Thursday, December 13, 2007

More Gum Bichromate Test Prints

I’m still testing three-color gum bichromate prints, trying to work out all the variables. Here’s test print #6:

I added a black layer to this one, as I was feeling that the other test prints didn’t have enough dark values. Rather than start from scratch with CMYK separations, I opened my original test file in Photoshop, split it into CMYK separations, but only printed the black separation. As you can see (or not), the black barely shows up. So, I made a new test file and used it to adjust exposure and gum to paint ratio for the black print.

Here’s the first black test:

As you can see, not too great. I mixed the gum arabic and paint at a different ratio, decreased exposure a little, and ran a second print.

It’s not perfect, and by itself wouldn’t make a good print, but I thought it would work to add some darker values to a three-color gum print.
So, on to test #7:

This one is the best one yet. I’m pretty happy with it, actually. I’m still having some difficulties with registration,. but there’s a couple of things I’m going to try. I think I’ve done all the tests I need, and will start printing my first real gum bichromate tomorrow. There’s a couple of small adjustments to be made, but not enough to warrant another test print. I’m just going to try a real image and see what happens.
I’ll post this image when it’s finished in a few days. I’ve also got several other pieces to post, which I’ll get to soon.

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