RE: BL vs BLB tubes for cyanotype

Eric,

I am puzzled by some statement you have made about Starphire. In your
messages of today you have suggested that Starphire glass transmits a
significant percentage of radiation below 350 nm. And you have been
saying this for a very long time. For example, in a message to the
alt-photo-list back in December of 1999 you wrote, and I cite the
message:

On Sat, 4 Dec 1999, Eric Neilsen wrote:

OK , I found my charts. Starphire transmits 35.5 % of UV light @
300nm where Standard transmits .3%; @310nm 53.1% Star and .8%
Standard; @320nm 67.9% Star and 9.1% Standard,; @330nm 79.2% Star and
34.4% Standard; @340 86.1% Star and 61% Standard; @350nm 89.1% and
77% . At 360nm and above it stays at about 91% for Starphire and 86%
for
Standard.

Contrast your information with the specifications in this link,,
http://www.pgo.com/pdf/ppg_starphire.pdf, which gives the following
figures. Unless I am missing something terribly obvious, your figures
are very different from those at this source, which are:

Starphire Glass

Transmisson: (@ 5.6mm thick)

@330 nm < 5%

@350 50%

@380-680 nm 90%+

I am wondering if somewhere in your research you did not confuse
Starphire glass with Sapphire glass? In fact, the figures you cited
in the 1999 message for Starphire are much closer to current
transmission figures I was able to get today on the web for Sapphire
glass.

Sandy
Received on Wed Nov 16 18:22:17 2005