"Chuck Harris" wrote in message
...
Hi Alan,

Because of the physical construction of an electrolytic cap, it MUST
change capacitance if the oxide grows thinner in storage, or thickens
thru reforming...

But, I too notice that sometimes the change is large, and othertimes
it
is not.

I suspect that what is happening is the oxide layer thins out only in
spots (probably around impurities) in some caps. These spots are
large
enough to readily affect the leakage current, but are small with
respect
to the total surface area of the plates. Because they are a small
percentage of the total surface area, they only minimally affect
the total capacitance.

-Chuck Harris


That makes sense. It would be interesting to know how many amp-seconds
per square foot is needed to form the initial oxide layer vs. how many
are needed to reform a cap. Generally, the reforms run a few mils for
less than an hour. A few minutes is typical.

Frank Dresser