Re: Gum problem(s)

Dichromated colloid processes, including carbon and gum, have a
maximum peak in the near UV at about 360 nm to 370 nm, varying
slightly with pH and type of dichromate. From the peak at 360-370 nm,
sensitivity falls off sharply to about 320 nm, at which point it
starts to rise to another, and much large, peak at around 200 nm,
where it has its maximum sensitivity. The peak at 200 nnm is really
huge compared to the one at 360-70 nm, like Mt. Everest to the
highest peaks in the Appalachians. On the other side sensitivity
falls off very gradually in the violet and blue to near zero at
around 520 nm.

 From a practical consideration the huge peak at around 200 nm is of
no use because UV light in this range is very dangerous to human
being and you should not even consider using it.

BL and BLB tubes are every efficient in exposing processes such as
carbon and gum because they have peak radiation almost exactly where
colloids shown maximum sensitivity in the near UV, i.e. at around 360
nm - 370 nm.

Sandy

>On Nov 18, 2005, at 9:53 PM, Yves Gauvreau wrote:
>
>>Katharine,
>>
>>I have found a spectral output curve for the photoflood and other
>>incandesant lamp and the curve shows about a 12-13% relative output at 400nm
>>and it goes down to 0%, in a near linear fashion, at about 250nm. Someone
>>told me that the gum dichro as a peek response at around 370 nm. (I don't
>>recall the exact number) This would mean an output of just above 40 Watts at
>>that peek.
>
>
Received on Sat Nov 19 08:35:37 2005