I'm sure you know all of this, but figured it might help the OP to contextualize your post:
The element Nickel (Ni) is different from what is normally called Nickel, or nickel silver (also called German Silver), in the pipe world, which is an alloy, which is about 20% Nickel, 60% Copper and 20% Zinc.
I'm not sure what you were working with, but there's a big difference between working with Nickel and working with Nickel Silver. Of course, it also depends on your allergies, since some are allergic to nickel, but too much copper in the right circumstances can also cause allergic reactions.
Sykes
True, for context… it is common in the jewelry industry for jewelers to develop an allergy to nickel from just working with white golds, which is merely 25% nickel at most and 10% in the least alloy. It is mandatory in stores to have protections from the metal dusts. The metal I used for a bit was german silver, which is a white bronze we use to make mock ups because it melts so easily and you can build prototypes very easily. I worked with this metal when designing eyewear henges for the industry. In storefronts, everything has vacuum ports and dust collectors to minimize risks. No dust escapes into the air. When I built my own home studio in a separate building from the home, I priced systems at 9 to $10,000 and then put it off till later. 8 years later and I still haven’t, and I’m paying the consequences. All of that time, white gold was the only metal with nickel I was using.
I have had some pure nickel stock that I was going to use for a project, but it is an impossible metal to work with. So, my exposure to that was very brief.
About four years ago, I started getting rashes and a cough, and after dermatologists, general doctors, ran out of options, they sent me to an allergist. And, I’ve had extensive tests done to find every allergy. The type I have is not one that is born with, but developed from exposure. The allergist believes that it is the alloys mentioned that cause the most exposure. Even buttons and those metal studs in bluejeans cause me to have reactions now.
Copper is ify also. Pure copper is rare to come across. Most of that also has a touch of nickel.
Unless you are alredy allergic to nickel, touching a german silver band is not going to give you an allergy. But, if you are heating, sanding, and polishing german silver you are breathing the dust, unless you have a hepa filtration dust collection system with ports to collect dust as you work.
So, for a small time home studio, or working in a garage, I do not recommend nickel silver for band production.
Not when silver is very affordable. Sterling is $30ish an oz, and every part, scrap, and dust can be easily melted and reused. Even if one used Riogrande to buy sheet stock to make bands, you can send scraps back to Rio when you place your next order.
Now, this is my experience. I am not narcissistic enough to think that I have the power to stop anyone from doing what they are going to do. I set up my studio without a dust system against better advise. Guys are hard headed. I know this. It is your risk. However, I merely advise that people taking the risk make themself aware of the risks.
But, do consider sterling. Many people look at metal prices and turn away before they actually give it a chance. Sterling is so easy to manipulate and makes beautiful bands and spigots. Plus, you get your money back when make a sale. Unless your devoted to serving the homeless decorating their cobs, sterling is a very reasonable choice.
And, I have some books to recommend to get you started. The Complete Metalsmith by Tom McCreight. He uses easy to understand drawings, and many tools can be made easily. That is the best book to get started with. I can rec more if needed, just DM me.