Re: UV Box Heat Fogging?

From: Michael Koch-Schulte ^lt;>
Date: 11/22/05-02:31:35 PM Z
Message-id: <004101c5efa3$bba222c0$b300a8c0@Sweetwood>

That's interesting. My easel is warm but not hot. So perhaps not heat as I
thought. On my Stouffer wedge, during the long exposures, the last two steps
are sometimes darker than the steps the precede them. Could "scattering" of
light be part of my problem? I'm using a T2115. What started all this is
that I've been using some new wedges based on the ternary model proposed a
couple of months ago.
Wedge 1:
The original by Clay Harmond was made with 5 steps. I expanded this one to
27 steps to see a little more deeply into model. Based on the results of
printing this wedge I was able to see a more "dimensional" view of where the
"sweet spot" was for my printer/ink/paper/emulsion combination.
Here's the print out at double the exposure on VDB:
It becomes quite obvious that green has the greatest influence, red almost
as much and blue the least.
Based on the green-red results. I made a second wedge which only used the
red-green colors. Green on the y-axis and red on the x-axis:
The "Red Green" wedge (with apologies to Steve Smith):
This is the one that's giving me the problems. Because it's sooo very
effective at blocking light I have to shoot it under the lights longer. What
I think I'm seeing here BTW is an oval area in the upper left region
blocking the most light, centred around R192,G192 or R176, G176 But it's
hard to tell because light seems to be creeping into the edges. Maybe it's
just the nature of the ink, or scattering. I'm going to try it on some other
emulsions and see if I have the same problems. Thanks.


Loris Medici wrote:
> I don't think fogging in your case is caused by heat. I expose prints
> consecutively and my UV fluorescents don't get so hot (they get warm
> but definitely not hot). I didn't read anything about heat fogging of
> vandyke too. The safest way of testing if vandyke gets fogged with
> heat would be heating the coated paper (with a hairdryer for
> instance) and exposing for standard time. If it gets fogged then we
> can say heat fogs vandyke. But this wouldn't indicate the fogging is
> caused by heat in your specific case. Heat from UV fluorescents is
> not the same as heat from a hairdryer. The result you're getting is
> caused by the fact that the negative density and color you use is not
> 100% opaque and after enough (excessive in your case) exposure, you
> get tone in the print. You can try it with a stouffer step tablet
> too; if you expose enough you will get tone in the 31st step.
> Regards,
> Loris.
> -----Original Message-----
> From: Michael Koch-Schulte []
> Sent: 22 Kasım 2005 Salı 21:30
> To:
> Subject: 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
Received on Tue Nov 22 15:23:05 2005

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