silvergum: bleaching?

i'm posting this question here, because i think denise from thelightfarm.com posts here. so she could maybe shed some light on this (or anyone else, who has some experience with the process...)

i haven't done any silvergum (yet... it's a very appealing technique for me), but i've done some gum over vandyke prints lately. much to my regret, i had to learn that dichromate is a bleach for silver nitrate (i knew that before, but didn't think of it before trying). gum over van-d can be done, but one has to accept a pretty big loss in density of the van-d layer- mine went from a nut brown to a yellowy ochre.
denise's prints don't seem to suffer from this kind of bleaching and she uses silver nitrate emulsions too. how are you doing this? is a gelatin-silver emulsion less likely to bleach than other silver nitrate emulsions (like van-d, kallitype, ...)?
or are you getting some bleaching action too (and you're very good at hiding it)?
normally i'd try to protect the silver nitrate layer with a coat of something like acrylic medium or so, but the gum process doesn't like most of these things and will react with flaking. a layer of dichromate-hardened gum could be worth a try.

regards and many thanks
pritz

Phritz,

a) Have you tried to tone your vandykes with gold, platinum or palladium? It's not that much expensive...
b) Have you tried to put a layer of hardened gelatin over the vandyke before doing the gum layer?
c) BTW, gumover cyanotypes are nice too; if you choose the correct colors you can get rid of most of the cyan/blue if you don't like it...

Vandyke would be far more vulnerable than Denise's silver print because;
1. The silver grains are much more smaller, because it's a print out process whereas denise's emulsions are develop out
2. The silver image is directly in contact with the environment whereas with the other paper(s) the image is inside a gelatin layer

I would go for (a) or (c)...

Hope this helps,
Loris.

merhaba loris,

i've been using only untoned vandykies so far, i know toned is the way to go, but i only have selenium and (old) viradon around. i recently had to re-stock my chemistry cabinet, so i don't really have the cash for precious metals right now. i could get a bottle of ordinary gold toner, but i've heard it's not recommended for alt. processes use.

i assumed that a silver-gelatin emulsion would be more resistant to bleaching than one without, but using saturated dichromate (like i do. maybe using a weaker solution of dichromate is the key?), i'd still expect to see some bleaching. i didn't know there was a difference in the silver between print-out and develop-out provesses. i've done gum over cyano and it is great (and i do like blue... sometimes), but in this case i wanted to keep the original tone of the image and use gum to deepen the shadows.
here are two pictures: the first one is a gum over vd, that came out rather well. it still has the pleasing brown of the vd and the added gum layer added some depth in the shadows.
the second one is a part of an image where the gum layer didn't work and i washed it off to do it again. this was how i discovered, that the vd-layer changes under the gum emulsion. the emulsion was on the print for about 24h before processing.

pic 1
pic 2

my next step will be trying to add some kind of protective layer: either hardened (dichromate or chrome alum) gum or gelatine.

Hi again Phritz,

If you only want to deepen the shadows then toning is the way to go. Gold toning will slightly cool the image and deepen the shadows considerably, palladium or platinum toning is similar. Each will give different results depending on toning time/activity. You'll get the needed result much faster and the image will be sharper. I notice slight misregistration in the first sample you provide - this is almost inevitable with gumovers; to eliminate or lessen registration errors you have to shrink the paper and size before printing... Maybe the toner solutions are relatively expensive but when you consider the time you'll going to spend for shrinking/sizing and gum printing it will pay for itself.

BTW, you can mix your own gold toner pretty easily. See gold-thiourea toner in Wynn White's Vandyke of Sandy King's Kallitype articles @ unblinkingeye.com site. Try to find someone who does gold plating near you in order to get gold salt for good prices; you don't need the exact AuCl3 compound for the job. I use KAuCl4 purchased from gold plater. It's cheap enough if you can find it. (0.5g is enough for 1000ml toner!)

Regards,
Loris.

hi loris,
do you have to see everything?!? do you mean the grass in the front or the slight halo around the stone? i normally do pre-shrink my paper for gum, but i guess not this time, because the print was from the first batch of vandykies i ever did. the grass in the front is a little out of registration and the area is also a little out of focus in the negative, so it's a combination of the two. the halo- i don't know where that comes from, but it's not registration.

i couldn't really find gold chloride anywhere. except from moersch, but it costs 60 euro per gram (if my math is correct - 15 euro for 25ml of a 1% solution). asking a gold plater is a good idea, i'll check if there is a business like that around here.
but toning is one thing and it's definitely the gum-over i'm interested in. i like the possibilities of variation and also the deep and thick blacks.
i've been only doing gum and carbon so far and i'm trying silver-nitrate alt. processes for the first time these days. i got half a pound of silver nitrate cheaply through ebay. now i'm all psyched for playing around with the various combinations possible with these processes. gum-overs are something that i kept thinking about, ever since i started printing gum.

thanks for the pointers,
phritz

Hi phritz,

I'm just back from a week in Santa Fe for APIS (Alternative Photographic International Symposium, hosted by Bostick and Sullivan). It's a great event and great people. I highly recommend attending next time it comes around.

Silvergum has digi elements to it, so I won't go into things here. I have the materials for a whole chapter on the silvergum process ready to post on TLF right after I get back from three trips in the next couple of months. Until then, I'll be happy to talk you through anything giving you problems. If you can make it to UW Vancouver the second weekend in September, I'll be there discussing the process.

Email me at editor@thelightfarm.com.

Best of luck and fun,
d