Thursday, April 10, 2014

Do you Mass Finish?

There are many 'helpers' to the busy metalsmith, a big one being the 'mass finisher'. If you're not familiar with the process of 'finishing', it can be a real chore and a real skill to be able to finish a piece of silver jewelry.... to achieve a good polish can take a lot of hand power- filing, sanding, polishing. And the way you go about this varies dependent on the metalsmith. 

I have always struggled with finishing/polishing because a) I'm so happy something is almost done that I'm lax to put the time in to finish it 'right', and b) I haven't had a good education in the art of finishing.

And, yes, it is an art!

So here comes mass finishing to the rescue!!!! Above you can see 2 tumblers. The one on the right is an antique Lortone tumbler, believe it or not, used by me and my Dad 35 years ago (when it was new) to tumble rocks to shininess- only took 4 weeks to achieve! We'd change the grit every week and this powerhorse would be constantly running for a month!

I don't use it anymore because the plastic liners on the spinning rods had long since worn off. You can see rubber debris in the bottom where I had put rubber bands around the barrel so they would have enough friction to move on the spinning rods, and everytime ultimately they got worn down to crumbs. 

So, I bought myself a replacement from Harbor Freight that actually fits 2 barrels- on the left. The idea is that you put the pieces to be polished in the barrel, and it spins on the spinning rods, in the process rubbing against some sort of media, thereby polishing by burnishing the metal surfaces.

There's a new type of tumbler that's called a vibratory tumbler- it essentially vibrates or shakes the contents, which results in the same outcome as these traditional rotary tumblers. They are also sold in many sizes- for bigger or smaller jobs. Something I'd like to upgrade to!

This media is an abrasive pyramid-shaped material that actually slightly scratches or grinds the surface of the metal ever-so-much. It is helpful to start with this media first, I've found because it lays an even foundation to the metal and produces a better surface in the end. There are rougher media available, too, but I like just a subtle, almost sand-blasted look that this type provides. There are many other types of media (even walnut shells!) that produce a variety of finishes, depending on what the metalsmith wants to achieve.

As the barrel spins with the metal and this media inside, as well as water and a dash of dish soap to make everything lubricated and hence rub together nicely, the media essentially 'scratches' the metal evenly. I let them tumble for an hour or two.

Then, out they come, all scratched up and ready to go into a final polish. The above media is a polished porcelain. There is also stainless steel 'shot', which is essentially doing the same thing- polishing, but I feel I get a better finish with this stuff... the various sizes and shapes are for getting into small spaces. The stainless steel mixed shape shot left a bit of an orange peel texture on my pieces. This porcelain stuff leaves a smoother finish, but requires several hours in the tumbler.

That's okay- it's 'working' while I do other tasks!

Here're a few pieces after coming out of the abrasive media... all of the essential shaping, filing, and sanding has been done beforehand. You can see they look sand-blasted, with a matte-white finish.

Here they are out of the polisher- definitely shinier! It is still impossible to get into all the little areas of granulated pieces such as these, but since I am going to have them oxidized and then re-polished, the parts the media can't reach will be dark anyway. But these are ready to go to the caster to be replicated as rings, pendants and earrings! Then they will be mass-finished again, and findings and stones will be added.

I am glad mass finishing exists- it's like my little helper!

Of course, there are lots of ways to polish and finish by hand, but that's a subject of another post! Here's an overview of finishing techniques:

Can't wait to see how these come back from the caster- check back here in 3-4 weeks!!