I am not sure how much information there is on the web about
flash lamps. The data on large lamps below is from an early
edition of "The Photo Lab Index". I think this one is c.mid 1940s.
Flash lamps were made in at least three classes based on the
delay of the lamp reaching full intensity when set off:
Class M or medium, 20 milliseconds, covers most small and medium
sized lamps with shredded or crumpled foil in them. Class S, or
slow lamps, about 50 milliseconds, meant to be used open flash.
These are very large lamps also filled with foil. Class F, or
fast lamps, about 5 milliseconds. These are gas filled and are
meant to be used on box cameras without any sort of
synchronizer. They will also work on shutters synched for strobe
provided the shutter speed is fairly long. The flash duration is
short so there is some motion stopping ability. These are all
miniature lamps. There is also a Class FP or Focal Plane lamp.
These have a long, drawn out flash for use with focal plane
shutters within certain limits. On Speed Graphics they will work
on the 4x5 when its set at maximum speed where the travel time of
the shutter is shortest. On 35mm cameras they will usually work
at all speeds. They can of course, be used with standard shutters
but much of the light will be lost if the shutter is not running
slowly. There were also various miniature lamps to fit special
holders but the four above were the ones that were common. Flash
lamps were always rather expensive and a bit of a bother. One had
to carry them around and have some means of disposing of them
although news photographers often just dropped them (crunch).
Also a bag full will set each other off. In fact a trick that
works on some bulbs is to stuff a second bulb in a reflector so
its pressing against the regular one. The second one will go off
with maybe half the normal output. Later bulbs were designed not
to do this as a safety factor. Radio transmitters could also set
bulbs off but, again, the same safety treatment tended to prevent
this. Bulbs make a frying sound when they off. This is from the
safety coating on the lamp, intended to prevent them from
shattering. They also have a very distinctive odor, also from the
lacquer. Batteries need to be fresh or the bulb might not go off
or flash with reduced power. BC flash guns were intended to
prevent this.
Where the camera had a magnetic solenoid tripper and
synchronizer on it the demand might be enough to lower the
voltage available from the batteries to the point where the
shutter might not trip or the lamp not flash or both. Kodak and
Compur shutters and others where the force needed to trip the
shutter was increased for its maximum speed often had this
problem. One advantage of Wollensak shutters is that the triping
force is the same at all speeds so they are more reliable with
magnetic synchronizers.
My recent experience with modern alkaline batteries on
magnetic trippers is that they seem to have more oomph than the
old zinc-carbon type. I can get the shutters (Kodak) to trip
reliably at 1/400 second although I have not tried it with a bulb.
Bulbs do age so really old ones may not be reliable. Higher
tripping voltage probably compensates for this but I don't know
for certain.
The foil is mostly aluminum and magnesium. One company called
it "magnalium". Lamps with crumpled foil are probably old enough
to keep as collector's items.
Wabash, which later became Sylvania, had an indicator that
was blue but turned pink if the lamp was gassy. "Blue Dots Mean
Sure Shots). I don't know what this substance was or what gas was
in the lamps.
BTW, arrays of large flash lamps were often used for
lightening effects in the movies.
It seems my fate to collect knowledge about things that are
obsolete.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
