Question about NuArc 26-1K

This week I have been printing some multiples of a negative in
palladium, exposing with a NuArc 26-1K. I have experienced a lot of
difficulty in printing exact duplicates, even though the integrator
appears to be working as it should. The situation is that I am
printing one after the other, with just enough time between each
printing to change the negative from one piece of sensitized paper to
the next. What I am finding is that each printing results in slightly
greater density on the print than the last, with the last of four
about 1/4 stop more dense than the first of four. I develop all four
prints at the same time so processing is not an issue.

I thought for a while that the problem was a coating one, but nothing
I did to get greater consistency in coating helped. Then I decided to
try to print the negatives with my BLB exposure unit, which is also
controlled by a light integrator. Result. Four prints of identical
density. And just to be sure I did it again with the BLB unit with
the same result.

So I appear to have a problem with the NuArc, but why? If I only
print once and then not again for 15-20 minutes I get perfectly
consistent exposures with the NuArc. What appears to be the case is
that as the bulb heats up the response of the integrator is changed.
But why?

Would like to hear from other NuArc 26-1k users to know if you have
been able to make exact duplicates printing the way I described above.

Sandy
Received on Wed Aug 17 13:24:56 2005