The silver electrode should be solid silver. I have a batch of them here that I made by hand. I used 12 gauge silver wire 99.99% pure. It should be plated with the salt which represents the major constituent of the emulsion. Use a reference electrode of Ag/AgCl in all cases. However, use of a bridge is advised due to Cl leakage from the electrode. The book contains photos and a description of the procedures. Much of that is posted here in less detail.