Taking a leap into emulsion making

[Photo Engineer]

Salt and VanDyke do not need a gap.

 

[pdeeh]

Better still!

 

[NedL]

OK since this thread took a turn in that direction, I have questions too.

When I make a salt print, with some gelatin added, am I getting "close" to making an emulsion? I've been playing with about 0.6% gelatin, but I've seen salt printing recipes with up to about 3%.

Then Liam Lawless' POP recipes are very similar to salt printing recipes, but with more gelatin, getting up to near 5%. These are still printed out of course. He calls them emulsions. The silver nitrate is mixed in before coating, but there is no "washing" step prior to exposure of the paper.

Alan Greene's book has instructions for developed out "salt prints", and the biggest difference seems to be an excess of salt ( whether chloride or bromide ) instead of an excess of silver nitrate used in printing out. His instructions also use small quantities of gelatin.

Then the emulsion making sticky threads here use much more gelatin, and include steps like noodling and washing...

Would you call all of these things emulsion making? Or only the ones that mix the silver nitrate in prior to coating? Only the ones with noodling and ripening? Could you coat a piece of glass with a thinner POP emulsion and print it out instead of developing out, or would the coating simply be too thin and runny?

I think I will be "stuck" at the salt print and calotype stage for a long time to come, since there are about a million details to play around with and I'm enjoying it so much. But I can imagine trying to make emulsion eventually

 

[Photo Engineer]

An emulsion is formed in the presence of gelatin such that the gelatin surrounds and protects the grain that forms. During this process, the grain grows as a salt excess is maintained, until the proper size and shape of grain is obtained. These can be made to have very high speed, pan sensitivity and good keeping.

This process does not happen in any of the other alternative processes and thus you are left with a fixed form of silver salt and a fixed ratio of salt to silver. These processes are very slow and generally only sensitive to blue light or UV radiation. Some are charactarized by poor keeping.

PE

 

[NedL]

Thank you PE that makes sense.

( And yes, the two processes I'm playing with are characterized by extremely poor keeping: my calotypes must be used in less than 24 hours or they fog horribly in the developer, and my salt prints must be made within about a day of sensitizing or they begin to fog. )