[alt-photo] Fumed Silica - first impressions/first problems

[Jon Reid]

Hi all,
I posted this to an ongoing APUG thread but thought I would also share
it here too. Apologies if you see it twice. Apologies also if the
small attachment is contrary to list rules.

I used the wet version as supplied by Bostick + Sullivan.
I first printed an image on Arches Platine (the paper I am using
somewhat reluctantly for a large ongoing project) without using any
fumed silica. Once I got an acceptable image I coated another piece
with fumed silica by way of a coating rod (same as I coat sensitiser
with). As a starting point I used 12 drops of fumed silica over an
area about 6x8 inches (for neg size 5x7).

The coating went fairly well, except that I couldn't see anything. By
looking at an angle I was able to determine what was wet and what was
not. Three or four passes max and it looked like a good even coating.
The paper was let sit for a few minutes then dried with a cool blow
dryer.

I then coated and exposed the paper exactly as for the previous print.
As per expectations I observed an increase in Dmax, a slight overall
contrast increase (though less than I had expected). So it all seemed
good. Who wouldn't want more Dmax with Platine, although I agree with
someone else's comment (can't remember whose) about the extra
highlight contrast being undesirable in some images. I did notice some
of what I think Loris Medici is referring to when she says "raised
nap" in the paper, although I've always found this to a degree with
Platine and sometimes 'spot it' in darker areas.

I then tried another negative (4x5) and got very similar results
although I noticed that an uneven coating of fumed silica obviously
results in patches or streaks of uneven Dmax, which looks crap.

I then tried another paper that a friend had been told worked well for
platinum. He had never tried it so I took one for the team. Strathmore
500 series plate finish. Quite thin, about 120-130gsm I imagine. Not
quite as white as platine but with a smoother finish. The first sheet
creased from being too wet. I halved the drop count and coated again.

This is where it gets interesting, and frustrating. The first two
prints, barring a few small areas of patchy Dmax, were stunning. The
Dmax was as good as Platine or better, low-tone separation and
mid-tone contrast were better, and the image was sharper with no
raised nap. It made the print on platine look quite ordinary.

Then, to overcome the patchiness in the fumed silica coat my friend
(Gordon Undy) suggested we coat the whole sheet. We did so, and it did
not crease as it was all wet, rather than a wet area in an otherwise
dry sheet.

This print looked terrible. There was barely a latent image, and when
developed it looked flat and underexposed by about 3 stops. I figured
I must have stuffed up the mix and tried again.

The next three prints were all the same, flat, pale and lifeless. Was
it coating the whole sheet? One last print where I coated just around
the image area as before. Slightly better result, see attached image.
The earlier print is on the right, the problem print on the left. Same
mix, same chemistry, same exposure unit and time, same developer. It's
got me buggered. Since drying the dud print also has a distinctly
powdery feel to it which is absent on the other prints. My apologies
for the crappy phone pics, my scanner is packed away due to
renovations.

I didn't get time to re-try with Platine to check my process and I'm
dumbfounded as to what changed. If it were repeatable the results I
got on the Strathmore paper with fumed silica would force me to
consider re-printing my whole show.

Also, with regard to a patchy undercoat of fumed silica, has anyone
tried adding the fumed silica to the sensitizer mix so it all goes on
at once?

Jon