Making a tri color gum print 

Devon Fox Thanks! The bulb I was using here was just a standard "party" black light bulb. I think I picked up a couple from Walmart. I haven't had time to make prints with it lately, but I've found that using a halogen worklight to give faster exposures -- just make sure you remove the glass UV filter first!

Schaut ja total einfacht und klar aus. Kriegt auch tolle Farben hin..... Naja, unsere sind ja auch nicht schlecht geworden Küsschen

Hey Bozhidar! Sorry for the late reply. It covered the entire print area (no vignetting that I never noticed). I don't know how many watts it was rated for, as I don't have the original packaging anymore. I did move on to halogen lamps eventually, but the exposure times weren't reduced all that much vs. the additional power it consumed.

+Susie B Hey Susie, sorry for the long response time. I use a saturated solution of potassium dichromate and water -- saturated means I keep adding more until it won't dissolve anymore. That should be right around 13g per 100mL of water. Then I use equal parts of this solution and the gum arabic solution, and mix them together with the watercolor.

Hey there. You don't need all that much to get started... Gum Arabic (I get mine premixed from Photographer's Formulary) Potassium Dichromate (~50g) Watercolors Watercolor Paper Paintbrush Black Light (or halogen light) Negatives Once you get a hold of the Potassium Dichromate and Gum Arabic, the materials will last you a super long time

How much does gum arabic, porassium, and black lights cost? Where can I get those? Can I get those at Walmart?

You can pick up Potassium Dichromate and photo-grade Gum Arabic from Amazon. I got my blacklight from Walmart years ago, so you can probably get by with that. Just remember, be very careful when handling the potassium dichromate.

Great eye! I used to live over on Murray Hill back when I made this video.

Nice, I lived in Little Italy and worked at the Murray Hill Market when I was in school.

+Alexander Timoshenko Look into something called the "Chiba System". I believe it's a method to emulate a gum print, using ferric ammonium citrate to replace the dichromate. It looks like it's slightly more complicated, but it should be a workable alternative.

Awesome! Thank you! It's time to start shopping.

Hey Hosney! I used graphite in the video. This can work alright, but it often leads to the layer becoming very fragile, and falls off easily in the water. I would recommend instead just using black watercolor paint

Thanks, this video is amizing.

I'm assuming here he's using watercolor paint, that's sort of the the standard when it comes to gum bichromate but certainly isn't the only option; any water soluble pigment will do the job.

Works on anything you can coat and rinse. A friend of mine use to print her desing on cloathes and fabrics like this, it reacts differently tho, depends on what fabric you use, some absorb the sollution deep into itself and were hard to work with while rinsing

Hey Julia! If you haven't tried it by now -- yes, it works fine under sunlight. The exposure should be reduced considerably. I never did it much myself, as there were already too many variables in this process to control for. Good luck!

Hey Sara, I've never really been able to really get all the wrinkles out of this project. I think I was just using a crappy printer with no color curves in photoshop, so most of them didn't really come out too well. But here's a good starting point: Prepare a saturated solution of potassium dichromate and water (~13 grams of KDi in 100mL of water, keep adding until no more will dissolve in the water. Be careful with the KDi!!!) I'm not sure what my gum arabic concentrations are, I use a premixed bottle from the Photographer's Formulary. It'll last forever. My watercolors are cadmium yellow, alizarin crimson and phthalo blue for YMC respectively. Mix about 800mg of your watercolor + 15mL (1 tablespoon) of Gum Arabic + 15mL KDi solution. If you're using a black watercolor, use about 200 - 400mg. If you don't like the final print's color balance, try messing with the color balance in photoshop and reprint the negatives.