When I started tumbling my work, a while back I bought some mixed shot from Sutton Tools, as that seemed the best buy at the time. I saw at once that the needles were rather jagged and sure enough the finish was disappointing and full of tiny pinpricks.
So started my quest, if not for the grail, then at least for a way of dealing with this problem. First I sorted out the needles and set half aside. The rest I ground and polished one by one, before putting them back. Then I tumbled the shot with pebbles for hours. The improvement was not overwhelming, but as the pinprick texture was only evident on smooth surfaces, I settled for re-treating those with Micro-Mesh at the end.
The great benefit of tumbling is that it burnishes textures, without removing metal, and reaches into those recesses, which are resistant to other methods of cleaning.
This experience has been a cause of complaint by other members since and as some smoother shot was recommended recently* from Rio Grande, I sent for some to compare.
The test pieces of copper in my picture below, were cut from the same sheet. They were slightly tarnished and had some light striations, presumably from rolling at the factory.
As a precaution the new shot was tumbled with soap for some hours first. Then the test pieces were each tumbled for about three hours, one with my old shot and one with the new. The weight of shot was approximately the same.
You can see from my picture that the results were very similar. Possibly the horizontal striations are more visible in the Rio Grande sample.
Conclusion: The old shot had been painstakingly modified and conditioned by use over perhaps two years. The new shot from Rio Grande produced similar results at once. The pinprick texture, although now feint, persists. The search goes on. Dennis.
*suggested by mizgeorge, who sorts the wheat from the chaff for us.
http://www.riogrande.com/Search/339097%20media. Total price about £22.00, when imported.
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