[Harp-L] Re: Crystal mic element in a vacuum (was which mic to buy)

[BluzeHarp@xxxxxxx]

In a message dated 2/25/2011 11:10:20 A.M. Mountain Standard  Time, Vern 
writes:
I don't know much about crystal mics but from the posts about them  they 
seem to be some kind of hygroscopic salt.   Would subjecting a  degraded 
crystal to a vacuum restore its "zorch?" ...
 
Vern, I've tried that (38 year refrigeration background).   I've been able 
to moderately improve output  on a couple weak elements, most weak ones 
didn't  improve at all.  Full 'zorch' was never restored.  One  weak specimin 
died!  I'd say less than 10% of the  weakened elements are candidates, but, my 
sample size was much too  small to draw any definite conclusions.  Zero 
dead elements  came back to life.
 
FYI... 'zorch' properly applies only to magnetic and  ribbon type elements. 
 The correct term to apply to a crystal  is 'zooch'.  Believed to have been 
first  uttered by Little Walter, after gunning down some drunk  who slopped 
a beer into his mic at a bar gig...
 
I used a 5 CFM two stage vacuum pump &  an electronic vacuum gauge that 
reads in microns.  3 hours in  deep vacuum & tested with no noticeable effect, 
likely because  it takes longer than that to boil the moisture out of the  
salt. Then 72 hours & tested.  Pump has to keep  running, can't just pull the 
vacuum & close off the chamber.  Vacuum  was released very slowly in order 
to avoid concussive effects  on the fragile elements.   
 
These elements can fail in different ways, moisture  contamination being 
but one.  Too much moisture & the salt will  just dissolve... no comin' back 
from that.  I think some of the weak  output ones may be partially fractured 
rather than  wet.  Removing moisture from a fractured AND wet crystal could  
cause it to shrink & pull apart, might be why the one I mentioned  above 
died.
 
Or were you referring to the Hoover you keep in the hall closet?
 
Christopher Richards
Twin Tone Harmonica Microphones
www. harmonicaplanet.com