If you get your wire from a dedicated supplier who knows exactly what alloy of wire you're buying - because they buy it in bulk and have the data on what each individual alloy contains mineral wise - you're safer as far as knowing the material content.
While yes - copper wire is 'pure copper' no not always - especially if its wire that's been salvaged and has been melted down & remade into wire - there's going to be trace minerals in the alloy. dealing with good wire distributor who knows the alloys will be able to tell you what is in the wire you're buying.
for every metal there's at least a dozen if not more different alloys - for steel there's over a thousand different alloys.
"Surgical stainless steel" more often than not contains nickel - the element known to cause most allergic reactions to jewelry. Unless you're buying wire that has a known content for being #%of x and #% of y - then its a guessing game.
My supplier for wire sells copper that is per them - pure copper. Most of the bronze i use is phosphor bronze which means its copper, tin & phosphorous; though there's also a pretty sulfur bronze (copper, tin & sulfur); then I also use nickel silver (copper, nickel & zinc - no silver)...for aluminum I use alloy 5356 which contains: silicon, iron, copper, beryllium, zinc, manganese, titanium, magnesium, chromium and most importantly Aluminum. All of those 'other' components in 5356 alloy Aluminum add up to less than 1% but they're still included in the mixture.
Knowing the alloy of the specific wire you're using in any given piece will help you determine its metal content.
Shopping from a good wire distributor who knows the alloys they sell -will be able to point you to the mfg and probably will hand you the MSDS and or the ASTM-testing paperwork for little to no hassle some of these are even available online through the various associations whose job it is to work with these metals in more original purposes (welding/construction) because workers are around the wire in dust, heat, etc they know what's in their metals so they know what precautions if any their workers need to take.
Unfortunately craft stores/suppliers like blue moon beads/fire mountain gems simply don't care about anything but their own bottom line.
KNOW your product - inside & out - that's what it boils down to. if you'd like info on the supplier i use - feel free to send me a convo
-frawggie-
