HELP: Where is this discoloration coming from on my silver?!?!

Hi all,
This is my first post, and came to this forum to hopefully figure out a mystery!
Sometimes I end up with this weird, oily-looking, discoloration on my silver. It seems to appear after I solder and pickle. I notice it after I clean it up upon removing it from the pickle. I thought it was maybe something left on my buffing and polishing bits, so I've replaced them all. It still shows up! I thought it was maybe my pickle. I changed it. It still comes sometimes! (I used to use a homemade vinegar and salt pickle, but I've now switched to a better-performing pickle: sparex no.2) I sand and sand and buff and tumble to try to remove the discoloration, but it remains! It might not stand out to everyone, but it's very obvious to me. It drives me crazy that this happens and I don't know why or how! Any ideas???? I've scoured google to no avail. HELP PLEASE! (attached is pictures of one case)
Thank you in advance!
Heather
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It's firestain. Searching this forum will yield many results for ways to avoid it in the first place, and solutions for when it happens!

Yes, the bane of working with silver, due to oxides of copper quite deep below the surface, hence the need for aggressive removal with abrasives.
You can help to avoid it by shortening the soldering time, and fluxing the whole piece. Dennis.

Quote:

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Originally Posted by mizgeorge

It's firestain. Searching this forum will yield many results for ways to avoid it in the first place, and solutions for when it happens!

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Thank you, mizgeorge!

Thank you, Dennis!