Tumbling help!

[anturdesigns]

Hoping someone might be able to help me out with what I'm doing wrong please!

Have got myself a mini tumbler to save on polishing time, but my pieces are not coming out nice and shiny like I was expecting. I thought maybe it was the pins, so I painstakingly removed them all, but it made no difference.

Hopefully you can see the attachment. I'm using "PMC 960", and pieces made from the same stuff polished up beautifully when my tutor tumbled them! The shot is stainless steel of lots of different shapes, tumbled with barrelbrite.

I'd be grateful for any advice!

[Dennis]

Tumbling only burnishes, so if your piece has a texture when it goes in, it will have a texture when it comes out--but shiny. Dennis.

[anturdesigns]

Thanks Dennis.
Only, it didn't have a texture going in! It was lovely and smooth (I did most of the hard work before putting it in, it just needed the shiny finishing touch)! It did it to another piece as well (Alkemé this time, done separately). :(

[ajda]

Did you tumble a number of pieces together? I've pretty much cured any problem I had with pitting/dimpling by removing all the pins (as you did) from mixed shot. But I've made the mistake of tumbling a batch of pieces that included some with sharp edges/corners which gave me the same dimpling as the pins did. Is PMC960 appreciably softer than the sterling version? I understand it's a blend of fine and sterling clays.
Alan

[anturdesigns]

Yes, that's right Alan (on both fronts) re the 960. And I think you might be right on the pitting thing as well! Some of the pieces have sharp edges potentially. Going to try again with those pieces out (once I've re-sanded it!). Am I best just sticking to balls do you think?? What about these shapes... (See pic - hope it worked)

8425

[ajda]

It's difficult to tell if those shapes ("dish cones"?) are OK or not without doing a bit of trial and error, which you'd probably prefer to avoid... I have some similar "ball cone" shapes, mostly smooth and rounded all over, but with a small pin-like protuberance on one side similar to those in your photo - even though they don't look sharp, I suspect they may contribute to minor dimpling. If in doubt, I would just use the balls. Given the softness of PMC960 you might need to err on the side of caution. I use Argentium 960, the same silver content as yours but significantly harder even than sterling (at least, once it's been fully age-hardened by heating), and I still have to be very cautious. Have you checked what your tutor uses?
Alan

[Dennis]

The point of mixed shot, is that it will find and enter all the grooves, angles and crevices. Once you start selecting shapes to remove, you begin to get shading, because an area remains untreated.

I have patiently ground and polished my shot by hand and run it for hours with pebbles. Its performance has improved, but still there is minor pitting. I have also tried shot from three other sources, with no improvement.

Some members have changed to magnetic polishers, with improved results, although, strangely they have only fine needles. The better magnetic polishers are expensive and there is still a learning curve. An entry level model is the Bumblebee. Dennis.

[ajda]

Interesting points (no pun), Dennis. Do you think there's a difference in the way the magnetic polisher moves the pins and the pieces being polished, so that they perhaps rub together more and strike each other less - or with less violence - if you see what I mean?

[joella]

Hi,
I've had this sort of marking on my pieces too, but I don't any more. I'm not sure which of the following things made the difference, as I did them all before putting anything in it again:

Ran it with just the shot and water and barrelbrite for about 2 days
put a lot less water in than I had been doing
was a bit more generous with the amount of barrelbrite to water than I had been

Hope this might be useful

Sue

[Dennis]

In reply to your comments, Alan I don't know but I'm hoping Lauren will join in as I believe she uses one. Dennis.

[jayneharrison]

After similar problems, I have had better luck with my home tumbler by replacing the mixed shot with tiny, 2mm ball bearing style shot. Small enough to get in the nooks and crannies but no noticeable pitting.

[anturdesigns]

Thanks everyone.

I have emailed my tutor but she hasn't replied, so thought I would gather some wisdom here, and you haven't let me down!

Have ended up doing my current pieces by hand, just don't want to risk it. I will definitely be trying the suggestions here - smoothing the shot sounds like a good place to start, then test it on something cheap! A significant portion of the shot certainly has a rough feel. I'm afraid I can't afford a magnetic polisher (yet!), maybe one day!

Thanks again all!

Hester

[metalsmith]

My tumbling results have always been a little too matt for my liking. Then I bought a new tumbler and it came with some shot that was smaller than my existing - and the results were transformed.