> On Wed, 10 Jun 1998, Wayde Allen wrote:
> > I've been using a 275 W GE sunlamp about 24 inches above the print frame.
> > Exposures have been about 15 minutes. Sensitizer is 13% (saturated ?)
> > potassium dichromate solution.
>
> Wayde, is that one of those big hot sunlamp bulbs?
Yes it is.
> If it is, watch out --
> the heat from the bulb can be a definite variable, that is, somewhat cook
> your print.
Yes, I have been watching that.
> Also, with the sunlamp bulb I began with, even at 30 inches,
> exposure was very uneven. Edge falloff was horrendous.
Hmmm, I haven't seen that, but would guess that it probably depends on the
height of the buld and the size of the print. I tried one 8x10 gum print
the other day with the lamp 24 inches above the frame. Didn't notice any
edge fall off, but will have to check.
> My sunlamp was very slow, BTW -- at 30 inches cyanotype took 30 minutes..
Yes, I have found that to be true. I can't say I particularly like this
light source, and am planning to replace it. However, I think I paid
about $3 for it at a garage sale.
Interesting thing is that I tried making a carbon print this last weekend
using bright sunlight, and got a really nice print at an exposure of 1.5
minutes. Using the same tissue with the sunlamp seems to give a much less
contrasty image, and takes between 30 to 45 minutes to expose. Looks like
I'll need to go to a different light source.
> Now you've got me Wayde -- torn between heartfelt gratitude for the plug
> (it is a plug, isn't it?) and "newsletter." Last time I corrected someone
> on that, he explained it's a newsletter if it doesn't have ads... ;- )
> Whichever,,,,, thanks....
Well ... it was intended to be complimentary. I'm guessing you'd rather
it be called a journal ... ?
- Wayde
(wallen@boulder.nist.gov)