Do you, and if so, what do you use?
I've only tried a couple of batches and had mixed results. One batch was tumbled with stainless steel shot for 4 hours before the colour started to fade. Rings from another supplier couldn't be tumbled for 5 minutes before the colour went.
I took delivery of some crushed walnut shell and crushed corn (impregnated with polish) this afternoon. I'm on the second hour with the walnut with no fade. A couple of questions spring to mind:
Do I need to put anything in with the walnut?
Do you think the polish on the corn will strip the colour?
This is all with a rotary tumbler by the way.
Thanks, Greg :) Sounds like my first lot.
Do you mind me asking where you bought the rings.......or did you make them?
Lesley, it's not so much that the color is fading as you are wearing off some of the oxide layer made by the anodizing. The higher the voltage, the 'thicker' the oxide layer, so the color is wearing off but dropping to a lower voltage color. Anodized Niobium and Titanium DO NOT FADE.
From here on, I've asked my husband Rick to do the 'tech speak' as he really knows what this is all about!
"Anything done that affects the depth of the oxide layer WILL affect the color. How much it is affected depends upon the particular “Lot” of metal and its surface preparation. Tumbling in steel shot will burnish the oxide layer. Tumbling in anything abrasive will ‘wear’ the oxide layer. The degree of “wear’ will dictate whether there is a color shift or whether the base metal is being exposed. The surface preparation of the particular batch of niobium from the commercial wire source will also affect the speed of color change. Realize that all these oxide thicknesses and other surface dimensions are measured in 0.5 to 1 Millionth of a Centimeter in thickness. It is not the oxide that you are seeing. It is the oxide’s effect upon light that you are seeing.
That leads to the question of “What is the reason for wanting to tumble Niobium or Titanium?” ANY tumbling is GUARANTEED to have an effect upon the oxide layer, even if only minutely. If a person really wants to tumble a reactive metal that has been anodized, the media and time should be balanced to cause the least amount of damage to the oxide layer.
If the reason for tumbling is to “Clean” a piece, then the better alternative is a relatively non-abrasive process. We ran a test a few months ago when we started carrying niobium and I wove several strips in a high voltage color and we ran them through the dishwasher, the last piece went through hundreds of washes before showing any significant colour shift. This being said, water quality could have an effect on the oxide layer. Anything that will add a film to the oxide layer will affect the way it causes the colors. I would wonder about the walnut, because of its abrasive nature and if your medium is impregnated with polish that is also abrasive (and most polishes are) then you could see some wear. Polish also contains waxes which will build up within the oxide layer. Rubbing alcohol is a good solvent to use for removing body oil and other waxy substances.
I polish my niobium in a rotary tumbler for very short durations for cleaning purposes only - my pieces also are mostly mixed with Argentium - and I've not seen any significant wear, but I don't have to polish them often either.
If the "Reason" for tumbling is to work-harden the piece, you can stop wasting your time. Niobium is VERY SLOW to work harden. You can tumble niobium until the entire oxide layer is removed and it will not be much harder than when you started, unlike sterling which is relatively quick to work harden. If you're tumbling to work harden mixed-metal pieces, I would start with 15 minute intervals instead of times measured in hours. Varying the amount of liquid will also affect the time. As with many things, it can be a delicate balancing act to fine-tune the process."
I hope this helps you to understand what anodizing really is and how to treat the anodized material - it has a certain fragility and must be treated with care... it's not 'just' a pretty, colored metal ring.
Lesley, there are no 'dumb plum' (love that!) questions, but Rick and I have agonized over niobium for so long that we feel we've really run the gamut and come up on the other side with a decent understanding of the 'beast'. Not only will the range of colors change, but 70 volts today (color-wise) may not be the same tomorrow. We've come to understand that there will almost always be some 'orphans' in every batch and some days that 70 volts may be the prettiest range of 5, 6 or even 7 colors. And the inconsistency in the wire itself is the biggest problem. There is a more consistent grade of niobium available than what we use, but it would cost more than double what our niobium presently costs, and frankly, we don't think anyone would pay what we would have to charge.
Tumbling to remove burrs is probably not going to make much difference - our finishing process requires days with a very coarse medium to remove the majority of the burrs. We only use stainless shot to polish once the major de-burring is done. Each batch will react differently - depending on the amount of polish on the ring... uuuummmmm - how can I put this? Though the ring feels smooth, the surface is actually peaks and valleys and the light reflects back at different angles - more peaks, more consistent color - less peaks, more polish and shimmer and the color changes from the angle at which you view the ring, the angle of the light and possibly any color reflected from the surroundings. Our rings are highly polished and we get a shimmer that other suppliers don't, but it takes days instead of hours to get rings that smooth. When we anodize we try to use natural light, as incandescent lighting is yellow and completely changes the color of the rings. Better cloudy, grey natural light than yellow light - you should see us on a rainy day, huddling by the window checking for the proper color... it's quite a process! We've gone through pounds and pounds of niobium working on better cuts, polish and color.
Cat's Custard! (love that one too!) No dishwasher! There's no way I'd give mine up and there's just 2 of us as well... so the next best thing is a screw-top jar filled with equal amounts water and rubbing alcohol and the tiniest amount of dishwashing soap - a drop might be too much, so just run your finger across the spout and stir the mixture with that finger. Too much soap might leave a residue, so less is definitely more. Add your niobium and shake for a couple of minutes to cut any body oil or other 'stuff' you want to remove. Rinse and dry... that should do it!
Sorry to get so long-winded (actually, a little proud of myself - I could field this one all on my own! LOL)
A little off topic, but maybe you can clear this up for me.
Days of tumbling to remove burs? It sounds to me that your cutting method may need to be refined. I have cut the gambit of materials from
aluminum to karat golds with nearly every material in between including
exotics and the best way to remove burs is not to have them in the
first place. I do have a batch here and there when my saw is showing
wear, but I rarely have to tumble any materials besides stainless (and other really hard metals like inconel) for
more than 4-6 hours. Usually any metal that comes out after 4 hours has
a blinding shine niobium included, no burs in sight because they were not there to begin with. For reference my media "supply" includes ceramic, porcelain, plastic cones, stainless shot, rice, walnut, corncob, flour, and blasting sand. I just use the one that works best for each material and whether I want to burnish or polish.
I understand that your surface preparation before anodizing takes a while, but days just to remove burs seems excessive unless you have really bad burs.
Tumbling to remove burrs is probably not going to make much difference - our finishing process requires days with a very coarse medium to remove the majority of the burrs.
It never fails - you put yourself out to help someone understand a process and someone feels the need to pick out one small part and make a mountain out of a molehill. Maybe I overstepped in my phrase 'requires days' - I do not work with the wire at all and I usually know when Rick cuts rings and it is several days until I get them for sorting. And at one time, it was several days to get the rings smooth - I guess we have improved since then. Does it really matter to you? I think it shouldn't - it works for us and since Rick is a retired engineer I can guarantee that our saw and tumblers and other equipment works as well, if not better than most anyone else's. But I'll let him have his say...