Grey blemish on sterling silver pendants

[handmadeblanks]

Hi,

I made a few pendants and for the first time I used my pendant motor to pre-polish using Yellow Luxi before putting them in the tumbler with stainless steel shot for the final polish. When I polished the pendants they had a near mirror surface, absolutely beautiful. I scrubbed them with a soft toothbrush and dishwashing liquid before tumbling. After tumbling they still had a very shiny finish. This was yesterday. I checked them today and some of the pendants have developed a kind of grey blemish in areas and I can't figure out what it could be. I don't think I missed it yesterday. The strange thing is, it's only noticeable when you hold the pendant at certain angles.

It can't be fire stain can it? I thought it would show up at the pre-polish stage.

Any ideas as to what it could be?

I appreciate any help/advice you can give. Thanks in advance.

[ps_bond]

It sounds like it could be - FWIW I check for firestain by holding a piece of tracing paper over the metal; it kills the reflection so you can see the colour more clearly. Equally, any polish residue looks much like firestain too.

Very annoying when it doesn't show up until final polish though.

[Dennis]

Actually the higher the polish the more it shows.
Daylight enhances it too.
Bring it back to a satin finish say with a glass brush and it will disappear, unless it is very severe. Dennis.

[CJ57]

Photographing it in a light box is usually when I see the specks I've missed and they come out again for another polish. The light on my polished sometimes shows it up otherwise as younsay it'll catch you in daylight

[Dennis]

Here's my Modern London brooch. City Hall had an ugly patch of firescale. A quick brush with a fibreglass pencil gave it a contrasting satin finish. Firescale gone.

Hot Tip: Start using Argentium silver. It doesn't get firescale. No copper. Don't be a slave to your polishing motor. Watch tele instead. Dennis.

[china]

Coat your Stirling with Boric acid flux before soldering this will help prevent fire scale

[handmadeblanks]

Thanks everyone for your input. I really appreciate your help!

@ps_bond, I was hoping someone would say polishing residue but the overwhelming consensus is firescale :'(

@Dennis, I thought with Argentium silver only some of the copper is replaced with germanium, not all of it.


In regard to firescale:

I didn't do any soldering at all on any of the pendants. The only time I used a torch on the silver was for annealing as I rolled the ingot down to sheet. I followed as close as possible the correct procedure in regard to having the room dark and keeping the silver a dull red colour for approx. 30 seconds.

I was/am under the (possibly mistaken) impression that annealing temperatures aren't hot enough to cause firescale.

I am obviously wrong.

[Dennis]

Dennis, I thought with Argentium silver only some of the copper is replaced with germanium, not all of it.


Yes You are right. Only some copper is replaced, but you definitely don't get firescale.

As for annealing, that is a good time to have a bottle of liquid flux and a brush handy for prevention. Dennis

[handmadeblanks]

Yes You are right. Only some copper is replaced, but you definitely don't get firescale.

As for annealing, that is a good time to have a bottle of liquid flux and a brush handy for prevention. Dennis

Hi Dennis,

Would the boric acid solution work just as well if it is diluted with water or does it need to be methylated spirit? if it's methylated sprit does it matter if it's dyed? I can't seem to find clear.

Thanks.


On a side note: I managed to rescue my pendants by sanding from 180 - 1200 and then polishing again with luxi yellow and luxi red. Phew!

[china]

Needs to be metho after coating item you light it so the alcohol burns off and you are left with a coating on the surface, don't about the dyed stuff, don't seem to have it here just try some and see what the result is

[Dennis]

Yes as Bob says, it is not soluble enough in water, but a saturated solution in meths is fine. The purple colour is of no consequence, but it is best brushed on a slightly warm piece.

This raises the problem of flammability, because you need to keep the bottle well away from a naked flame.

You can also use any bought in liquid flux.