Re: A few gum things
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)
that glutaraldehyde is about six times more toxic than formaldehyde
weight basis*. This is generally born out by the recommended
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 lab
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
that might be ingested/absorbed/inhaled:-
Let's suppose no-one is going to drink the hardener baths - that's
road to a painful death.
Let's further suppose that gloves and labcoat will always be worn
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 may
well dilute them 10x ? for use as hardeners). But this is where I
run out of
data - I don't know the vapour pressures of these substances over
aqueous solutions, but they must be very different:
formaldehyde (pure) is a *gas* at room temperature, Boiling Point
glutaraldehyde (pure) is a rather involatile liquid, Boiling point
so glutaraldehyde is far less volatile, and its solution will have
lower vapour pressure over it than formaldehyde - so far less is
be inhaled. Just the 'smells' are an indicator. Sorry I can't
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
formaldehyde than glutaraldehyde - so the toxic effect is
2) Both substances are toxic enough, in concentrated solution, to
handling in a fume hood with an adequate air extract system."
----- Original Message ----- From: "Don Sweet" <email@example.com>
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
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
room temperature, it seems just as nasty in almost every other
least the appalling smell of f'de prompts you to take immediate
One analysis I found on google suggests the apparent lack of
response to g'de is due to its greater toxicity compared to f'de!
----- Original Message ----- From: "Christina Z. Anderson"
Sent: Monday, April 07, 2008 8:14 AM
Subject: Re: A few gum things
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
resultant print turns out too yellow biased. If I err on any
layer, it is
development of the yellow.
LOL I have to tell you a funny. The first time I taught gum in my
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
next time I taught gum, I had one non-curved/low tech assignment
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
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
specifically the blue layer staining horribly and/or not
finally bit the bullet and sized with glutaraldehyde-hardened
Presto, perfect gum print first shot. I have had this experience
number of offlist gummists. Photographer's Formulary now sells
is at a 25% (!) strength so must be cut down to 2.5%! If used at
requires less than a ml of that per liter!
I decided this fall/winter to size a bunch of paper a la
because I really wanted to compare the two (glut and formalin)
Hey, formaldehyde works great. I sized my paper with gelatin
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
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
outgassed horribly, so bad that I had to slam shut the bathroom
enter because my eyes stung horribly. Glut does NOT outgas at
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
open even with picks and screwdrivers and wrenches so my son in
law had to
come over and remove the door handle and replace it. By that time
outgassing was past.
----- Original Message ----- From: "Henry Rattle"
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
tricolour gum (for the second time, but this time doing it
avoiding ³shortcuts² that turned into dead ends). I really enjoyed
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,
be of some use to someone. Here they are:
1. Thereıs a use for that long-neglected darkroom masking frame -
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
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://home.freeuk.com/m.gavin/grism2.htm). These lamps emit blue,
red wavelengths, but in particular there is almost no yellow. I
known this - I studied physics - but experience is a better
3. The best way for me to clear a gum print in a reasonably
controllable way is to use a gardenerıs hand-held spray-mist
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
Diluting 1 ml of (A+B) with between 5 and 7 ml of deionised water
good medium blue. Once diluted, it needs less exposure than full-
(1+7 was 2 stops faster than full-strength A+B) and it also needs a
significantly different PDN curve. (Again, thanks Christine for
With best wishes