[cameraman]

Originally Posted by caswellsage

no appreciable drop in voltage over any reasonable time

I've noticed that larger surface areas (300-400+ in²) produce curves with appreciable, steady voltage drops.

Originally Posted by caswellsage

I just find it easier (always have) to think about the amp-minutes required to get the job done. No calculators required.

I'm not seeing that. Let's say I want to anodize 223 in² at 9.3 amps. I suppose the 223 * 5 = 1115 is easy enough, but who would want to divide 1115 by 9.3 in his/her head?? The 223 came out of the computer anyway so I'm already sitting there, and I log all of my anodizing runs into the computer. If I have to do that 3 or 4 times to come up with an acceptable anodizing time, forget it - I already used up plenty of brain power designing the 223 in² part.

Originally Posted by caswellsage

Forget the peak voltage thing.

I have to disagree with that sentiment. I know that I'm not going to see the exact same peak voltage as the calculator produces, but I know that it's a guideline that is good within 3-5 volts for my tank. I know that when the voltage is outside that range that it's indicating a problem: too high, my connection is failing. Too low, I'm likely not getting good surface agitation.

You didn't address agitation in your posts. Most of my anodizing has been done at a CD of 4.5 a/ft². Lately I've tried pushing it to 6 a/ft² and have discovered that I quite simply do not have sufficient agitation to pull it off successfully. I shudder to think what kind of agitation I'd have to produce to use a 14.4 a/ft² current density - I have visions of acid splashing out of the tank . The remaining acid would probably fume into the air from the excessive heat generated. I'm not sure I could even do it for irregularly shaped parts, leaving dead zones of dissolution which would defeat both the aesthetic and functional purposes of anodizing in the first place.

Your method causes parts of different size to be anodized at different current densities. You said "current your supply and connections can handle", so knowing that my .045 wire can comfortably handle 2 amps but begins to warm up above that, I'd choose 2 amps for both my 20 in² part and my 30 in² part. The first part would anodize at 14.4 a/ft² and the second at 9.6 a/ft². Since they will have different pore sizes, will they not come out of the dye at different shades? Too close? How about a 60 in² part, at 4.8 a/ft²? If the parts are going different places, fine, no issue, but if the parts will be together making something else, no good.

If your method works for you, great, more power to you, but I'm not seeing any benefit to it and it appears to me that it has the potential to create a slew of problems, especially for someone who doesn't thoroughly understand the process: 2 amps for 20 in² sounds completely reasonable to a new person, but my 10 amp 30 volt supply wouldn't be able to do it - and yet I can do 64 in² in 2 amps, and I can do parts from 10 in² to 405 in² with no trouble at all.