All tests conducted on Fabriano 5 300 gsm and Bockingford 140 lb paper
which I find does not need pre stretching.
1 No size
Works well for up to five coats. Increasing risk of degradation of the
highlights after five coats or more. Generally speaking one can obtain a
good contrast range multicolour print with onl;y three coats.
2. Formaldehyde hardened 2% gelatine.Worked well . The inference is that
with other papers than then above a hardened size is an advantage.
3.Dichromate hardened gum size (pterotype :-) ). Effective but fiddly.
4.One per cent unhardened size between coats. Works well with no
degradation.
5. Dichromate hardened acrylic/ Gloy mix works well giving a smoth surface
On the basis of these tests my own practice will vary according according
to the image, paper or negative and the tactility required in the final
print.
>Message text written by Judy Seigel
>
>If you are reading this message, hooray. And heartfelt thanks to those who
>noticed what I had failed to -- a 1 is not an l.
It printed out on my machine as 1 . I was surprised to be told that it was
an 'l' which certainly look different,
>Steve & Gord, prayers, thanks, sympathy, and the thought that 1100 bounced
>messages might make it to the Guiness book of records?
Why does it seem to be Daemon that causes the bother apart somebody with a
full mailbox ?
>Meanwhile, a friend has asked for my comments about his near-gum-printing
>experiences. I thought these might usefully be made to the group, where
>perhaps others will have further insights...
>> ---cut--- ...gum-14. Been using equal parts gum and dichromate. Was not
>> using a foam brush for application. Been using a hake brush and having
.> difficulty getting an even coating. Now the big question. How much
>> pigment (in grams) to how much gum (in cc)? I suspect I am using too
>> much pigment because my exposures are more like 30 min. with a FL source
>> that will print cyanotype in 3 min.
Working in this way just leads to difficulties. If you mix your colours on
a plate with the gum first so that you can see the consistency of the mix
from shadows to highlights, you will nt have to weigh the pigment. Try
using a water-colour laquer brush which is designed for coating gum onto
paper.
>
>Generally, with my light sources, a made-for-gum negative takes about a
>third as long to print as cyanotype. However, if you're using the same
>negative that you use for cyanotype, it could be too contrasty for gum and
>hence slow you down --
Vary the exposure according to the partof the density range of the negative
you are trying to print from. For the highlights the exposure should be
about half required for a cyanotype and for the highlights about a tenth.
>Which dichromate are you using? Potassium di, only 10% concentration,
>is significantly slower than ammonium di at 30% concentration.... (can
>anyone do the math on this? ie., how many times *slower* the k di is?)
10 into 30 goes three.
.
As for the "correct" ratio of pigment to gum:
>The short answer is as much as you can pile in until the emulsion flakes
>off instead of making a continuous tone, that is, IF YOU WANT TO DO ONE
>COAT GUM AND DON'T MIND JERKY HIGHLIGHTS.
That is if you want to do one coat gum.
>If you want nice smooth
>highlights without brushing, the amount of pigment can only be determined
>by testing each individual pigment *UNDER A 21-STEP*.
If you follow the suggested method above testing of this kind is
unnecessary. Just remember that the higher the reflectivity of the pigment,
the more you will need. So use strong colours to reduce the amount of
pigment required.
>That's not just the color in question, because the covering power of
>pigments and the difficulty with which UV light penetrates each varies,
>but each manufacturer's version of the color may be different.
That is why it is better to stick with the products of an established
manufacturer such as Winsor & Newton.
>So you look at the test PRINT, and here, trust me, a 21-step tells you SO
>much more than just your regular old negative.
For multi colour printing I remain unconvinced that using a step wedge
tells youanything at all.
> Notice how many steps of
>tone (the denser the pigment the fewer the steps, all other things being
>equal) and how smoooooth and long-scale the highlights are.
If you expose for the highlights with a little pigment you will get the
range but when you are using more pigment for the mid tones and the shadows
you need a shorter range.
>As noted, the first manifestation of over-pigmentation is likely to be
>highlights flaking off.
Or the shadows.
> An option here of course is blasting the emulsion
>with light, way overexposing for an ordinary automatic-development print,
>and then BRUSHING OFF to reveal the picture.
Never include more pigment than you need. Brushing is for controlling what
you want to remove not as an escape route for mistakes.
>That way, you can use a
>humongous over-load of pigment and still get a semblance of continuous
>tone -- although the highlights will be very *GRAINY*. (Brushing takes the
>pigment off the peaks of the paper, leaves it in the valleys.)
Not if you use a hake brush delicately. Nor if you use a hot pressed paper.
>Normally, you don't get near as many steps with heavy pigment -- the sheer
>amount of color stacks up in the bottom register, making all look the
>same, as well as cutting off tones at the other end because light doesn't
>get through the heavy coat.
That is one of the isadvantages of the one coat method.
>And did I say different colors have different sensitivity to light....?
It isnotso much the colour but the reflectivity that affects the issue.
>So, by the way, do different gums. I've tested a half-dozen gums and find
>differences of "speed" by 100% or more among them. My first hypothesis is
>that that's a factor of pH, the more *acid* being faster (uh oh, or was
>that the other way around? got to check the file) but there are many other
>variables; that's just a preliminary hunch....
Again be consistent . Make up your own gum from a reliable source or use
Gloy.
>But you want a ballpark figure: I seem to use more pigment than other
>people. My series with Rowney Jet black gouache used maybe .8 g black and
>from .5 to .7 g other pigments in 10 to 11 cc total emulsion (gum, am di &
>usually water, because my gum is very thick). But note that some colors
>like thalo blue and indigo are very intense & you'd use less of them.
Using the water-colour tradition of using transparent colours working from
light to dark, I would not use gouache as it is designed to be opaque. I
advise against using black wherever possible.
>> (Oh, and do you use cold water or warm?)
>
>My "normal" development is cold water (ie., available temperature), with
>warm water as a fall-back. I haven't tested this AT ALL, but my sense of
>the situation is that warm water would lose delicacy in the highlights,
>all other things being equal (which they so rarely are)....
This is a very effective approach. Use the warm water as a means of
speeding things up or for differential development.
>For applying the emulsion, a foam applicator is best (wastes the least),
>but you have to follow with a whisking smooth with a DRY hake brush (for
>which reason it's handy to have several for a day's printing). Some folks
>on the list have said they use a Daniel Smith "elephant brush," which is a
>much coarser bristle, for that. My experience suggests that might grind
>the emulsion into the paper (or some papers) too much, ie., lead to
>staining -- or at least this semester when some students got heavy
staining, I told them to lay off that kind of brush & staining went away.
My experience is that a lacquer brush wastes least and lasts longer; it can
be used for application and then 'con brio ma gentilamente' to smooth out
the surface. If you do not use too much pigment, a hake brush will work
well for both. Some students have been using brushes with polypropelene
bristles which seemed to work well.
My comments reflect a different approach to gum printing from that of Judy.
Our approaches produce pictures that look different. Neither approach is
exclusively 'right' or 'wrong'. One of the joys of gum printing is that it
allows this flexibility of approach.
Extending Judy's punning title one might think more of 'gum lore' than 'gum
law'.
Which reminds me that soon in this country it will be illegal for a private
citizen to own a working hand gun.
Terry
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