Dritz-type buttons have aluminum shells (fronts). They don't rust. Machine cover buttons (the ones I sell) can have aluminum, rust-resistant, or aluminum shells. I started stocking non-rusting shells exclusively after I washed a dress with steel buttons, and the rust went right through the fabric. This is not my photo, but here is an example:
Steel is cheaper, though -- I sell steel shells to this company
. I keep on them on hand just for them, but now I'm wondering if I should stock steel shells as an option for everyone.
So... pretend you own a button machine. You want #45 shells (1 1/8") -- steel
shells are .03 each
shells are .04 each
. Which one will you buy? For the record, #45 aluminum shells from here work out to roughly .16 each.