Re: ATM forwarded message about dog biscuit

[Scott Rychnovsky <srychnov@chem.ps.uci.edu>]

>Hi Buck,
>
>
>> > Why is a rough surface called dog biscuit?
>> >
>> > How do I know if I have it?  What does it look like in the tester?
>
>It's quite similar in appearence to a real dog biscuit when observed
>in the Foucault, without the Ronchi bands. A smooth mirror means no
>anomalies of any kind, aside from the paraboliodal shadows, of course.
>


I have never observed a dog bisuit with a Foucault tester, but then I have
cats.

I find that my measurements on a smooth surfce are more consistent and I
only observe a clean, uniform shading.  With a rough surface I can see
lighter and darker patches that make the Foucualt reading less reproducible.


--
Scott Rychnovsky
srychnov@chem.ps.uci.edu