Polishing to a mirror shine - problem!

Hi all,

I keep getting a recurring problem when trying to polish silver ring shanks to a mirror shine. I am polishing by hand from 400, 600, 800, 1200 and then final polish with luxi blue and white using my Foredom.

However, I keep getting a stripe down the middle of my ring shank where it looks like the sand paper/emery stick has not touched.

I have tried polishing with the curve of the ring with a stick, and free holding sandpaper. I have tried going across the ring, I have tried doing a slant diagonally across!

Every time I do it it looks like I have caught all of the silver with the sandpaper at each grade but when I go to polish if up - still have the stripe down the middle.

The rest also looks unfinished too - so maybe I need to use further grades of sandpaper for a mirror shine?? But I am at a loss with my stripe!!

My current ring has had 3 polishes and still does not look anywhere near mirror. I am a little scared to keep at it though as feel nervous about how much sanding you can do!

Any ideas of what I am doing wrong???

If it is a darkish blue-grey stripe it is firescale. This is copper oxide and occurs fairly deep below the surface. The cause is too much concentrated heating with an oxidising flame (one with a sharp blue cone)

The curse of firescale if you care about it, is that it becomes more visible the shinier you make the surface. So you can either settle for a matte finish, or keep filing, grinding and polishing until it has gone.

These Scotchbrite polishers from Cooksons also work well for this, without being too destructive.

http://www.cooksongold.com/Jewellery...prcode-999-ACR. Dennis.

Arrr ok, thanks Dennis - I might have one of those in my pack of polishing bits I got with my dremmel or foredom.
Will try this and see how it goes.

Could you post a picture of your stripe so we have an idea before you attack it with anything else? Is it in the same place on every ring?

I started out sanding by hand and could never get a finish I was happy with no matter how hard I tried or how many instructions I read.
I now use the Everflex rubber burrs on my pendant motor and haven't had any problems- unless it is fire scale when I found Dennis tip about the Scotchbrite to be a great one - I used that then back to the red then green Everflex.
http://www.cooksongold.com/Jewellery...prcode-970-360

Thanks all - yes it is Caroline - same place - down the centre like another band! I looks like I haven't 'hit it' with the sandpaper but I have sanded every which way to try! I might try machine instead of hand - thanks for the suggestions.

Can post photo later but at my day job today. Thanks for the help.

If it is Firescale - you are better to make sure it doesn't happen in the first place, rather than try to polish it off.

So, if you coat the item your are heating in flux (all over the piece rather than just where you are soldering) , this causes a barrier to form, and you will not get firescale. The other option is to put in pickle (acid) to remove the copper, rather than trying to polish it off.

Hope that helps ....

Fire scale only down the centre seems strange, are you using binding wire to solder them?

Hi Paul,

I have pickled it - in Picklean warmed in a slow cooker. Left it in there for 40 mins or so. Thanks though for the help and advice - all greatly received. Will try the flux idea.

Caroline - No - no binding wire.

One reflection - I don't think it's fire scale it looks like scratches - like the sandpaper has not hit it but as I said - sanded three times and every which way I can with different grade?!

Sorry to keep on asking obvious questions but are you wrapping your sandpaper round your file so that it's sanding evenly?

I seem to remember an earlier post where someone was complaining about a line that wouldn't disappear on their silver but that wouldn't explain why this was down the middle of each ring :/

Caroline - no obvious it good!! I have tried both - I used emery sticks and tried sanding just with sandpaper on its own - thought my emery sticks might be 'too wide' and that's why they were not hitting the middle ridge so tried it free hand too to make sure I hit all parts - still no joy.

Does the offending patch look anything like this?:
http://www.cooksongold.com/forum/att...3&d=1396904353

Yes! So, I thought it was fire scale - I pickled it and then sanded twice again - all grits, emery and free hand and finished with luxi. Now it looks like that but more silver! What was the problem with this one? Thanks

Quote:

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Originally Posted by silver70

Caroline - no obvious it good!! I have tried both - I used emery sticks and tried sanding just with sandpaper on its own - thought my emery sticks might be 'too wide' and that's why they were not hitting the middle ridge so tried it free hand too to make sure I hit all parts - still no joy.

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If you sand free hand it'll shape into your fingers, I would say from the photo there is a bit of a bevel in the silver. I would take a flat file with the emery wrapped around, this is much more rigid than even emery sticks and sand in a curved motion constantly turning the ring, you might have to go round a few times until you get a flat surface. It would be much easier to show you than explain :)

I agree. I've noticed that when some flat section is bent into a ring it has a tendency to 'cup' so that the edges are higher than the middle.
I have to file circumferentially around the ring until I see the file marks down to the middle.
The effect is accentuated if you have worked it on a tapered mandrel.
As I say, I file, then buff.

I would agree with the file too if it's really deep, there is nothing more useful than some really good hand files of different grades. The finest would probably take it down to just needing fine emery then a polish. Filing an arc be it rings or bangles is all the wrist action and just needs practice. Think we've all solved it now!

Many thanks - I will wrap my grades of sand papers around my files and give it another bout then! Not sure I really understand the 'science' behind the edges being higher....I will have a look at the ring when I get back to my bench but thanks! It seems that this is what is happening! :) :)

If I file, I am worried I will take too much off so I will sick with sand paper for now. Do I need to go for the edges more than the middle at first them or still go all around still?

Am I to still work up the curve of the ring - is this what is meant by curved motion? Just worried about getting a flat point or not sanding with the curve of the ring and spoiling it,

Keep the file flat as possible so you'll take the high points down to the lowest equally and yes work round the curve , not across the ring moving the ring on as you work round and you won't get a flat point

Thanks! I will have a go!

Just as a note - next time I bend a flat piece of sheet into a ring - is there anyway of avoiding the cupping? I use a tapered ring mandrel.

Well, I have made lots of rings over a long period and never heard of this problem. But then I have never taken files and buff sticks to the surfaces either.

In another post today, I wrote this:

Using your motor with as light a touch as possible and not staying still in one place, I would start with these:

http://www.cooksongold.com/Jewellery...prcode-999-ACR

and finish with these: http://www.cooksongold.com/category_...y=Radial+disks going through all the colours starting with yellow.

By the time you reach green, a final shine if necessary, could be effected by a polishing cloth.

You might try this method in your case too. Dennis.

Thanks Dennis - the links do not work presently (think the site is being worked on) but I realise what the radial disks are - must invest in these!

On a future note - is there any way of preventing the cupping?

If I understand you correctly, the tapering of the ring can be rectified if you turn the ring around and hammer it on the other edge.

Yes, but on a micro (macro?) level, it will always be >< shaped, it has to be if you are using a taper to form it.
you end up with two opposing very very slight tapers, the outside edges (leading edges) are a very slightly larger diameter than the centre diameter. The wider the ring, the more pronounced effect.
I think it is this micro, virtually unnoticeable dip which is causing the problem. I could easily be wrong though.
A few curving wipes with a fine file around the circumference takes the outside diameter down to the smaller centre measurement.

The ring should never be shaped if you do as Carole says and on every full working of the ring you take it off the mandrel and turn it round and put it back on and work that side. As long as you keep on turning the ring round it should be flat. Once finished on the mandrel you just go round the ring with your hand file wrapped in emery paper to take down any possible unevenness

Just an update: got back to sorting the ring today. Went round it with my file and the a mixture of hand and Foredom polishing and it has come up a treat. Have now invested in some radial discs too.

Thanks for the other advice too - I did turn it but probably not a regularly as I should! :)

Many thanks - many lessons learnt!

Really glad it all worked out :)

Yes - thank you all who helped :)