Re: son of a gum tonal inversion test

Mark asked:
You are using the 6 minute exposure time for doing full color prints with
2 gum & 1 Cyanotype layer, correct? Do you use a different exposure time
for the Cyanotype layer?

I use the same time for all three, but the cyanotype time wasn't arbitrarily
chosen, because with cyanotype, like pt/pd etc., once it's "laid down" it
cannot be removed. So the fact that they are all 6 minutes is a coincidence
with the cyano.

 Mark said:
I would guess that the 6 minute time is not necessarily "arbitrary", but one
that from experience you found gives you a more stable printing with gum.
Since you are doing full color prints with more than one printing, it
probably
allows more leeway than if you were trying to do a single coat print. And
you
have more leeway in "Hosing Away" the excess density you do not want.
However, a lesser exposure would not give you that luxury, since it would be
lost in the initial soak/development. It's easier to take away than to put
it
back.

This is all correct. Stable, yet not overexposed or underexposed, but within
an acceptable range, even according to my SPT. In other words, my SPT may
not have step 1 and 2 differentiated but everything else is.

One thing i will say that is interesting from all the test wedges I've seen
of late--I seem to be getting a lot more steps (not STOPS--we need to make
sure steps and stops are differentiated, stops being either 2 steps on a 21
or 3 on a 31) than some I've seen--probably proving the adage that potassium
dichromate is slower and more contrasty. Can't wait to get my website going
this cmas and then be able to post my wedges--mine is bigger than yours kind
of thing....

Mark said:
Also, you are not talking about a huge difference in exposure time under
those circumstances, given multi-coats and the advantages of mechanical
development. I assume that your highlights are clearing as they should, so
your
exposure time cannot be that far off, though the calibration step of the
negative's density can compensate for that end of the scale.

Correct--if 4 minutes or so was my true SPT, then 6 would only be 1/2 stop
greater exposure, not a biggie...I did initially correctly calibrate
according to the SPT, and ended up having very fragile layers that would
tend to bleed a bit into the borders of the print when i would hang them to
dry. Since I love to slap around my gum prints (not my men) this wasn't
working for me, but a more delicate gum printer might find those shorter
times acceptable. Certainly back in the day it was--they would expose so
that the layer was soft and bleedy and produced more watercolory looks.

Now if I could possibly finish writing my view camera final exam I might
even be able to gum print...
Chris
Received on Wed Dec 7 08:59:29 2005