Barbara,
For what it is worth my comments follow. I'm interested to read what
others on the list have to say!
>Recently I started trying to size paper (BFK) at home with the chrome
>alum/gelatine mixture outlined in the archives. My previous experience with
>gum printing has been on formaldehyde hardened paper in a school setting.
In my experience with Gum this may be your first problem. BFK seems to
lack the toughness necessary for multiple coatings. Try Bockingford,
Saunders waterford, or if you can find it Strathmore watercolour paper
which I used for years with great success.
>After 4 exposures I noticed that the gum/pigment seemed to be sloughing off
>in various areas of the image giving a slightly mottled look.
I have seen it mentioned elsewhere on the list to re-size with gelatin
after each coating. I don't currently do this but not a bad idea, I sure
someone else will post more details on this approach. I have found that
this problem seems more related to the paper you use than the sizing. I
use two gelatin baths, with formalin added to the second bath. I find
that this can hold up for 6-8 coatings on the saunders papers, and a
little more with Bockingford. BFK in my experience seems quite porous to
begin with and it doesn't like all that physical handling either. I have
only used it for single colour gum and Van Dykes. A mottled look can
sometimes be related to an excess of pigment, which can cause a stain
that has a mottled appearance. Is this the kind of look you are talking
about? This stain problem has in my experience been primarily occurring
with either Winsor Blue or Cadmium Yellow.
>
>Also, I noticed that any manipulation with brushes was much more tedious. I
sized
>the paper twice, made sure the humidity wasn't too high when I sized it, and
>did not print on it until 2 days later. Should I add more chrome alum to
>the gelatine
I am just interested in how you found manipulation more tedious? I have
also seen mention that alum should not be used for sizing or clearing as
it can effect the paper permanence. Can any one else confirm this? Or I
am getting confused with something else?
> or maybe size with 3 coatings?
I have tried this and it seems to work well, so I just do an additional
gelatin coat and then add the formalin to the 3rd bath. I have been doing
this recently with my current body of work as I am having a few more
problems with staining than usual.
>Any suggestions on how I can improve my results would be greatly
>appreciated.
Perhaps other people on the list may confirm this but apart from the
prepartion of the paper, and the type you use, the concentration of gum
pigment, and the length of exposure will all have an impact on the things
you mention. So some of the things you can adjust are:
If the gum keeps on coming off during development, perhaps you need to
give more exposure, or it could be related to the coating being too
thick. I have seen the gum/pigment sloughing off in large areas and have
found one solution is to ensure that the coating on the paper is as thin
as possible.
Also watch your Gum/pigment concentration. Too much pigment can cause
staining that has a mottled appearance, and I find that while much of the
coating does wash away, stray pigment remains in the fibres of the paper.
I have found that this is more of a problem with the rougher surfaced
papers like Bockingford cold pressed. Smoother papers like Saunders Hot
pressed doesn't seem to have this same problem.
>
>Sincerely,
>Barbara Dayton
>bdayton96@enter.net
>
Hope this helps some
Cheers
Hamish
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"We have no theology, we have no dogma, we just dance"
Hamish Stewart
Gum Bichromate Photographer
Astrologer
Tarot
http://www.vrx.net.au/ad163/artists/hamishstewart.html
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