Re: update: screw-in BLB light-box

John,

The reason is because HID mercury vapor and metal halide units put
out a very large percentage of their total radiation in the visible
spectrum, where it is not useful to UV processes. This is why very
low wattage BL, BLB and SA tubes, though relatively low in total
wattage, are much more efficient in using the radiation than HID
bulbs.

In my opinion HID lamps are no more effective than UV fluorescent
tubes in penetrating into thick gelatin layers.

Sandy

>Hi Sandy,
>I had read the experiment on the Blinking Eye comparing the various light
>sources..... I wonder why the printing time is almost the same with a bank
>BL bulbs as with a high output light.?
>
> I have several Olec Mercury Vapor combination units that I had
>planned to use............ The output on each of them is a variable 1000
>watts, 3000 watts, and 5000 watts....... I am trying to get great relief
>in my gelatin images and I bought these lights thinking the high output
>would offer more penetration much faster.................. Any thoughts on
>this?
>
>
>
>
>
>----- Original Message -----
>From: "Sandy King" <sanking@clemson.edu>
>To: <alt-photo-process-l@skyway.usask.ca>
>Sent: Monday, August 01, 2005 2:09 PM
>Subject: Re: update: screw-in BLB light-box
>
>
>> Hi Judy,
>>
>> Thanks for the update. Were the screw-in tubes your unit placed as
>> close together as possible? This be taken into consideration in
>> weighing the pros and cons of the screw-in versus regular tubes.
>>
>> The use of 20 watt screw-in tubes in place of 13 watt ones should
>> reduce your exposure by about 1/2, but if your tubes are already
>> placed together as closely as possible that still would not reduce
>> your exposure times to what you observed with the Edwards unit.
>>
>> Sandy
>>
>>
>>
>>
>>
>> >Hello Sandy King (who first posted a query about the screw-in BLBs
>> >as a possible source of UV for alt processes) and anyone else
>> >interested in knowing how they worked.....
>> >
>> >This past weekend, during an excellent workshop on PT/PD printing
>> >taught by Kerik Kouklis at the Cascades Academy of Photography,
>> >which is located in lovely "old town" Issaquah, Washington, I was
>> >able to compare printing times in my lightbox (6 screw-in 13 watt
>> >BLBs with the print frame 4" from Light source) with one of Edwards
>> >Engineering fluorescent tube boxes. Needless to say, the times were
>> >longer - a tad more than 10x - but the results were the same.
>> >
>> >Stated specifically: A digineg created with Keith Schreiber's
>> >method (looks orange on screen but prints yellow-green) and printed
>> >on Pictorico OHP using an Epson 1280 (dye inks) with 100% PD soln.
>> >on Cranes "Platinotype" (B&S name for this paper) required 1 min 50
>> >sec in the EE box, where as the same required 20 min in my box. All
>> >other factors were more-or-less (read "unscientifically determined
>> >to be" ) equal.
>> >
>> >For the time being, as I perfect coating techniques, etc., I am not
>> >bothered by the excessive time - gives me an opportunity to make
>> >notes which I tend to forget to do when I am working at a faster
>> >pace - but will most likely give the 20 watt bulbs a try before
>> >building a larger tube box.
>> >
>> >Anyone know right off the top of their head if I might expect
>> >exposure vs wattage to be linear in this situation (i.e., will the
>> >increase from 13 watts to 20 watts cut my time by about one-third)?
>> >If not, I will go back to some of the published data /
>> >manufacturer's data to search out the answer to this question. If
>> >it is less than linear, I probably wont bother with the more
>> >expensive screw-in bulbs, but just go right to a tube box sometime
>> >in the future.
>> >
>> >Thanks!
>> >Judy
>> >
>> >--
>> >Judy Rowe Taylor
>> >Mukilteo, WA
>>
>>
>>
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Received on Fri Aug 5 12:10:02 2005