Hi,
I'm new to the forum, having been introduced to it and to Wet Plate by Seán MacKenna in London. I just moved to Lisbon and am starting to attempt to make plates here, using one of Ray's fine 8x10 cameras.

As it happens, there was another photographer here who left to move overseas in a hurry and gave me his chemistry - including about 400g of KCN.

As I have it I thought I'd try it as a fix. My question is how do you dispose of the used KCN fixer solution? I was told slaking it with Copper Sulphate should work. This seems to be something nobody mentions - is that because they pour it into the public sewer on the quiet maybe?

I'd be very interested to hear how people dispose of it if they do use it?

Regards,
Fionnbharr

People get rid of it several ways. One is to pick a quiet patch of weeds and pour it in. Another is to add Hydrogen Peroxide and set it in the sun, converting it into Cyanate, then pouring it in the grass. What was recommended to me was to go outside, and pour in a liter of vinegar and stand upwind. Believe it or not, a chemist friend recommended the latter as being the safest. Weather or not I believe this is still up in the air.
chriso

OK, I found the answer:

[bit.ly]

Potassium Permanganate and Copper Sulphate

Chriso, thanks, I think I'd still use a respirator, I live near the coast and the wind changes fast!

ooohh yeah. Respirator? Shoot, I'd use an assistant. I don't recommend adding acid, it was recommended to me. Personally, I've been storing it, then take it to the waste recycling place on amnesty day.

No, I was only joking! There's a guy in Holland posted (on the apug forum) another chemical route using household bleach and testing the result with an indicator solution. But you still end up with a toxic waste of course. I'll have to find a waste recycling company here who will take it.

Vinegar?

Never heard that as one of the huge NO NOs in wet plate (or anything involving KCn) is getting acid into it.


Id be more content pouring a solution of ferrous sulfate into it. That changes it into potassium ferricyanide, Prussian blue, which is non toxic

*but please dont take my info as word of law on this*

I wonder why you are throwning out the fixer anyway as filtering and replenishment should make it last nearly forever.



Edited 1 time(s). Last edit at 11/13/2010 06:38AM by Ray Morgenweck.

right seems like the best thing to do is treat it like your silver bath. take a hydrometer reading at full strength and then test it and then make a repleneshment solution. maybe?

This is one way.
kch disposal

Im not an expert on the subject but I know Mark Osterman used to teach using it till its dead but now says its not a good idea. Cant tell you why technically though. There is some kind of build up that makes it not good to use if you want archival results. If my plates dont clear in just a few seconds I make new and get rid of it.

KCN fixer can be used over and over, say up to about 70, 5x7 plates or 40, 8x10 plates. Just keep it in the tank and use as needed, or if this is not a sealed tank, pour it into another PLASTIC (non food) bottle marked 'used fixer. KCN - 10% - POISON' Once this fixer takes longer and longer to fix. simply dispose of and use a new mix. Remember that KCN fixer as used in collodion photography is only a 12% concentrate. Somewhat benign compared to your KCN base.

I like this posted video for the most part. I respect Mike Jacobson too and his expert opinion!

[www.youtube.com]

NOTE: Never go beyond this approximate place or recharge the used fix. There is a nasty habit of this fixer, after it becomes exhausted and or more CYN is added to recharge it - That it will fix the plates, BUT a year or so later the plates will turn dark, almost black, even under varnish! I have personally experienced this when I first began some 20 years before. Heartbreaking

Many thanks for all this advice which has given me the confidence to use the KCN in due course.

Someone gave me the 500g which seemed like a good idea at the time but then I got the Fear, but I'm over that now.