Re: gum exposures with NuArc 26-1K?

[Erie Patsellis <erie@shelbyvilledesign.com>]

Progress so far:

due to ease of availability (pretty much what I had on hand) I'm using 
the following:

Varn 100% Gum Arabic Solution. I did some digging, some people like it 
for Gum work, others hate it, this can is a very, very light amber and 
so far, (4 prints) I've had no staining.

Potassium Bichromate

W&N and Grumbacher Watercolours

I mixed a saturated solution of Pot. Di., added a bit of Lamp Black (I 
know, but the only Payne's Grey I have is an off brand and I wanted to 
at least not chase my tail, yet) to some Gum, stirred until in solution, 
added gum and Pot. Di. 1:1, coated some watercolour paper I had lying 
about. (probably Lanaquerelle 140# HP). let it dry and contact printed a 
4x5 film neg with a CI of about 1.8. for 90 units on the NuArc 
Integrator (calibrated so when bulb is up to full output, 1 unit is 1 
sec) First results are promising. Hadn't thought about paper or OHP negs 
(yet...) I'm just trying to reduce variables until I get as much of a 
hand on the process as I can. I can definately see digging up some 
contrasty 8x10 negs today and trying a few sheets though I'm still 
working out a consistent, easy to implement registration system that 
doesn't screw with the negs. Once I get this down, I'll probably do some 
enlarged negs of some 4x5 work I've wanted to print larger, I have a 
full 42" roll of N31P stashed as well as a bunch of sheets of N31P and 
various lith films that I've been able to get a handle on the CI after a 
few tests shots and have a somewhat workable methodology to get the 
desired CI, though most of the film I've been shooting has been destined 
for scanning and I've been processing for a CI of about 1.6 or so, so I 
can keep the film curve on the linear area of my scanners response 
curves. It would be trivial to get a CI of 2.5 or so, as my early 
attempts got me into that area accidentally. I can definately see that I 
will have to do multiple coatings to hold highlights and shadow, as so 
far (4 prints, all done last night, remember I'm a gum virgin) it seems 
to be an either or with my "standard" negatives. Any and all advice, 
criticisms, (beer, wine, coffee) will be greatly appreciated, as I'm 
trying to get a handle on gum and cyano before I start school (Finally 
decided after taking a year off in '81, and that the year surely must be 
up by now, that I really should get my BFA if I'm to get anywhere doing 
what I enjoy) and the more difficult of the two seemed like a sensible 
starting place to me.

erie



Judy Seigel wrote:
> On Sat, 26 May 2007, Erie Patsellis wrote:
>
> > Just as a sanity check, is anybody on the list exposing gum with a 
> > NuArc platemaker? what are your exposures running?
> Do you think yours are too short or too long?  Mine were always very 
> close to exposures with the BL fluorescents as for a long time I used 
> them interchangeably -- from 1 to 3 minutes.  If yours seem long, is 
> your glass clean?  Have you cross-checked in sun... maybe your am di 
> is too weak, or contaminated?  Or negatives too dense? Gum needs 
> density range of about 1 (IIRC, it's been a while since I measured.) 
> Or are you mixing emulsion too far in advance? Or letting coated paper 
> wait too long?
>
> I also note that when I changed from film neg to paper neg (inkjet) 
> exposure times were about half... or less. Paper doesn't have the 
> built-in filters.
>
> Good luck...
>
> J.
>
>
> >
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