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.
I suspect that somewhere in those figures lies the clue to why my gums
were *worse* with the Starphire -- not that it couldn't work the other way
around, but that my process was formulated for a glass that transmitted
differently -- transmission of more of the lower nanometers skewing the
curve in one direction or another. The particular gum used might also
respond differently at different nms, etc. In fact differences of glass
could also account for other unexplained differences...
However, the variables being infinite (little as I know on the topic I do
know different colors & pigments respond differently to UV, as shown in
their different fading & exposure times), I think I'll pass on trying to
dope it all out, especially as my negs & formulas are keyed to "standard"
glass.... But this suggests another variable to look at when trying to
figure out why X used Y's formula, chemicals, & paint, and STILL got
different results.
thanks for the good info...
Judy
>
> Relative speeds for Platinum and Palladium change as the out put goes from 350 to
> 320 with platinum being slightly faster. However, the big difference is in the
> speed in relationship to Rh. If you print at High Rh, 60 to 70% palladium is much
> faster, and conversely platinum prints faster at low Rh 15% to 25%.
>
> So , can you see why I can not say that "the" curve can be substantially effected
> by the change in glass? It would depend on what coating solution one uses and at
> what Rh range is used. What we can see however, is that more UV rays reach the
> sensitized paper with Starphire than with Standard glass and that the additional
> UV energy will increase the exposure that the paper receives.
>
>
> I don't know the sensitivities curves for the different mediums covered on this
> list, so I can't say that other processes would benefit from a change to
> Starphire. I would guess that some would benefit from the unused UV energy that
> standard glass block out, but it may not be enough or have side effects that are
> not desired, as those you have spoken about. One should research the glass, UV
> light output of their unit, and sensitivities of materials used before buying into
> a system as best, better, the ultimate answer.
>
> And what the heck, I have not seen much information on the B-270 that David shared
> with us. I can see that Starphire allows approximately 70% at 325nm or nearly
> twice as much as B-270 which would lead me to not use it, or perhaps not buy it.
> I might use it if I had a sheet to see what it can do.
>
> Cheers
>
> best guesses from EJ Neilsen
>
> --
> Eric J. Neilsen
> 4101 Commerce Street, Suite #9
> Dallas, TX 75226
> 214-827-8301
> http://home.att.net/~e.neilsen
>
>
>
>
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