From: Sandy King (sanking@clemson.edu)
Date: 11/29/02-12:29:19 PM Z
I think Dave is right in that the tubes sold at Home Depot are BLB and not BL.
BLB tubes may be slightly less effective than BLs but the difference
in my experience is so small as to be virtually insignificant. I am
now using as one of my UV light sources, together with a 1000 watt
HID mercury vapor lamp, a bank of (14) 48" BLB tubes. According to my
tests with BL and BLB tubes exposure times for both carbon and
kallitype printing would be about 1/4 stop faster if I replaced the
BLB tubes with BLs of the same sizes and wattage. However, for me the
convenience of being able to pick up tubes of this size off the shelf
at the Home Depot is considerable.
For the record, BLB and BL tubes of the same make and wattage put out
almost identical amounts of UV radiation. The difference between the
two is that the BLB tubes filter out about 95% of the light between
410-435 nanometers, and all of it over 435 nanometers. BL tubes, on
the other hand, have a fairly large radiation spike in the visible
light range at about 435 nanometers, with smaller spikes at 545 and
575 nanometers. The spectral distribution chart for the two tubes is
for all practical purposes identical between 300-400 nanometers.
Sandy King
>Mateo,
>
>The only thing is please take out a tube and read the label on the
>tube. I found that most of the time the "BL" tubes sold in these
>stores (and the packaging usually says Black Light tubes for
>parties, discos, etc.) are actually BLB (Blacklight Blue) tubes. The
>actual printing on the tubes will tell.
>
>BLB tubes are usable for alternative processes but are less
>effective (that is, same wattage but less UV radiation in the range
>that we need) according to experienced users on the list.
>
>Dave S
>
>>On my weekly run to Home Depot this week, there were at least 12+ BL tubes
>>on the shelf in the foothills of Denver.
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