Green smoke when soldering with sterling silver

[Bine]

Welcome to the forum Bine,
If your silver is burning then it is probably covered with a coating of plastic. Here in the UK some suppliers send us sterling silver covered this way to stop it tarnishing while in stock. When soldering, it is important to clean all surfaces manually before commencing. You can use abrasive papers or steel scraping tools. Solder joints and the solders all need to be cleaned this way, I use a three square steel scraper for this purpose. All solder joint surfaces need to be fluxed and all solder pieces also. I use borax as my flux. Here in the UK we have a Borax cone and borax dish and just add a little water before mixing the borax into a milky substance which is the added to the solder areas by means of a small paint brush. I cut small solder pieces and dip them in the borax before adding them to the solder joint.
Sorry if this is too much info!
James

Thank you for your answer.
I use sulphuric acid 14% before I solder to clean the silver but it doesn't seem to work. I also got flux for solder pieces and silverpaste with flux in it. That's why I don't understand why it seems like there is a "coat" of something on the silver.

[CJ57]

Hello Bine
I think James is correct and there is a plastic cover on your silver and you must remove this first, you should be able to peel it from the silver quite easily and then rub the area to be soldered with an abrasive paper. There is no need to use sulphuric acid especially if you have not removed the plastic covering!
Whichever form of solder should then work, either small pieces with the flux you have chosen or silver solder paste. Clean silver sheet should never go on fire

[mizgeorge]

Solder paste contains organic binders which burn away during use - this can give a green flame. It's important to heat the metal, not the solder, however, as if you use the flame directly on the paste it will burn and become useless.

[Bine]

Solder paste contains organic binders which burn away during use - this can give a green flame. It's important to heat the metal, not the solder, however, as if you use the flame directly on the paste it will burn and become useless.

I think you are right because I only experience this when using solder paste. Thank you for helping me!

[Bine]

Hello Bine
I think James is correct and there is a plastic cover on your silver and you must remove this first, you should be able to peel it from the silver quite easily and then rub the area to be soldered with an abrasive paper. There is no need to use sulphuric acid especially if you have not removed the plastic covering!
Whichever form of solder should then work, either small pieces with the flux you have chosen or silver solder paste. Clean silver sheet should never go on fire

Thank you! I will try abrasive paper and see if if works.