[APML] 40C thermostat for hypering

[Philip Perkins <philip@astrocruise.com>]

A few people asked me off-list for details of the 40C thermostat for 
hypering with the Lumicon equipment.  Lumicon themselves offer 50C or 30C 
probes but do not offer a 40C probe.  50C is most widely used, especially 
by 35mm users.  Results speak for themselves and the process is effectively 
"proven in use".  However it is a very high temperature and nearly double 
the recommended top limit for any kind of film handling.  I'm not aware 
that anyone has conducted side-by-side experiments using 50C and 
30C.  Without this the possibility exists of some slight detrimental effect 
from using 50C.

To avoid such uncertainty I thought about reducing the 
temperature.  Reduced temperatures also give better repeatability - part of 
the problem with 50C is that chemical reactions happen quickly - too 
quickly in some cases.  Another side effect of high temperatures can be 
uneveness.  A possible solution might be to use 30C, except that this 
results in overly long hyper times - more than 2 days instead of 7 hours at 
50C.  Even so I use 30C for all my 120 format work because higher 
temperatures result in uneveness (with the film rolled up).  For other work 
40C would seem to be an ideal compromise.

I traced the original manufacturers of the Lumicon probes:

PSG Limited L.L.C.
1225 Tunnel Road
Perkasie, PA 18944
USA

tel: 215-257-3621
tel: 800-782-8412
fax: 215-257-4288

I think the part number for the probe is TRS 715.  They do not seem to have 
a web site.  Try speaking to Donna if she is still there (this was more 
than two years ago).  They supply to the industry and were not particularly 
keen to supply a one-off to some private individual.  I succeeded after a 
bit of persuasion - I seem to remember Donna saying she was "charmed by my 
accent" so if you encounter reluctance you may try speaking in some wierdo 
voice :-)  If there are several interested in the 40C probe then I suggest 
soliciting Lumicon to order a small batch from PSG - because of the volume 
purchase the price will be quite a bit cheaper.  I forget exactly what I 
paid for mine, but it was significantly more than the Lumicon price.

Cautionary note:  When the probe arrived it looked fine and was clearly 
exactly the same kind of thing as Lumicon supply.  However it cycled at 
46C, not 40C.  I contacted PSG.  They were not very compromising and said 
it was impossible for this to happen because of the tests they run.  I 
persisted.  They said that if I wanted to return it, they would test it and 
return to me when they found that there was no problem.  I said that I was 
in a hurry (lunar cycle problem).  The only way round it was to order 
another 40C probe and pay for it.  When the new probe arrived it cycled 
perfectly at 40C.  I returned the original probe and asked for a 
refund.  After a while when I had heard nothing I contacted them and they 
said that they had tested the returned probe and found that it was the 
incorrect part.  The refund appeared about a week later.  The correct 40C 
probe has been working fine.

--Philip
Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com


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