Purple Stains on Silver

**BeJewellery** · 28-02-2010, 02:21 PM

Help!

My last couple of projects (simple sterling rings) have strange purple stains on them.

Whilst i'm filing the rings after soldering, pickling and shaping the horrible purple stains appear! I've found that putting them back in the pickle for a while and a bit more filing gets rid of them, but I would like to know what causes them so I can try to prevent it happening again and again.

Wendy

**lynnm** · 28-02-2010, 03:20 PM

it's not fire stain is it?

**BeJewellery** · 28-02-2010, 03:24 PM

If it is fire stain, should I just leave it in the pickle longer?

Sorry for the stupid questions but I consider myself to be a newbie!

**SilverKiss** · 28-02-2010, 03:30 PM

Originally Posted by BeJewellery

Help!

My last couple of projects (simple sterling rings) have strange purple stains on them.

Whilst i'm filing the rings after soldering, pickling and shaping the horrible purple stains appear! I've found that putting them back in the pickle for a while and a bit more filing gets rid of them, but I would like to know what causes them so I can try to prevent it happening again and again.

Wendy

Hi Wendy.

My first conclusion is that it's firestain - a deeper form of the surface oxidation that you get when you heat the silver (sort of). I absolutely expert at getting it, so feel a bit sheepish about advising on not getting it, but on the basis that I'm learning from my mistakes, here goes.

Make sure that the piece is well fluxed - that's not to say that you need to put loads on, just get it all over. That helps protect it. Borax is fine, but I've been really impressed with the Magic Boric that's on the market here now.

Try to heat the peice for as short a time as possible. Obviously, you need to get it hot enough for the solder to flow, but do it quickly.

If the solder won't flow, you can give it a nudge with a soldering pick but after that, stop. Don't just keep heating - take it out, re-clean it, reflux and start again.

Make sure you torch is big enough to do the job - a small torch on a big item might get it hot enough eventually, but you just be oxiding the metal in the meantime.

Well done for spotting it early on - I often don't get to see my firestain until I've started polishing. It's much easier to see the firestain if you hold the work against a plain white background (eg sheet of paper).

Hope that helps.

The only other thought (becuase you mention purple): you don't have any liver of sulphur hanging around, do you? In low doses, that can produce a purple stain.

**SilverKiss** · 28-02-2010, 03:32 PM

Originally Posted by BeJewellery

If it is fire stain, should I just leave it in the pickle longer?

Sorry for the stupid questions but I consider myself to be a newbie!

No, you really need to abrade it. Not usually necessary to resort to a file - emery will usually do it.

**lynnm** · 28-02-2010, 03:54 PM

having been the first to answer I will leave it with the master... I am a newbie to and really couldn't say as much as has been, so there you go!

**BeJewellery** · 02-03-2010, 01:21 PM

Thank you for all the help

Originally Posted by SilverKiss

Hi Wendy.

Make sure that the piece is well fluxed - that's not to say that you need to put loads on, just get it all over. That helps protect it. Borax is fine, but I've been really impressed with the Magic Boric that's on the market here now.

I normally only flux the area I'm soldering, should I flux the whole piece

**Lindyloo** · 02-03-2010, 01:47 PM

That's a good question. Because we were taught at college, if I can remember correctly, that solder flows on the areas where you have fluxed. So if you flux further than the desired solder area, won't it tend to flow to places where you don't want it? I am interested in hearing the answer to this.

**SilverKiss** · 02-03-2010, 02:06 PM

bit of a swings-and-roundabouts debate, this. Yes, flux will help the solder flow, but it will also protect against firestain. Depends which you see as the greater problem.

Which is the greater problem will depend on how quick you are at doing the job and how much excess solder there is to slop around the place.

If the join to be soldered is nice and clean and the faces to be joined are nice and flush, you really don't need much solder, and it will be drawn into the joint by capillary action. Problems will occur if you have a big gap and try to use solder as a filler. What's a big gap?: if you can see light between the faces to be joined, the gap is big!

That's the theory, anyway. I certainly can't claim to get it right every (most?) time, but it's soooo satisfying when you get a really neat join with virtually no clean-up to do.

For really tricky jobs there are other firestain protectors but I wouldn't recommend them as a way of getting over poor technique.