Electrolytic Capacitor Question

[mart.s]

Why is it that electrolytic capacitors get heavier (in weight) when they are old, As I understood it -the electrolyte evaporates after time and use, so wouldn't this make them lighter.
Over the past few weeks I have been replacing lots of large old caps in psu's and amps and have discovered the new ones (identical in size, value, voltage, and manufacturer are actually lighter than the old ones by 4-5 grams.

Anyone have any ideas on this?

[DF96]

You are sure that the manufacturer is using precisely the same process and materials? If caps are old enough to need replacing then something is likely to have changed over the years. If the caps are failing after only a short time then one would hope that something has changed to prevent this in the future!

[Mooly]

Identical in size and value maybe. Todays caps are made with newer technology and materials and techniques.

For a moment I though you were meaning the same cap got heavier as it aged.

[Elvee]

Originally Posted by mart.s

Why is it that electrolytic capacitors get heavier (in weight) when they are old, As I understood it -the electrolyte evaporates after time and use, so wouldn't this make them lighter.
...

Anyone have any ideas on this?

Nothing to do with evaporation, quite the opposite in fact: older technologies used essentially water based electrolytes, which had a density >1 because of dissolved electrolytes, whereas modern high temp caps use much lighter organic solvents. Which doesn't mean they are better (except for temperature, of course): when you compare 40y old Siemens caps to modern ones, there is little to chose from, except if size and an operating temp of 115°C is of paramount importance, of course...

[AndrewT]

less aluminium?
the etching of the aluminium surface MUST reduce the average thickness and thus the weight.