Re: haunted GUM (i surrender)
thanks for all the answers and tips. but still no success.
the thing with acidity sounds interesting. i will keep my eyes peeled for anything that could influence the ph-value.
i do have some glutaraldehyde. i bought a bottle of rollei hardener for photo emulsions a while ago. then i did some reading on -aldehydes... i only have one work room and a bathroom for anything photographic, no lab or studio. no balcony or garden. it made me way too nervous with all the outgassing, so i ordered the chrom alum. probably not healthy either, but at least it stays put.
but i will keep it in mind as a last resort.
did someone say mackie lines? got 'em.
i'm pretty much at my wits end (not that this was a long way....) i will give it a break now until next week or so, otherwise i'd start accusing people of putting something in my tap water ... wait! i used distilled. not even that i can do.
so far i've checked the dichromate, used different pigments, fresh gum, different papers (sized, unsized and gesso). checked for contaminated brushes, was extra carefully about unwanted exposure to light....all either show the same results as i've shown before or don't clear at all. only one was a little better, a strip with pot-di, fresh gum and lamp black: the did clear and showed minimal tonal inversion, but still had significant stain (about a zone 5) in the unexposed areas.
i know this must sound unbelievable, but the same material printed fine for me one or two months ago. i don't say it was perfect or absolutely stain free (i'm pretty impatient and quickly start with the brush and flowing water while developing). the test sheet i posted earlier, was the same paper, the same size, lamp black and it was absolutley not tampered with. it shows no tonal inversion (even at 20 seconds) and no stain (except a slight yellowing from the dichromate). most times the emulsion was off rather too quickly than too late.
the only two possibilities left that i can think of are
a) i now dry direclty in front of a (cold) fan. before that i've hung the papers with no fan.
b) i mix the emulsion a little differently. before i'd put the pigment powder, the gum and the dichromate into the mixing bowl and mix it with a little milk frothing propeller for a few seconds. now i put the pigment and the gum into the bowl, mix with a brush until it looks fine, then add dichromate, little more stirring, then coat.
but i can't really see those making a difference.
i will now size some paper, which will take one or two days to harden. i will then make some more tries with sized paper.
gum is the devil
Christina Z. Anderson schrieb: