Keith G wrote

From what little Physics I do remember, I thought it was quite the
opposite of "At very cold temperatures (below -312°F), the molecules
will align in a more uniform, compact structure through the removal of
kinetic energy." - I thought the only way molecules could move in solid
objects was if you *heated* them up! (Which is why blacksmiths ring the
anvil when bashing red-hot metal about - to 'jiggle' the molecules!)

In essence, you are correct and the quote is either incorrect or
misleading. :-)

If you wish materials to 'crystallise' then in general you may find it
useful to cool them slowly *through the range around their melting or
softening point*.


Yes, I'd call that 'annealing'....


I'd suspect that the materials used for the electrodes in
'valves' would be well below this at normal room temperature. Hence it
isn't clear cooling them to very low temperatures will do what is claimed.


Exactly!!


Hard to see that if will affect the 'structure' of the vacuum, either...
:-)

Hence IIUC you'd have to first heat the valve to the point where the
materials were starting to melt, then slowly cool it *if* you wanted any
serious recrystallisation. But simply using it and then allowing it to cool
to room temperature would probably do much the same.


You could always heat them up and hold them at an angle of 71 deg pointing
North and then hit them smartly wiv a hammer - it would make them very
slightly 'magnetic'....

Worked with Miller and some Lucas dynamos, sometimes, reputedly :-)

It must take a while for the heat to escape. How do they know when it's done?

How do they avoid cracking the glass or the metal, or weakening the joints
between dissimilar materials?

There seems to be common in the claims something about relieving "internal
stresses", whatever that means. It may be plausible...I forget if I ever knew
anything about metal at low temperatures...presumably crystals can be unformed
by making them either very big or very small.

Perhaps it is the equivalent of work hardening, where discontinuities are
squeezed out of crystal boundaries?

Perhaps that then effects the way that perveance-enhancing constituents of the
cathode alloy migrate to the surface?

cheers, Ian