Electrode Geometry

This post is to illustrate the effects of different spacing and sizes of electrodes. You will soon get an understanding of the best spacing for your own chosen electrodes, but you should know the principles. All the following “rules” are actually approximations, but you will be able to fine-tune them yourself. This is probably the most important subject to learn once you have mastered the basics.
If you double the size of your electrode, you should be able to double the current. Note that only the side of the anode which faces the cathode should be used to calculate the area. Kephra found that the best results used about 1 ma per square centimetre with the distilled water kept hot, and using a stirrer if possible.
I only use a stirrer if “cooking” cold. I find that the convection currents are adequate to stir the DW, but if you have a stirrer, laboratory or home-made, then use that. More vigorous stirring is better, the idea being to sweep the silver ions away from the anode as fast as possible.
Maximise the anode size, minimise the cathode area. A piece of copper wire, stainless steel or brass is fine, unless the current is set to alternate polarity at intervals.
1 ma per square centimetre of submerged anode area for the suggested current when processing DW hot.
10 ma per square inch of submerged anode area when processing DW hot.
2 or 3 ma per sq inch of anode area when processing cold.
Moving the electrodes closer together increases the amperage (until the set-point of the constant-current circuit is reached).
For a Silver wire anode, 4 inches submerged depth, we suggest no higher current than 3 ma cold and 6 ma hot-processed. 12 gauge wire is 2 mm in diameter.
Remember that the effective area of an anode is that which is facing the cathode (the reverse side has much less effect) and of course, submerged in the DW. Do not allow suspension devices or parts of the holder to touch the DW unless they are made of the same quality of silver as the anode.
If you seem to need a lot of electrolyte and want to use less, increase the size of the electrodes or move them closer together.
If you need to use more electrolyte to prevent cathode plating, raise more of the cathode out of the water, or increase the electrode spacing.
If you are using a circuit with a constant-current limiter, connect a voltmeter across the electrodes and connect an ammeter in series between the positive connector of the PSU and the anode. Once the water is up to the operating temperature, measure the voltage across the electrodes in air.  Submerge the electrode array. Add electrolyte until the voltage starts to drop to about 90 per cent of the original value. This indicates that the constant-current circuit is now operating to control the voltage in order to maintain the current. Note the current. The operating voltage should be as high as reasonably possible, between 20 and 30 volts (at the beginning of the process) is ideal. If possible, maintain the voltage over 10 volts by moving the electrode spacing.
If each drop of Sodium Carbonate makes too big a change in the measured voltage across the electrode array, then dilute the electrolyte and use more drops of a more dilute product.
If you are getting hydrogen and oxygen bubbles coming off the electrodes in any significant quantity, then either the current is too high or stirring is too slow. Increase the speed of the stirrer or use a miniature water pump.
To increase the electrode voltage, reduce the area of the cathode exposed to the water. You can even raise the cathode out of the water so far that the tip of the cathode wire is just touching the water, but ensure that the evaporation of the DW does not leave the cathode out of the water during your production process.
Professional electro-platers use a “dog-bone anode” where the thin edges of the plate are swollen and rounded off, because the electrical field is concentrated at sharp edges. You can see this effect when running with too little electrolyte, as the oxide accumulates on the edges of the strip of Silver. I am unsure whether this would have any significant effect for our application. I personally ignore this effect.