U of S | Mailing List Archive | alt-photo-process-l | Re: Unknown areas in Gum printing?, etc.

Re: Unknown areas in Gum printing?, etc.

In NYC formaldyhde is available in 1 liter size from pharmacy, but requires prescription... do you have a friendly doctor or mortician?

As for gum + dichromate as hardener, I've tried it carefully, as have others. IMO its a PITA... very difficult or impossible to remove all subsequent tone, and has a different effect as base for print.

In the matter of exposure -- with a digital neg, mine are 1 minute.

And in the US, you can buy glyoxal from Artcraft.


On Fri, 27 Apr 2007, kerik@kerik.com wrote:

Yes, you probably don't want 5L of formaldehyde. I was able to get a 1-pint
bottle from a local pharmacy. Perhaps you could try that?


Original Message:
From: Jacek gonsaj@iinet.net.au
Date: Fri, 27 Apr 2007 15:59:39 +0800
To: alt-photo-process-l@usask.ca
Subject: Re: Unknown area in Gum printing?


Thanks for that. I have to readjust how I brush the coating. Change the
pigment concentration and get some hardening. The hardener, I just spent a
whole lot of time sourcing it and came up with only one company only
selling 5 litres of formaldehyde and nothing less, one of the reasons I'm
reluctant to get it. I cant even get it from overstate or overseas with all
the security regulations :| Though I havent looked for others like Chrome
alum or glyoxal, I think its best if I do.
Cheers guys.

On Fri Apr 27  3:04 , Katharine Thayer <kthayer@pacifier.com> sent:

Jacek, this is way underpigmented for lamp black, so as I guessed
earlier, pigment stain due to overpigmentation is definitely not your
problem here, as you might have seen if you'd checked the comparison
images I pointed to for lamp black.   I'd agree with Judy;  your
stain in highlight areas (and I'd definitely call that pigment stain
in the highlights on the Arches)  is probably a function of the
unhardened size.  It's interesting that the unhardened gelatin seems
to work better on the Fabriano paper.  I agree that tray clearing is
probably better than spraying the clearing agent on.

On Apr 26, 2007, at 10:32 AM, Jacek wrote:

Hi all,

If you want me to upload more detailed images of each let me know.
The negative is made by an imagesetter, I used a 2% increment grey
scale file made in photoshop.

This is the Arches w/c 300gsm smooth paper.
Print looks very light.

The first one, 4min, its a bit messy with me adding a clip on left,
in the middle of the paper when I had to dry it, it took some w/c
out :|
The numbers can be distinguished.
16to20% above it, not so sure what I did there possibly sprayed the
potassium Metabisulfite a bit too close?
0 to 30% seem fine to me, though after that things start looking
messy, there seems to be a vertical light smudging, plus yellowing
from 86% to 100%, possibly needs more potassium metabisulfite.

The next, 6 mins.
The print start looking smudgy at 52% onwards. Perhaps too much
yellowing from the dichromate stain?
The bottom 92% onwards was at the edge of the paper and there
probably wasnt enough coating there, thats why it looks uncoated
and speckly.

The next 8 mins.
The clips there again in the middle :|
You can clearly see that with more time, the 10% is darker than the
4mins one.
Same sort of vertical yellow streaking/smudging in the shadows.

Next image:
Fabriano Acquarello 300gsm

First one, 8min.
The clip smudged the paper in the middle?
From 0 to 40% it looks ok.
Then It starts getting discoloured after that, with yellowing on
the print. The scan your looking at doesnt seem to represent in
colour to what the print does.

The next, 12min
This seems to look ok from 0 to 32%. From there it looks dark and


The colour doesnt seem to be constant in the shadows. It has
streaks of lighter tones?
I think I could be overexposing too much?
Possibly need to add more gum?

Relative humidity is 60%-65%, Black Light Blue tubes 18 watts.

Thanks everyone for the help, I appreciate it! :)

 On Thu Apr 26 21:11 , Katharine Thayer kthayer@pacifier.com> sent:

Hi Jacek,
One initial observation is that pigment stain will affect the
highlights and unexposed areas of the paper as well as the shadows,
so if your highlights and the unexposed parts of coated areas are
clear, then pigment stain probably isn't an issue.  And from the
description ("a small smudge") of the amount of lamp black you used,
it seems unlikely that overpigmentation is an issue either.  The
pictures will help a lot, so I'll reserve further comment til you can
upload them, thanks,

What are you using as a light source?  What's your ambient humidity

On Apr 25, 2007, at 11:24 PM, Jacek wrote:

Hi all,

I tried my second attempt. Just a basic outline first on what I did.
Arches smooth 300gsm and Fabriano Acquarello 300gsm

1. boiling water pre shrinked for 10mins. Dried for a day.( no more
speckles in the Arches)
2.Gelatin 3g to 500ml, cold water for 10 mins... Heated to 43
degree Celsius.
3.Added paper to the tray of gelatin for a minute, took excess
gelatin off by sliding the paper on the side of the tray. Dried for
the day. Stored the same Gelatin in the fridge
4.Reheated the gelatin the next day. Recoated the paper the same
way. Dried.
Didnt add any hardner as yet, as I cant seem to get time to go buy
any! :)

5ml 13% Pot Dich + 5ml Gum 35% + Windsor&Newton LAMP BLACK a very
SMALL smudge! (coudnt get any Ivory black as yet, will do so..)

Coated paper, fan dried for 15mins.
Added a negative with squares 2% increments made in photoshop from
white to black. Each 2% square has a number on it, which should
clearly be seen when printed.

The sheet of Arches had 3 of the same negatives on it, each exposed
4, 6, and 8 mins. Just covered each negative when it passed the min

Developed for 5 mins face down in room temp water.
Next tray developed for 5 mins face down in room temp water.
Next tray developed for 20mins same room temp water.

On the Arches paper I got:
What I got was NO staining in highlights or midtones or the whole
paper. They looked ok though a little on the light side the tones
came up.
Can read all the incremented 2% numbers in those areas.

The shadows are another business altogether, what I got was a
massive yellow staining probably from the dichromate, plus it
looked like a real mess as I couldnt really make out the
incremental numbers from the negative. The mess seemed like too
much watercolour overpigmented, its not one colour but just smudges
of watercolour and yellow staining.
Reading Katharine suggestions, I'm thinking what I'm looking at
could be OVERexposure? or the small Smudge I used from the lamp
black is still too much pigment!?
I doubt it was caused by overcoating, as I turned each of the 3
negs upside down side by side, got the same result on each part of
the print.
Could it be my sizing, and not using a hardner? Though the
Highlights and Midtones look good?

I got kind of fed up looking at the yellow staining and used a 5%
potassium metabisulfite solution, sprayed with a hand held spray
gun. Didnt work as well, next time i'll use a tray bath.

The other Fabriano Aquarello paper I'll add more info on it later
can't recall what it looked like, but had the same sort of problems
as above.

I'll scan the prints when I get home and upload to a website.


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