Re: UV Box Heat Fogging?

>From my experience there are two types of heat fogging that can happen in
gum printing. One is if the darkest parts of the negative (the most heat
absorbing thing in the way of the light) gets hot. This can create a reverse
image, that is the negative will print a negative. The other is by the glass
heating up as more exposures are made which would cause a general fogging. I
have made fuzzy direct positives by exposing gum to infra-red heat lamps
which will heat the negative very effectively.

Jack

> From: Michael Koch-Schulte <mkochsch@shaw.ca>
> Reply-To: alt-photo-process-l@sask.usask.ca
> Date: Tue, 22 Nov 2005 11:04:38 -0600
> 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 21:17:42 2005