The alloy or the resin is the bone. The finish is the garment the customer photographs. Bright nickel, antique brass, gun black, a pad-printed logo and a laser mark are different processes with different rub, sweat and salt-spray lives. Specifying “gold” without a process is how two factories ship two colours.
Metal: decorative versus protective
Bright nickel, chrome or a high polish is a mirror. It photographs well on stage and streetwear. It fingerprints and scratches; a lacquer (often called a clear or “spray lacquer” in mill English) is not optional if the button will be handled.
Matt comes from sandblast, chemical etch, or matt nickel/gold plates. It hides micro-scratches and suits tailoring.
Colour families mills actually run: gold and imitation gold; nickel, chrome and silver; antique coppers (green, red, dark); gun and black nickel. Fashion colours (blue, pink, fade stacks) are alloy plates, PVD or spray — ask which. Two-tone “clash” buttons are often a base plate plus a filled colour (resin drop, PVD mask) plus laser and a final lacquer.
Protective stacks are not the same as colour. Steel jeans parts typically want copper then nickel then chrome; brass may take nickel or imitation gold plus lacquer. Chrome-free passivation (titanium or zirconium chemistry) is the EU-kids conversation. Black oxide on steel is a workwear look, not a fashion gold.
PVD (vacuum) is the thinner, cleaner decorative route some mills use instead of a heavy wet plate. It is still a finish spec, still needs adhesion and wear tests.
Non-metal faces
Urea and polyester buttons are dyed in the mass or surface-dyed, then polished. Pad print, heat-transfer marks and laser engraving sit on top. Laser is the clean logo method on resin and on some metals; depth and colour fill are extra lines on the quote.
Spray paint and enamel fills chip if the button flexes or if the wash is industrial. Pearl and foil effects are coatings, not the substrate.
What to test with the finish, not after
Rub (dry/wet), sweat, wash, and — for metal — salt spray and nickel release on skin-contact articles. A beautiful antique that sheds oxide onto a light coat is a finish failure, not a “fabric dye” claim.
Write the stack: “Zamak 3, antique brass plate, clear lacquer, laser logo, EN 1811.” That is a button. “Vintage gold” is a mood board.
Two-tone alloy buttons are several operations (base plate, colour fill, laser, lacquer). Each step can fail independently: fill chips, laser burns through a thin plate, lacquer yellows. Approve a sealed card under D65, then wash and rub that card — not a hero photo.
Antibacterial or “cool” plates are extra chemistry. They inherit the RSL. They do not replace nickel-release testing.
The face is the product the customer photographs. The stack is the product that ships.