“Metal button” is a shop-window phrase. The mill needs an alloy, a construction and a finish. A four-hole brass sew-on, a Zamak shank with a crystal, and a steel jeans tack button do not share a tool, a plater or a test plan.
Alloys in plain language
Brass (copper-zinc) is the adaptable stamper. Yellow brass (often 65 copper in Chinese mill talk) draws, engraves and plates well. It is the honest metal for better jeans buttons, some sew-ons and parts that must take a crisp logo. It tarnishes; the plate and the lacquer are the product the customer sees.
Zinc alloy (Zamak / #3 zinc-aluminium) is the die-casting metal. Low melt, fine detail, cartoon shapes, deep logos, fashion shanks. Cost sits below brass for complex forms. Strength is modest. Impurity control (lead, cadmium, tin) is a corrosion and compliance issue, not a footnote.
Stainless steel (304 as the apparel default) is the corrosion answer. Little or no decorative plate, good for outdoor and workwear, friendlier on nickel-release programmes when the surface is well finished — though “stainless” is not a legal nickel waiver. It is harder to make look like costume jewellery.
Aluminium is light and anodisable. Easy to crush. Use it when weight matters, not when a jeans waistband will be yanked daily.
Carbon steel is strong and cheap and rusts. Many value snaps and eyelets are steel under copper-nickel-chrome. The stack is the corrosion system.
Constructions buyers mix up
- Sew-on metal — holes or a shank, thread attached. Tailoring, shirts, fashion jackets.
- Jeans / tack button (工字扣) — cap plus tack (nail), riveted through denim. Not a sew-on.
- Press snap — four parts and a spring. Not a button.
- Rivet — cap plus tack for reinforcement, not a closure.
High-end tailoring still likes brass with a thick, well-lacquered plate. Mass fashion likes zinc with a pretty PVD or antique. Outdoor likes stainless. Kidswear likes the mill that can show OEKO-TEX STANDARD 100 Class I and a nickel-release report, not a “gold colour.”
What to put on the spec
Substrate + construction + finish + tests: “Brass tack button, 20 L, antique nickel, salt spray and EN 1811 on skin-contact lots.” Plating thickness talk in mill catalogues (tens of micrometres on better brass, thinner fashion zinc) is a starting point, not a certificate.
Price follows the metal market. A “gold button” that was zinc last season and brass this season is two products.
Needle detection: stainless programmes are often sold as detector-friendly because there is no thick plate stack to confuse a needle scan — still confirm on the brand’s machine. Fashion zinc with a heavy decorative plate is a different detector story.
Kidswear wants Class I chemistry and a pull-off that matches GB 31701 / the brand method, regardless of how “premium” the brass looks.
TrimGem quotes the alloy. Colour is the plate.