U of S | Mailing List Archive | alt-photo-process-l | Re: A few gum things

Re: A few gum things

Thanks, Keith. I have no idea what I did wrong-- followed the steps to the letter with the gum/dichromate sizing, but you are correct-- reducing the use of dichromate is certainly preferable. I was actually trying to get away from gelatin as I just don't like what it does to the surface of the paper. Since then, I tried less gelatin and it looks better and still seems to work fine.

Thanks about the gesso information, too.


On Apr 7, 2008, at 10:11 AM, Keith Gerling wrote:

I've tried it and it works fine, but in my case I am trying to reduce
dichromates, so I choose glut as my primary pollutant in place of
another dichromate step.

Until my recent discovery of Masa, I had use gesso for over eight
years.  Gesso on paper (old prints_. gesso on wood, on tap paper, and
primarily on aluminum.  I find that bottled artist's gesso using
acrylic did not have enough tooth and gum.  Some stuff that came from
Canada (forgot the name - white containers with red lettering) worked
OK, but that the best results were to be had with using the "old
formula" gesso: home made with rabbit skin glue.

On Sun, Apr 6, 2008 at 11:27 PM, Diana Bloomfield
<dhbloomfield@bellsouth.net> wrote:
Oh, I would like to also add that I tried that sizing suggestion in James'
book (and I saw it mentioned somewhere else, too) where you size with gum
and dichromate-- I tried that twice and couldn't get it to work. Has
anybody ever actually tried that, and does it work?

On Apr 6, 2008, at 11:16 PM, Christina Z. Anderson wrote:

Maybe this might help, a quote from Mike Ware. Also, Ryuji has posted a
lot of info in the past on glut, and he was the one who intitially led me to
use it. BTW I had not told Mike what strength I was using, and I normally
use a 2.5% solution but with the 25% that the Formulary sells, I take a ml
out of the bottle, immediately put it in a thermos of 1 liter of gelatin,
and keep that capped at all times, pouring out 1/2 c. at a time. He was
talking about 40% to 40% (or 37% as formalin is) and the most important
thing here is that formalin is a gas at room temp. I can also locate my
notes from Ryuji but he may chime in without my having to do that.

"Whence, it seems from the LD50 (lethal dose, 50% rat population) values,
that glutaraldehyde is about six times more toxic than formaldehyde *on a
weight basis*. This is generally born out by the recommended Occupational
Exposure Limits, which is about four times lower for glutaraldehyde -
on a weight basis.

Set against this is the fact that formaldehyde is a known carcinogen in
animals but glutaraldehyde is not known to be.

Both substances are said to have "reproductive effects" i.e. may be
teratogenic or mutagenic. (Pregnant students keep away!)

But the toxicity measurement per unit weight gives you no idea of the
relative risk in practice, which also depends on the amount of substance
that might be ingested/absorbed/inhaled:-

Let's suppose no-one is going to drink the hardener baths - that's a short
road to a painful death.
Let's further suppose that gloves and labcoat will always be worn and a
face-mask if needbe with the concentrated solutions, so there is no
possibility of skin contact with the solutions.

Then the only risk comes from *inhalation of the vapours*.
The relative risks here could be very different - and much less for
glutaraldehyde - because of their differing physical properties.

Both substances are usually supplied as 40% solutions in water (tho' you
well dilute them 10x ? for use as hardeners). But this is where I run out
data - I don't know the vapour pressures of these substances over their
aqueous solutions, but they must be very different:

formaldehyde (pure) is a *gas* at room temperature, Boiling Point -21 C

glutaraldehyde (pure) is a rather involatile liquid, Boiling point +187 C

so glutaraldehyde is far less volatile, and its solution will have a much
lower vapour pressure over it than formaldehyde - so far less is likely to
be inhaled. Just the 'smells' are an indicator. Sorry I can't quantify it.

What I'm saying is:

1) The higher intrinsic toxicity of glutaraldehyde should not be an
for preferring formaldehyde, because you are likely to inhale much more
formaldehyde than glutaraldehyde - so the toxic effect is comparable or

2) Both substances are toxic enough, in concentrated solution, to require
handling in a fume hood with an adequate air extract system."

----- Original Message ----- From: "Don Sweet" <don@sweetlegal.co.nz>
To: <alt-photo-process-l@usask.ca>
Sent: Sunday, April 06, 2008 7:36 PM
Subject: Re: A few gum things

Let me say first that I have zero technical knowledge or training on this
topic, but I wonder whether there is any real basis for preferring
glutaraldehyde over formaldehyde.

Although g'de is marginally less likely to get up your nose than f'de at
room temperature, it seems just as nasty in almost every other respect. At
least the appalling smell of f'de prompts you to take immediate steps to
protect yourself.

One analysis I found on google suggests the apparent lack of carcinogenic
response to g'de is due to its greater toxicity compared to f'de!

Don Sweet

----- Original Message ----- From: "Christina Z. Anderson"
To: <alt-photo-process-l@usask.ca>
Sent: Monday, April 07, 2008 8:14 AM
Subject: Re: A few gum things

Wpw, Henry,
Thanks for this--I will try the extreme dilution thing asap!

I totally agree about the yellow.  I try to forbid myself from
the yellow layer at night because invariably I wake up the next day and


resultant print turns out too yellow biased. If I err on any layer, it
development of the yellow.

LOL I have to tell you a funny. The first time I taught gum in my alt


a la PDN, the students felt pretty bogged down with curving gum AND


it, and I only had 2 final projects in gum at the end of the class. The
next time I taught gum, I had one non-curved/low tech assignment in gum


then went into gum curves and I had students who really wanted to
monochrome, duotone, tricolor, etc. etc.--in other words, more


SO, this year, I assigned these assignments:  one layer monochrome


gum, duotone uncurved, tricolor uncurved, tricolor curved, and then


curved over cyano. The overwhelming opinion from the students was to


out with correct curves because when they finally got to the curved gum
prints it was infinitely easier to get a good print!

I always learn and morph with my students....next time I will do one


black uncurved monoprint and go right into curves.

Now, some other gum things:

Two, with offlist correspondence a gummist struggled with gum immensely,
specifically the blue layer staining horribly and/or not releasing, and
finally bit the bullet and sized with glutaraldehyde-hardened gelatin.
Presto, perfect gum print first shot. I have had this experience with a
number of offlist gummists. Photographer's Formulary now sells glut,


is at a 25% (!) strength so must be cut down to 2.5%! If used at 25% it
requires less than a ml of that per liter!

I decided this fall/winter to size a bunch of paper a la formaldehyde,
because I really wanted to compare the two (glut and formalin) side by


Hey, formaldehyde works great. I sized my paper with gelatin inside,
went out into my garage and hardened in a bath of 100ml formalin to a


water. Hung all my papers to dry out there. When fairly dry, I brought


the sheets inside the house and hung them in the bathroom. I was not
prepared for what happened.

My garage was about 40 or so degrees. My bathroom was 70. The formalin
outgassed horribly, so bad that I had to slam shut the bathroom door and


enter because my eyes stung horribly. Glut does NOT outgas at that low
temp. Another plus for glut!

Well, it wasn't a question of not entering the bathroom again. I
the door shut so hard the doorknob locked on me and I could not get the


open even with picks and screwdrivers and wrenches so my son in law had
come over and remove the door handle and replace it. By that time all
outgassing was past.

----- Original Message ----- From: "Henry Rattle"
To: <alt-photo-process-l@usask.ca>
Sent: Sunday, April 06, 2008 11:41 AM
Subject: A few gum things

Over the past month or two, Iıve been working through the PDN process
tricolour gum (for the second time, but this time doing it properly, and
avoiding ³shortcuts² that turned into dead ends). I really enjoyed the


of PDN and the way it makes you look at every step of your working
procedures, and also the fact that it actually works!

On the way I learned a few things which most of you probably know, but


be of some use to someone. Here they are:

1. Thereıs a use for that long-neglected darkroom masking frame - itıs
perfect for holding paper flat for brush coating.

2. Donıt develop and clear gum, especially yellow, by the light of a
low-energy compact fluorescent bulb! One evening I ³cleared² a yellow
pigment layer in a room lit by an energy-saving bulb. Next morning, by
daylight, the pigment layer was all still there! I looked up the
spectrum of these bulbs. There are spikes and gaps in the spectrum
everywhere - (see for example
http://beale.best.vwh.net/measure/cf-spectrum/index.html, or
http://home.freeuk.com/m.gavin/grism2.htm). These lamps emit blue, green


red wavelengths, but in particular there is almost no yellow. I should


known this - I studied physics - but experience is a better teacher...

3. The best way for me to clear a gum print in a reasonably repeatable
controllable way is to use a gardenerıs hand-held spray-mist (thank you,

4. For tricolour prints using gum over cyanotype, Iıve found that
traditional cyanotype, used at full strength, is just too strong a


balance with watercolour pigments. However it works fine if you dilute
Diluting 1 ml of (A+B) with between 5 and 7 ml of deionised water gives
good medium blue. Once diluted, it needs less exposure than
(1+7 was 2 stops faster than full-strength A+B) and it also needs a
significantly different PDN curve. (Again, thanks Christine for offline

With best wishes


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