uv light source for alt process

[Trevor Crone]

That's great help Trevor, thanks a lot again. I'm getting into pt/pd myself but will also be using it for cyanotypes too. How did you rig the lights up to an enlarger timer? that's a very sweet idea. My cousin is making me a 12x16 contact printing frame so an exposure unit the same size as yours would be ideal. likewise, I'd like the opportunity of printing larger than 10x8 if I wanted to. Initially I was just going to use 2 lamps with uv bulbs either side of the print, would that idea have fallen flat on its face? Could you give me the exact dimentions of the cabinet please. I'll go order the bulbs today.

Gareth, the interior dimensions are; 17" high x 16.1/4" wide (this would be too small if you are using a contact frame for 12x16" prints) x 15" deep. This little cupboard is an ideal size for me as it sits on the floor under the enlarger bench.

All nine lamps are wired in parallel, 3 rows of three, to provide me with not only light intensity but evenness of illumination (very important). The lights are wired to a terminal block and from there a single 3 core cable is then connected to a Viponel electronic timer which has an exposure range of 0.1 second to 16 minutes, anything longer I just hit repeat. If you are going to use an enlarger timer make sure it is powerful enough to take a total of at least 300W (my lamps are a total of 225W). The lights are fitted to a removable shelf that I can slide out for maintenance if need be.

I've also fitted an electric fan (separate circuit) to help cool things down during long exposure times. Although the cabinet is well ventilated; slight gap below door and two adjustable louvers at the top to allow free circulation of air.

When I have to dodge and burn I wear sunglasses, just to be safe, as the door is open and the UV light is quite bright. This is another reason I wanted the light box on the floor so its away from eye level. Although BLB UV lamps are safe if you use sensible precautions.

Hope all goes well and do let me know how you get on.

Trevor.

[Jarvman]

How do the strip lights compare to the bulbs? I'm thinking it might be easier to have 5 of the 18" wide ones attached to the underside of a 22" piece of board with 3 wooden sides keeping it upright. A panel at the back, two at the edges and nothing on the front or underneath. That'll sit ontop of a work surface when I'm using it then and can get taken in and out of the darkroom.

[Trevor Crone]

I attended a super workshop on Pt/Pd printing which was run by photographer Ian Leake and Ian has a UV box which uses 8 - tubes at a distance of about 6" from the printing frame and they work really well. I went for BC fitting UV lamps because it is easier for me to switch from them to an ordinary tungstan lamp for contact printing with the new silver chloride paper, Lodima. Even 1 - 25W UV lamp was way too fast for this paper.

[Tom Kershaw]

Trever,

What variety of lamp are you using for contact printing Lodima?

Tom.

[Jarvman]

Ahh I gotcha. That's worth knowing seeing as I'd quite like to try that stuff some day. Cheers.

EDIT: Actually, I've just found these for a really good price locally. Think these would do the trick?

http://cgi.ebay.co.uk/ws/eBayISAPI.d...:X:AAQ:GB:1123

[Trevor Crone]

Trever,

What variety of lamp are you using for contact printing Lodima?

Tom.

Tom, 1 x 75W Philips Photocrescenta, 8" from paper gives on average 12 second exposure time, and the eveness of illumination is spot on. But I would have thought any decent opal lamp would do, and they are cheap.

[Trevor Crone]

Ahh I gotcha. That's worth knowing seeing as I'd quite like to try that stuff some day. Cheers.

EDIT: Actually, I've just found these for a really good price locally. Think these would do the trick?

http://cgi.ebay.co.uk/ws/eBayISAPI.d...:X:AAQ:GB:1123

Gareth, yes, these will do the trick.

[Jarvman]

Well here it is then! Thanks for all the help Trevor. There's some paper drying in the darkroom coated in cyanotype solution as I type this