Re: BL vs BLB tubes for cyanotype

ryberg wrote:
> Loris and Sandy,
> I was more surprised than you at the 3 minute exposure. My
> first test strip was 8,9,10,11,12,13 minutes--all overexposed. So I
> did another at 3,4,5,6,7,8 thinking that perhaps I was mis-reading
> the 8 minute test. My homemade unit is very simple. It has 6
> type F15T8 bulbs on 90 mm centers and places the bulbs about 95 mm
> above the glass of the contact frame. The glass is standard hardware
> store glass sold for window replacement.
> The ballasts and first set of bulbs were surplus from American
> Science and Surplus, sold as "party lights." I bought 6 of them,
> took them apart and glued the sockets on one side of a piece of
> standard hardware store shelving material (plastic coated pressed
> wood fiber.) I screwed the ballasts on the other side and drilled
> holes for the wires. I prop the unit on two matching cardboard
> boxes. As simple as I could make it. I assume the original bulbs
> were slower than the normal BLB bulbs and
> that is why I got such a dramatic difference.
> It sure is nice to have a 3 minute turn around instead of a 15
> minute one.
> Charles Portland OR

I'm guessing the speed is because of the glass you are using. I use a
Patterson contact printing easel and compared to shooting an emulsion
without glass it slows everything down a least a stop or more. I've never
measured it but occasionally when a bit of emulsion hangs outside the frame
it typically is twice as dark as what's inside the frame. Hardware store
glass, I'm trying to remember how they rate it isn't it a "diamond" system,
two diamond, three diamond?

~m
Received on Tue Nov 15 16:52:39 2005