Re: UV Box Heat Fogging?

What I was trying to do was to see what the limits of a colorized negative
are in regards to blocking UV. I'm normally printing to VDB around 1.8-1.95
which takes about six minutes. For my own curiousity I doubled that time,
and then doubled that again (6, 12, 24 minutes). At 24 minutes things
weren't looking like what I thought they would. I wondered if heat energy
was becoming a factor on the emulsion exposure overall. Hence the question,
does heat fog exist in these situations?

~m

Loris Medici wrote:
> Well, if you can get maximum black with a specific exposure time and
> also have a color that gives you paper white with that exposure time
> what's the point in exposing for a longer time? I guess even a
> stouffer 31 step table can show print density at step 31 (log 3.0)
> with enough exposure - it isn't 100% opaque to light.
>
> -----Original Message-----
> From: Michael Koch-Schulte [mailto:mkochsch@shaw.ca]
> Sent: 22 Kasım 2005 Salı 19:05
> To: alt-photo-process-l@sask.usask.ca
> Subject: UV Box Heat Fogging?
>
> Does anyone (else) experience what I think is heat fogging during UV
> exposure. I'm using an eepjon like box with GE BL tubes 15/20s. I was
> doing some max density tests on a new step wedge and started to
> double and triple my exposure to see how effective my negative was at
> blocking UV when I started to notice two things. The first was edge
> bleed on squares which should have printed clean. The second was a
> general fogging toward my densest squares, or so I think. It could
> also be the color ranges I've selected are not providing enough
> contrast and therefore I'm just not able to clearly define white. The
> thought occurred to me that once the emulsion starts sitting in the
> oven for 24 minutes instead of say six perhaps heat becomes an issue.
> Thx.
>
> ~m
Received on Tue Nov 22 13:30:50 2005