From: Peter Fredrik (pete@fotem.demon.co.uk)
Date: 02/04/01-01:38:18 AM Z
> Dave Rose wrote --:
>
> As for heating the print, or moistening it (to achieve accurate
> re-registration), I've always done this very slowly and carefully. Yes, it
> is possible to ruin a print if the emulsion is 'overheated' or if the paper
> is unevenly or excessively moistened. But the alternative (not doing it and
> suffering from poor registration) is unacceptable (for me at least). One of
> my goals with gum printing has been to capture detail as clearly as
> possible. (Since I use a 4x5 view camera, I can't get away from that
> mindset).
Hi Dave,
Your point about stretching and shrinking is an interesting one. I did some
tests a few years ago to see what happens to a piece of rag paper when
submitted to a soaking and drying regime. What actually happens when one soaks
it in cold water and dries repeating this action over and over again? How does
this expansion and contraction change paper size?
Well this is what happened to a sheet of Fabriano Artistico fina 200gms that
was given this treatment
A sheet of paper was 9.50inches long by 4.00inches wide in size was used. A
line was drawn at the top, in the middle, and at the bottom, with a pencil.
This paper is cut in two, and one piece was left as a control
In the first test the second piece of paper was soaked in cold water for 10
mins and dried with a hair dryer.
When it was taken out of the water it had stretched approx. 1/16 inch compared
to the control, on drying it had shrunk 1/ 8inch compared to the control,
In the second test the process was repeated and there was no change in size
In the third test the process was repeated this time there was slightly more
shrinkage. Making the total shrinkage a fat 1/8 inch say 5/32inch
In the fourth test there was no change in size. I did six more tests and there
were no further changes in size. The paper had for all practical purposes
stabilized.
Ok this was all right for Fabriano Artistico fina 200gms, but what about other
paper's did this same rule apply?
So I Continued paper testing this time trying out the following papers
a)Fabriano Artistico 200gsm [control]
b)Ingres Fabriano 90gsm
c)Hammer 4r 180gsm
d)Goldline Lanaaquarlle 185gsm
e)Rives BFK 200gms
f)Hunni 300gms
Each paper sample was soaked in cold water for 10 mins then dried with a hair
dryer. In each case the sample stretched beyond the original size when wet
then shrunk back smaller than the original size when dried, by the following
percentages.
a)0.33% [ control ]
b)1.00%
c)0.33%
d)0.33%
e)0.33%
f)0.33%
Which in the case of a) to f) was the same even though the paper weight was
very different
Although most of the papers seemed to follow a similar pattern, b) was the odd
man out. This paper was very thin and designed to be used as a paper for contie
crayon and chalks not really suitable for our processes it did stabilize but
kept moving around slightly.
Conclusion
Most papers shrank to the same extent independent of paper weight, thinner
papers expand and shrink to a greater extent and are more fragile ,however the
final shrinkage was the same, the thicker papers, which seemed to be more
stable, however thicker papers take longer to dry out, which can cause trouble
through water retention.
Drying is critical as only when the paper is completely dry, does the paper
stabilize. A good method is to dry the paper on a sheet of glass that is cold.
What happens is that as the dryer dries one side the moisture travels through
the sample and creates steam on the other, so keep turning and moving around
until the steam is no longer visible, the sample is then dry and stable.
So Dave if you gave your paper this pre shrink treatment firstly ,you would
not need your paper size adjustment technique with the possible risk of pigment
staining.
Hope this helps
Pete
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