Re: brush vs tray size for gum
About the humidity:
I live in a very humid climate and have no problems printing gum in
high humidity, but a few weeks ago I found that when the humidity
plunged to an almost unheard of 17%, exposing even at 3X my normal
exposure time wasn't nearly enough exposure; the gum just ran off the
paper in development. According to a graph I found in some
information from a printing industry group, that much of a drop in
humidity should necessitate 8x the exposure to harden dichromated gum
arabic to the same degree. But before I tried increasing the
exposure by that much, the wind changed and the humidity went back to
93%, and suddenly everything went back to normal.
So my first thought was that your development was slow and difficult
because with the high humidity, you were using exposure times that
were too long for the conditions, and consequently overexposed the gum.
But this explanation stops making sense (there's those pesky data,
interfering with perfectly good theories again) when it comes to your
observation that unsized paper printed fine and developed well in a
But your observation that with the unsized paper the development time
is closer to the normal development, implying that it's still greater
than normal, indicates to me even with the unsized paper you're
getting some effect of the humidity on speed of the gum, so I think
that may still be probably somewhat of a factor.
But I also wonder whether due to the increased humidity, the sizing
might not have been completely dry before printing; obviously if
unsized paper works better than sized paper, there's probably
something about the sizing that's contributing to the problem, as you
About whether sizing needs to be "aged" before printing:
I've never found this to be true, as I'm always sizing paper on the
fly and printing as soon as the sizing is dry, and I keep wondering
if it's just another one of those myths that keep popping up or if
there's something to it. But one thing I have seen, is that if the
sizing isn't completely dry when printed (and in my humid climate
even brush-sized paper does have to be dried for several hours, if
not overnight) then I've sometimes seen bright yellow dichromate
stains in the paper, and also pigment staining. So while my own
experience doesn't support the idea that sizing has to be aged per
se, it does suggest that it's important to be sure that the sizing is
dry before printing.
As to brush vs tub, I think it's probably a matter of personal
preference. I prefer brush-sizing because there's less glyoxal-laced
gelatin to dispose of afterward, and I find that as long as I keep
the paper warm and the gelatin warm, it brushes out easily enough to
get a good even coat.
On Sep 26, 2006, at 8:49 AM, email@example.com wrote:
I agree that tray sizing is a lot of mess and hassle for no
benefit. Plus, why do the sizing in 2 steps when it can be done in
use either a glass rod (puddle pusher) and/or a brush. I add the
(formaldehyde in my case) to the sizing just before sizing each print.
Three drops of formaldehyde and 5 ml of 3% sizing easily does an
11x14 print. In these tiny amounts, exposure to formaldehyde (or
hardener one uses) is minimal. I get very even sizing this way. A
bit of curl to the paper, but nothing that causes any problems.
I tried B.M. glut and did not like the results. It resulted in slower
development and considerably more staining than with formaldehyde.
As for sizing with unhardened gelatin, that sounds like another in
line of T King's erroneous hyperboles.
Speaking of gum, I taught a gumover workshop in Philladelphia this
weekend for www.projectbasho.org. On sunday it was 80 degrees F and
humidity in the darkroom. That's the first time I've printed gum in
sauna-like conditions and it created some hassles with very slow
development and the need to intervene with some brute force measures
(brushes, fingernails, sandpaper). Anybody have similar problems
gum in high humidity? The conditions seemed to cause problems with
sizing in particular because development was much closer to normal
did a single coat of gum on unsized paper right out of the plastic
speculating that the humidity either prevented the gelatin from
completely or it allowed the gum solution to soak into the sizing a
rather than sitting on top. Despite the problems, I believe a good
had by all. Although I always want things to go smoothly during the
workshops, it's good for the students to learn how to deal with
when they come up.
From: Christina Z. Anderson firstname.lastname@example.org
Date: Tue, 26 Sep 2006 08:08:22 -0600
Subject: brush vs tray size for gum
This weekend was time for sizing paper, and since I was doing small
(11x14's) I decided to tray size instead of brush size to see if it
added benefits to brush sizing.
I was sizing with gelatin glutaraldehyde as usual. I did use a
piece of it
right away, same day, and had no problem with the sizing not being
and producing "magenta squares" as did Carmen. However, I was
that I bought from a medical supply house (now available at the
Photographer's Formulary) and not Black Magic. The gelatin on my
not slimy in any way so I know it was hardened. I am still not sure
Carmen got that problem, and am wondering about the suitability of
Magic, therefore, with its added sulfite. It sounds like the same
had when I tried Terry King's advice to use unhardened gelatin and got
With tray sizing and cautions with glut, I gelatin sized the paper
and then the next day I soaked the sized paper OUTSIDE in a tray of
glut to a gallon of water. That worked well, but I would only tray
the hardening part could be done outside to minimize fumes produced
surface area of a whole tray of hardener, whatever type--glut, gly,
formaldehyde. (When I brush size I keep the solution capped inside a
and pour out a cup at once.) The gelatin paper went in "slimy"
went out unslimy.
The paper works fine but I learned a couple things: paper tray
gelatin will sink to the bottom, not float as does brush sized paper
Arches) so if I am going to leave the paper soaking for a while it
be face up. I learned that the hard way. Back to floaters and
The paper does curl less than brush sized, but it doesn't seem
added trouble of trays. This is the only benefit I can see. Oh,
evenness of sizing? I don't know this one yet...will have to print
My husband set up an ingenious "clothesline" for me--a rung ladder
side has plenty of hanger-ready rungs.
I learned another thing the hard way: I printed 4 prints on the
shrunk paper with a cyanotype layer, put the paper through the hot
sizing process and didn't THINK that the 140-whatever degree
shrink the paper even more and make registration a B---H but you
did--warped and shrunk. Luckily only 4 prints ruined. DUH. Or, as Clay
The bottom line is that brush sizing is sooo much easier and works
uses way less gelatin--I sized 24 11x14s with a a liter of 3%, and
I can do that many 16x20s with the same. I don't think even with small
I would tray size...
That's all my truly exciting weekend experience!
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