Luis,
Even you must agree that (considering highlights are more sensitive to
fogging than unexposed areas) if the unexposed area fogs, then it is
most likely that the highlight areas will be foged as well. I have not
studied the cumulative effects of fogging, but will gladly accept your
findings.
You also mentioned:
> Fogged highlights where the fog is not caused by a poor safelight is fairly
> common. The main cause, as explained in a wellknown book, is a ferric
> oxalate that is too old.
>
If what is meant is that the ferric oxalate is or has gone "bad", this
is true. However if the ferric oxalate is "good", then this test will
certainly be useful in the determination of the effectiveness of one's
clearing process.
Jeff