My conclusion is that the problem is not related to mechanics of the
enlarger. I believe the problem is a phenomenon called "Negative
Popping". This concerns the heat of the lamp on the film backing.
Bessler has two solutions, both about $25 locally: (1) Heat absorbing
glass, which has been around a while and (2) a new product they call a
Temp-guard filter.
Has anyone else had this problem and/or solved it with one of the two
fixes above? Also any other thoughts/ideas?
Thanks and cc's to my email address appreciated.
Rick Schiller
RSc...@aol.com
You should be able to confirm the negative popping with a grain
magnifier. Let a negative get good and warm and then focus it
sharply. Let the machine cool for a few minutes and then turn it on
again while watching through the magnifier. If its popping you will
see an out-of-focus image that will drift back into focus after it
gets warm. A glass type negative holder is the ultimate cure for this
(at the price of four more surfaces to keep squeaky clean). I
sometimes have to resort to using the red filter as a lens cap so that
I can leave the light on between focussing and inserting the paper. I
then turn the lamp off for just long enough to swing it away and start
the timer.
Heat absorbing glass will certainly help. If you are doing color
work you should have the heat absorbing glass anyway.
---
Richard Knoppow
Los Angeles, Ca.
dick...@ix.netcom.com
You might also want to consider investing in a cold light head for the
enlarger. Not only will this stop your negatives from popping, you will
also produce much more beatiful prints.
Good luck!
They also sell an item 8132, which is a heat filter. I don't know what
this is, but when I called Calumet, both items are the same price
($27.39), so I suspect they're pretty similar.
I have no experience (yet) with either item, but I plan to, soon....
Lou
Luca (lu...@cs.stanford.edu)