Hello Sameer,
I experience the same issue as well. These greyish/brownish discolourations
come from (slightly) unbalanced rotors scratching against the brown plates
of the housing. If the scratches are more in the middle the marks originate
from touching the coil. On the other hand, if I want to test for spinning
trouble I draw one or two lines with a sharpie along the length of the
rotor. If those markings are disturbed/scratched, you know the rotor has
touched the housing or coil.
I don't try to clean the scratches off, but if there is an easy way, that
might be an attractive thing to try.
Happy resonating and Holidays,
Ulli
On Thu, Dec 14, 2023 at 5:36 PM Sameer Al-Abdul-Wahid via groups.io wrote:
> Dear AMMRL,
>
> Over the years, many of our 4 mm MAS rotors have developed a
> greyish/brownish discolouration on the outside. It’s usually limited to the
> top and bottom sections of the rotor, and it won’t come off with water,
> isopropanol, or acetone.
>
> Does anyone know what this is and how to best clean it off? We want to
> clean the rotors so we can determine if this is an ongoing issue or due a
> previous probehead. My first thought is to try a solution of Bar Keeper’s
> Friend (or diluted oxalic acid), but could it affect the rotor in some way?
>
> Thanks,
>
> Sameer
>
> --
>
> *Sameer Al-Abdul-Wahid*, Ph.D. *|* Manager
> Nuclear Magnetic Resonance Centre *|* University of Guelph
> 519-824-4120 Ext. 58914 *|* s.wahid_at_uoguelph.ca
> http://nmr.uoguelph.ca/
>
>
--
Dr. Ulrike Werner-Zwanziger
Adjunct Professor
Department of Chemistry, NMR-3,
Dalhousie University
6274 Coburg Road
PO BOX 15000
Halifax, NS B3H 4R2
e-mail: Ulli.Zwanziger_at_Dal.ca
Tel. 1 902 494 8085
FAX: 1 902 494 1310
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Received on Thu Dec 14 2023 - 18:35:43 MST