U of S | Mailing List Archive | alt-photo-process-l | Re: Pinhole gums

Re: Pinhole gums

No, 60 should be fine; most of the time I lived at the beach I was
working at temps in the 50s without ever a problem. But last winter,
I found that 42 (even with a heater going full blast) is too cold for
gum. I'm not sure exactly where the cutoff is, but somewhere below
50, I think.

Sorry, I'm still skeptical about the gelatin being the cause of the
overexposure. The problems introduced by sizing tend to be related
to coating and to staining; there's no logic or mechanism I can think
of that would explain the gelatin suddenly causing a great increase
in speed of the paper, just because it was cold where the sizing was
drying. I mean, I won't rule out anything 100% when it comes to gum,
but that really seems like a stretch to me. However, nothing else
makes sense either. I'll think about this more,

Hi Katharine,

Yes, that sounds like problems associated with overexposure,
doesn't it? Even though I was inside, the space where I'm working
has only one heating vent, and I have that cut off, because my flat
file sits on top of it. That room is open to other areas of the
house where there is a lot of heat, but that space is usually
colder-- and last week was probably around 60 or so degrees-- cold
for inside, but not so cold that it should have presented a
problem, do you think?. I'm thinking it was a problem with the
gelatine. I was able to coat it with no problems, though.

On Nov 29, 2008, at 3:21 PM, Katharine Thayer wrote:

Diana, do you have a way of reading the humidity in your
workspace? It sounds, even with the humidifier going, that your
humidity was lower than customary, as evidenced by the problems
with the gum coating setting up too fast. However, there's a
puzzlement here, because as David said, the lower humidity should
mean longer exposure times, but it sounds from your description
that you were experiencing overexposure rather than underexposure
at your usual times. I hate it when things don't make sense.
Another possible variable: I discovered last winter when working
in an unusually cold space that the gum process doesn't work well
below a certain temperature, I'd say 48-50 F. But if you were
working inside in a room that's reasonably temperature-controlled,
that should be a problem.

As long as the gelatine didn't set up before it soaked into the
paper (agreeing with David again) I don't think sizing was your
problem here; I think it's something about the environment/
humidity, although it's not behaving as I would expect from my
experience and from industry research related to gum and
humidity. So that's a little baffling.


On Nov 29, 2008, at 11:51 AM, Diana Bloomfield wrote:

Hi David,

Thanks. I didn't think the gelatine was cooling, but possibly
that was happening. The humidity had definitely dropped-- very
dry cold weather. I usually use a humidifier before coating the
gum/pigment/dichromate mix, and I used the same exposure times as
always. So what's happening-- when I coat the paper (inside),
doing everything I've been doing-- the coating seems to be drying
really fast, as I brush-- even though I'm using a humidifier. I
use the same exposure times that have been successful for me in
the past. So when I take out the paper, after exposure, I can
see the faint outline of the image-- but after soaking it in
water, forever, nothing ever happens. If I brush away the
pigment, that helps-- but basically the image just sits there
undeveloped for the most part. So should I be increasing my
exposure time because of the cold, or is my problem in the
sizing? When I was using all this great paper I'd sized over the
summer (when it was hot and humid), I had no problems, so I'm
thinking my problems are at the sizing stage. ?

On Nov 29, 2008, at 2:33 PM, davidhatton@totalise.co.uk wrote:

Hi Diana,

You have to be a little careful that the gelatine doesn't cool
of before it soaks into the paper. Also if the humidity drops
due to the cold, exposure times will probably lengthen. What
problems are you having??

David H

On Nov 29 2008, Diana Bloomfield wrote:

Thanks for posting those, Marek. That is brave of you to post the
originals, too. I like the rich red of those. Almost of my gum
prints have been made with either pinhole, zone plate, or a toy
camera. I made my first couple of gum prints from a lens-based
camera only last week. I couldn't believe how much easier it was to
register from a sharp, well-defined negative. I had no idea.

I do have a related question maybe you or someone else can answer I
always size my paper, and dry it, outside, and I sized a batch last
week when it was unusually cold here. I had my gelatin and hardener
in one of those electric pots that keeps warm, but I still had to
coat fairly quickly. I've had a lot of gum-printing trouble with
that paper ever since. So is that a known problem-- coating gum, or
sizing, or hanging it up to dry-- in relatively cold weather? Or
should that not make any difference?

On Nov 29, 2008, at 12:38 PM, Marek Matusz wrote:

> Wow
> It has been so quiet on the list that I decided to post some
> pictures printed over the holidays. They are gum prints made from
> pinhole photographs. I have done the worst thing by posting the
> originals as well, but maybe it will create some discussion
> Marek
> http://picasaweb.google.com/marekmatusz1/
> TricolorGumBichromatePinholePhotographs#
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