[ARC5] Crystals in WWII

[Dennis Monticelli]

Ken,

Thanks for your comments.

I have learned through much experience that if you take a typical FT-243 or
CR-1/A WW2 era crystal that is kind of sluggish and give it a brief dip in
a weak HF bath (less than 1 min) at room temp and then follow that with a 3
step rinsing process involving both DI water and alcohol, the freq will
jump up nearly a KHz and the activity comes back.  All that "loading" on
the surface has been removed.  If you return the blank to the weak HF bath
for further etching it will experience a very slow increase in freq
proportional to the minutes in the solution because by this time the acid
is working on a native tightly-bonded crystal surface.  I did a time graph
once and found that most of the cleaning took place in the first 15 sec.

Dennis AE6C

On Fri, Mar 15, 2013 at 1:07 AM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 15 Mar 2013 at 0:40, Dennis Monticelli wrote:
>
> > I think the "dirt" problem had mostly to do with fine grit left over
> > from the grinding process and also quartz molecules left weakly
> > attached to the crystal.
>
> Yes. Exactly.
>
> >  Neither would appear to the eye after a
> > routine wash.
>
> I know that when grinding crystals to frequency by hand, a good method of
> cleaning them is with a toothbrush and plenty of scrubbing. But, even doing
> that will not get the crystals completely clean.
>
> To REALLY get them clean requires etching with HF.
>
> >  The fix was discovered and implemented by Bliley.  They
> > were doing an acid etch to take a ground blank a short distance to the
> > final freq.  It turned out that the etch also did an outstanding job
> > of removing several atomic layers (where the surface damage was) and
> > leaving behind a clean nicely ordered crystal lattice.
>
> Yup.
>
> >  There was
> > nothing left on the surface to redistribute after manufacture and use,
> > hence no "aging."   Bliley didn't want to share the knowledge because
> > they wanted to retain an advantage in the market after the war.  The
> > govt twisted their arm and the technique was shared, just as all the
> > previous crystal technology had been shared earlier in the war to
> > create the cottage industry.
>
> Yes, but if the gummint hadn't twisted some arms then and there, many lives
> would have been lost.
>
> BTW, for those who are interested, a product named "Whink", available in
> most supermarkets in the laundry supplies section contains a small amount
> of HF.
>
> It will etch crystals, although very slowly. It does an excellent job of
> cleaning
> crystals after grinding them by hand.
>
> Ken W7EKB
>