I found the following references on a related web-site regarding the figuring of the time:
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Figure out how long to anodize the part using the following rule - 900 amps per minute per square foot of part or 15 amps per square foot of part per hour.
The focuser tube has 42.4 sq " of surface and is drawing 2 amps according to the meter on the power supply. 900/2 =450 amp min, and 42.4/144 = .294 sq'. So 450 times .294 = 132.3 minutes in the tank.
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I was trying to generalize this statement, and I found flaws, such the units on the value of 900 would have to be A*min/sqft to make the math work as follows: 900(A*min/sqft)/2(A)=450(min/sqft)*0.294(sqft)=132.3(min).
When I applied these equations to my part, I found that I was drawing 1.01A and when I incorporated the part size into the equation, it resulted in 120min. The part bubbled for about 110 mins then stopped. I waited for the full 120min, removed and cold-washed the part, and it looked great.
I saw the 90 min in the manual, but it appeard to me as though it was only appropriate for the part being discussed, I did not realize this was a generalized value no matter the part. Perhaps that could be made clearer in the manual. My PS has a volt-meter and an amp-meter. The amp-meter doesn't appear to work properly, so I in-lined my digital meter and got the 1.01 A rate. Over the entire session, the voltage held steady at 7.5V and between 0.99 and 1.01 amps. The reading never changed, untill I removed the part after 120 mins.
Not sure exactly what I did wrong, but the part came out great anyhow. Ill keep experimenting.
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