Van Dyke Brown precipitate

[Jack Lusted]

Hi All,
Decided to give VDB printing a go. Mixed up the three solutions, then added the first two together, then (as per directions) added the AgNO3 carefully, a little at a time stirring constantly. All fine until (literally) the last drop, then a filthy precipitate came out of the solution.
Now, should this have happened? Is all lost, chuck the muck and start again, or will it be ok? or should it have done this any way?

A brief, knowledgeable word is all I ask.

Jack

[Barry]

I'm afraid its been a long time since I made up any VDB chemicals so I'm not sure if this is a problem I would not discard them and would give them a try. I hope someone with recent experience comes along with a more helpful reply. Nice process.

[Michael]

Jack, I think Martin Reed will know about this, as the process is described in Spirits of salts (pp 63 ff). If he doesn't respond here, you could always pm him.

[Jack Lusted]

Well, after having given the mixture a few days to ripen I coated some paper and it worked beautifully. So don't worry about the precipitate, just filter it off.

Interesting process, but what do I prefer, salted paper or VDB?

Jack

[Dave miller]

Originally Posted by Jack Lusted

Interesting process, but what do I prefer, salted paper or VDB?

Jack

When you have decided then please let us know, preferably with a few posted examples.

[Akki14]

I had the exact same problem. I had red it was a problem but I just leave that fluffy curdled milk stuff in by shaking the bottle before use. It's weird stuff but as long as you were adding it slowly it shouldn't be so much precipitate I think.

Actually I seem to recall if you add in more tartaric acid it might help a little but I also seem to recall I did that to my batch to try to make it more black (it doesn't really help that much).

Ahha! I was right
http://www.apug.org/forums/forum42/3...ecipitate.html

I can't remember exactly the formula now, though... I think I just kept adding in 1g amounts, shake, inspect, add another 1g.... I seem to recall you can do something silly like add up to 10-20g more but that might be too extreme.... Might be something around 10g. I'm assuming that was for 100ml of solution. and I used the first VDB formula on this page
http://www.alternativephotography.co...ype-argyrotype

My solution is so old now the last time I looked at it, the silver was plating the inside of the glass beer bottle :O I don't like seeing that (expensive!) but it still worked too. Stuff seems to last forever in a dark bottle kept in a dark box.

[Akki14]

Oh yeah! I remember now, there's something about gently warming the solution too to get the precipitate to go back into solution (while you're adding the tartaric acid).

I think I mixed my solution about 2 years ago, sorry it's only slowly coming back to me