U of S | Mailing List Archive | alt-photo-process-l | Re: gum exposures with NuArc 26-1K?

Re: gum exposures with NuArc 26-1K?

OK Erie, you asked for it... I'm in a foul mood tonight, which is not your fault, but both places where I'd counted on getting a sugar hit -- from either of two neighborhood purveyors of surprisingly good cookies (one of them a block east, the other a block south) were closed... some kind of holiday, I understand.) That's not your fault either of course, but here's what IS your fault.

Firstly, you wrote this message with a bunch of details, facts, numbers and qualifications in almost one paragraph. I count 28 single-spaced lines without a break. Even if I had my sugar cookie, that would be really hard to follow with full comprehension. Especially if, say, one is reading on a laptop, or a cell phone.

So, admittedly I'm not giving your info my best full-bore high-quality attention... but as far as I can tell, you've changed the subject.. That is, you told us in your first e-mail that you were having such an awful problem you thought you might be crazy. The implication, since you asked how long exposures should be, was that yours were either bizarrely short or maddeningly long. Now I haven't done the math on today's info, but I didn't find any reference to the presenting problem, whatever it was.

Secondly, or thirdly, you seem to be free associating about today's findings.... which is good, tho in a sense re-inventing the wheel, as in, you find you won't get a full density print with one coat unless you try
a different strategy. This is generally the case. Though of course reams have been written, on this list and elsewhere, about one-coat gum... So, have you read the archive? Do you have a book or books on the topic? What is your goal? Do you think the contrast index of 1.8 is a lot or a little? What contrast index would you expect a one-coat gum to require?

Etc. Etc.

Those of course are latterday digressions. Your original presentation IMPLIED a question about exposure times. Is that over? If your intent is only to report "progress so far" in hopes that we'll keep it all in mind and knit the loose ends together tomorrow or day after with advice and strategies (forget cookies), well, this might even happen, but in that case, ixnay on the 28-line single-spaced paragraphs.

But you presumably do have some questions.


On Sat, 26 May 2007, Erie Patsellis wrote:

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.


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...


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