Quote Originally Posted by cloudhands View Post
Hey, thanks for the replies, fellas! I'm afraid this might still be out of my range of darkroom technique at this point, but please humor me as I have more dumb questions:
- If I start with a slide, enlarge it onto tmax and then contact print to an ortho film, I will end up with a positive, right? Yes

I thought contact printing in alternative processes used a negative. Yes
- the UV hardens the chrome, and then in washing the hardened areas (along with pigment) does not wash away. So dark pigment for shadows needs mostly clear negative to allow the UV at the coating.

- How can I figure out exposure times? My enlarger doesn't have 1/250sec or whatever increments. It starts at 5 seconds, then goes up by 1 second increments. Stop down to f/16 or so and add neutral density - for example a polariser from your camera kit is good for 2 stops

36cm2 thanks, I did find that article, and was hoping for a bit more detail. This is the part I am interested in:
"By starting with a positive transparency from the camera an enlarged internegative can be obtained in one step on sheet film. If the original small-format image is a colour transparency, projection onto orthochromatic materials (which are insensitive to red light) will not faithfully reproduce the tonal balance. To maintain this, a panchromatic sheet film will be necessary, possibly with a colour head or a filter to bring the enlarger light source to a daylight colour balance."

Tmax is a panchromatic sheet film, yeah? Yep
I have a color head. What does it mean to "bring the enlarger light source to a daylight colour balance?" Light source is tungsten. Most of us print subtractively. I suspect you will need to print longer blue to counter the relative yellow output of the tungsten bulb.

I assumed (naively, apparently) that the process would be something like:
-set up enlarger for 8x10 projection size
-switch off two colors (I have an additive enlarger, so red-blue-green)
-expose a sheet of film, put that sheet in a dark box, marking it somehow to indicate the color exposed
-repeat for the other two colors
-develop the 3 sheets
-contact print using the gum bichromate process

You could do this if you are trying to make separation negatives, with a goal of some sort of very abstract posterization. Or you could be aiming for full colour gum prints I guess, if you are coating multiple gum passes.
good luck -mike