Warming up a coldlite

electric dust wrote:
 > Do any of you using a coldlite see the need to warm it up for a
period
 > before using it? The older version (not for VC ) I've used for a long
 > time and have never seen fluctuations, and have never needed a
voltage
 > stabilizer to guarantee repeated times. My year old VC model,
yesterday
 > went all over the board for a frustrating 30 minutes before
repeatable
 > times were established. Sunspots? If the problem is elsewhere, I
still
 > can't find it. Apertures were correct. That leaves voltage
 > fluctuations, unlikely, or multiple personality Agfa paper. Also
 > unlikely.

Gaseous discharge lamps like cold lights like to run hot. The
output will increase as the lamp warms up. Aristo puts a heater in its
lamps so that it can be used intermittantly but even these lamps should
ideally be run continuously and exposure controlled with a shutter.
Older cold light lamps without heaters will vary even more if operated
intermittantly. Also, as fluorescent lamps age they become more
temperature dependant. For consistent exposures you really need some
sort of simple shutter so you can leave the lamp running throughout the
printing session.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk.TakeThisOut@ix.netcom.com<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Warming up a coldlite 

"Richard Knoppow" <dickburk.TakeThisOut@ix.netcom.com>
 >
 > Gaseous discharge lamps like cold lights ... consistent
 > exposures you really need some sort of simple shutter
 > so you can leave the lamp running throughout the printing session.

You really need both a shutter _and_ a compensating timer,
and a regulated power supply (80-140 in, constant xxxv out).

You can get away with fluorescent/cold lights and a
timer [of the f-stop variety, naturally] if exposure
is not critical and all exposures are substantially
of the same magnitude.

A heater helps but you have to turn the heater off when
the lamp is on, and the heater must draw the same power
from the wall as the lamp. With most 10 second exposures
I doubt if this level of sophistication is noticeable
but you may want to plug your heater into the safelight
output of the enlarger timer for that certain je ne c'est
pas. [Cretin (sorry, can't help it) will write an
article within the year declaring this hook-up as vital.]

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Warming up a coldlite 

electric dust wrote:
 >
 > Do any of you using a coldlite see the need to warm it up for
 > a period before using it? The older version (not for VC ) I've
 > used for a long time and have never seen fluctuations, and have
 > never needed a voltage stabilizer to guarantee repeated times.
 >

"The older version ... "
The surplus 4 x 5 F. Tube enlarger I purchased in 1958 did not
use a shutter and took zero time for warm-up. Worked off my Time
O Lite; just push the button. A very solid enlarger it was, with
four or five small diameter tubes.
To read the posts this thread I think it likely some have not
yet made it into the mid last century. Dan<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Warming up a coldlite