Starting out Gum Bichromate Printing

Exactly. You make color "separations", different negatives shot through different filters. Or do the separations in PhotoShop (from a scanned color negative or slide, or a digtal camera).

And getting "snappy" colors is sort of like dying easter eggs, print the colors with the most blocking power first, then move towards the most transparent. Probably magenta, then cyan, then yellow.

Thank you for your response. I read one technique is so use opaque material to "dodge" out that color.

If you are interested in "tri-color" gum, or CMYK-types prints, I would _strongly_ recommend the photoshop and digital negatives route. I couldn't imagine working in a traditional way, but you could accomplish that through filters and B&W film, or generating seperations from a slide, with much time, frustration and money spent.

Anyhow, the actual process is pretty straightforward. The 3 RGB channels correspond to the three pigments you use: (r) cyan, (g) magenta and (b) yellow. Each channel has its own negative, with different information (look at the separate channels in any PS RGB/CMYK file to get a visual). This is the exact same concept behind CMYK press printing in all its forms, except in Gum, Tri-color (CMY) is more common than CMYK; more from historical practice than anything else. You are definitely going to get a punchier print if you print with black, and there are any number of ways to generate that K channel in PS, but alot of gummists find it unnecessary.

Where your confusion comes from is that in gum printing, it's not always tri-color, it is actually more often monochrome, and selective colorations in specific areas of the composition, sort of like spot colors in magazines and other printed material. Printing gum this way, it is perfectly acceptable to use 1 negative, and you build up density and tone with successive exposures of the same negative with diffent formulations of the gum emulsion. It is a highly nuanced, paced way of working, but is the way many gummists prefer.

Adam, do yourself a favor and pick up this book:

The Book of Alternative Photographic Processes by Christopher James Publisher: Thomson Delmar Learning; 1 edition (June 21, 2001) ISBN: 0766820777

(link)

I don't know what your experience with photography is, but I hope you realize that there is practically 150 years of tradition & technique behind this thing and so many wonderful ways to create your images, and in this digital world, so much of that is being tossed away and people need to rediscover the handcrafted print!

Adam,

I've just started printing tri-color gum and the guide on unblinking eye is accurate, I assume you are refering to the one written by Sam Wang

Start with a color image, invert and apply a correction curve, then split the channels (by the way your image befroe doing all of this because after you split the channels the original image is gone.) Then print each seperation on transparency film such as Pictorico. The hardest part, is building the curve. Use the technique Sam did.

There are more details, e-mail me off list and I can give you more information. The photo I've posted is a snapshot I made on a Canon A75 camera. This was my first successful gum print even though there are some issues with it.

Good luck,

Don Bryant