitive, but you still need to use the right gum - it needs to be a protein based gum as the process relies on the proteins being tanned to make them insoluble. Has the person who told you that Gloy was fine got any pictures to show you?

Libby Young · Jan 30, 2019

Peltigera said:
If the glue is not light sensitive you cannot produce an image with light, can you? Strictly, it the mixture of gum and Potassium Bichromate that is light sensitive, but you still need to use the right gum - it needs to be a protein based gum as the process relies on the proteins being tanned to make them insoluble. Has the person who told you that Gloy was fine got any pictures to show you?

I have been using Spirits of Salt, a book by Randall Webb and Martin Reed. None of their other instructions have ever let me down. I guess will be have to try gum arabic.

Peltigera · Jan 30, 2019

I have had a quick look on Google and Gloy make a number of products. If you are going to use Gloy, it needs to be the brown liquid which I would have thought would work. The white Gloy paste will not, nor will the Gloy glue sticks.

Libby Young · Jan 30, 2019

I have just seen this suggestion:
Some gum practitioners also substitute a liquid glue (like Gloy®), or albumen, for the gum arabic.
Has anyone had any success with albumen? It would be cheaper than gum arabic

BrianShaw · Jan 30, 2019

Often the best way to learn something new is to start with proven classic methods. After a success it is a lot easier to vary methods or experiment with alternative materials. Learning gum printing is difficult enough... don’t make it so difficult that you don’t succeed.

For me the challenge has been finding the right balance of pigment to gum, the right pigment, the right paper, the right sizing, and the right exposure. And after all that I still often struggle with light images or exposed gum that seems to wash right off the paper.

Herzeleid · Jan 30, 2019

Libby Young said:
I have just seen this suggestion:
Some gum practitioners also substitute a liquid glue (like Gloy®), or albumen, for the gum arabic.
Has anyone had any success with albumen? It would be cheaper than gum arabic

If you mix your own gum arabic solution nothing would be cheaper than that. I buy a kilo of imported Kordofan originated gum arabic around 15 us dollars.
A mixture of 1 part gum powder 3 parts water is usually around 14 baume, at least for the gum that I bought. That would make 4kg gum arabic solution, probably more than 3.6 liters.
Add some preservative like sodium benzoate for shelf life or prepare small amounts as you need.
I usually use a plastic spoon of gum ( ~4-5ml) and spoon of dichromate and some pigments for 8x10" print.

Libby Young · Jan 31, 2019

Herzeleid said:
If you mix your own gum arabic solution nothing would be cheaper than that. I buy a kilo of imported Kordofan originated gum arabic around 15 us dollars.
A mixture of 1 part gum powder 3 parts water is usually around 14 baume, at least for the gum that I bought. That would make 4kg gum arabic solution, probably more than 3.6 liters.
Add some preservative like sodium benzoate for shelf life or prepare small amounts as you need.
I usually use a plastic spoon of gum ( ~4-5ml) and spoon of dichromate and some pigments for 8x10" print.

Sounds like a good idea. I am in Cape Town and gum arabic is hard to come by but I think I have found a source now. So I will try again

gum printing

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