Measuring vAg - preliminary results!
One of the unstated goals of the book has been to supply the reader with a simple and inexpensive method to measure vAg. This is critical in double run emulsions, in order to know where you are in the grand scheme of things making a particular crystal.
I have been working on this for nearly a year now, and have been able to make my first measurement of vAg today. If things work out, then I have made a major step forward for the craft of emulsion making, and I can reduce it to about 3 simple parts for the experimenter.
Right now, I have a breadboard with pieces all over the benchtop, and the readings are erratic, but the general error with 1 M NaBr is on the order of 6 millivolts which is not bad for the first "real" setup. The error becomes larger with greater dilution. That is what I face right now.
I would like to thank Kirk Keyes, Jim Browning and Bud Wilson for help and support in this. Without their expert opinions and help, this preliminary result would not have been possible.
Give me some time to think on the problems and get feedback and I'll try to get better results.
On a separate note..... Why am I doing this?
To answer my own question, I am trying to get to the point where I can make a graded Iodide core/shell emulsion. To do this, I need to hold the vAg constant while reducing Iodide from 100% to 0% leaving an emulsion that is 100% at the core and 0% at the surface (for all practical purposes) and which is about 10% overall Iodide.
To do this, I need to maintain a constant vAg or a known vAg for most of the make.
I also need to use up to 4 input jets with 3 of them salt.
This is going to be fun. :(
What I mean by "creating photographic materials for practical use"
I understand well that there are many "alternative processes" that are easy and affordable ---, but they don't give enough speed or sensitivity to be of a practical use.
On the other hand, there are many very practical (for end user) "processes" like CCD chips, but they are impossible to create at home ;).
But, this silver-based emulsion making has proven it's practicalness by being in daily use even today by millions of enthusiasts and even complete laymen, and still, it is somehow possible enough for one to do at home if given enough interest and time to learn the process.
Fictional situation: in 2030, there are less and less films to choose from, and people are uncertain how long they will be available.... If I could say: here I have a home-made 400-speed BW film with nice tone rendition and manageable grain and sharpness, and paper to print it to with nice results, I'm sure there would be many who would like to try it out - and learn the process how to do it!