Silver Jewelry Heating Effect

Hi

Can anybody help me on soldering the Sterling Silver jewelry. I
tried soldering the polished pcs. but it changes the colour ( Patch)
I am using S-88 silver alloy from United Metals.

I intend to make the silver jewelry having anti- tarnish property
also I dont wanna rhodium plate the pcs. as it increases the cost of
the pcs.

Thanks in advance.
Dinesh