# Thinking about trying Gum Bichromate



## hughesdih (Nov 22, 2007)

I've been doing a little reading on the subject and I had a few ideas I wanted to get some feedback on before I try. The first is, since its a negative process if I wanted to make it directly into a positive could I mix it with white pigment and coat it on black paper? Or use white pigment and coat it on glass which I would paint the back of it black? Which brings me to my second question. Is it possible or practical to use glass instead of paper for this process? How about metal? If so is there something different I need to do to? Any advice is much appreciated. Thanks
David


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## terri (Nov 22, 2007)

Welcome to TPF! We have a gum printer on board here, Windrivermaiden, who does lovely work. She has posted several of her images here in the Alt forum; scroll down and check them out. I believe she also put up a basic tutorial of sorts. 

At any rate, hang around with us; she'll be online soon to help you out.


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## hughesdih (Nov 23, 2007)

Thanks Terri. I can't wait. I saw some of her stuff; it looks great. I think the alternative processes are great. I can't wait to jump in and have some fun with them.


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## terri (Nov 23, 2007)

hughesdih said:


> Thanks Terri. I can't wait. I saw some of her stuff; it looks great. I think the alternative processes are great. I can't wait to jump in and have some fun with them.


You've come to the right place, then!


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## windrivermaiden (Dec 5, 2007)

Here I am! I have been slaving away with that "real life" stuff that takes me from my passions...

First let me explain...in gum-dichromate printing, your negatives are Negatives...so, what they expose on to the emulsion is the positive image. The UV light goes through the clear(er) parts of the negative and hardens the gum Arabic via a chemical reaction with the dichromate,..And the negative image, which isn't exposed, remains water-soluble and is washed away in the water baths..., leaving a positive image.

That being said. To get a negative image in white, one must start with an inter-positive if using litho-film or make a "positive" transparency using digital processing methods.

There is another gum/dichromate process which is called GUM OIL printing which is the same process using "Positive" and un-pigmented emulsion which is exposed, washed and dried and then rubbed with oil color to reveal the positive image in a resist type method. I think I posted an example here somewhere..."Castle in the Sky"

My experience with white pigment is not great...I tried a few experiments with Sennelier watercolor pigment. Chinese white in particular since it is the finest ground white pigment available in the US market. I did not have roaring success getting a good exposure, it took a long time and the margins were not clear on the image. Now, let me emphasize that this was way back a few years ago when I first started printing gum. And today, I might have way better luck with things, as I know a lot more about how to make difficult pigments work.

As for glass as a substraight. I know that there are people who do that...somewhere. My problem was always in getting the emulsion to firmly and evenly adhere to the glass. Plus I'm confess to being more than a little clumsy...and probably playing with glass sheeting should not even cross my mind, so after a few nice slices around the edges of my extremities...I gave it up for Lent and haven't gone back to play in that playpen since.

Check out http://www.alternativephotography.com/
There is lots of info there.


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