316L surgical steelMATERIAL

A specific medical grade of stainless steel containing chromium, nickel, and molybdenum in a precise ratio. The L stands for low carbon. 316L is the standard alloy used in pacemakers, joint replacements, orthopedic implants, and surgical instruments because it has very low nickel release in contact with human tissue. In jewelry, 316L is the safest non precious base metal option for sensitive skin.

Why it matters: generic surgical steel labels can hide lower grades. 316L specifically is the medical designation. If a jewelry brand does not specify 316L, the steel may contain higher nickel.

14K gold platingFINISH

A thin layer of 14 karat gold electroplated onto a base metal. Standard fashion plating is 0.05 to 0.1 microns thick and wears off within weeks of daily wear. Higher quality plating runs 2.5 plus microns, roughly 25 to 50 times thicker. Caeli pieces use 2.5 plus micron plating over 316L stainless steel.

What to ask before buying: what is the plating thickness in microns, and what is the base metal underneath. A brand that cannot answer both is hiding something.

VermeilREGULATED TERM

A regulated FTC term (16 CFR Part 23, Subpart C, Section 23.5) reserved for gold plating over a sterling silver base. To be legally called vermeil in the United States, a piece must have a sterling silver base AND a gold layer of at least 10 karat fineness AND minimum thickness of 2.5 microns of fine gold. Gold over brass, copper, or stainless steel cannot legally be called vermeil regardless of plating thickness.

Common misuse: many fast fashion and DTC brands label gold plated brass or steel as vermeil. This is not allowed under FTC rules. Read our full FTC vermeil breakdown.

Gold filledFINISH

A thicker gold layer mechanically bonded (not electroplated) onto a base metal, typically brass. By US standard, gold filled must contain at least 5 percent gold by weight, marked as a fraction (for example 1/20 14K GF means 5 percent of total weight is 14K gold). Gold filled holds up significantly longer than standard plating but uses brass as the base, which contains nickel and can still cause reactions in highly sensitive individuals.

Solid goldPRECIOUS METAL

Jewelry made entirely from a gold alloy throughout, not plated. Sold by karat: 24K is pure gold (too soft for most jewelry), 18K is 75 percent gold, 14K is 58.3 percent gold, 10K is 41.7 percent gold. Solid 14K and 18K gold are the gold standard for fine jewelry but priced 5 to 20 times higher than gold plated alternatives.

HypoallergenicCLAIM

An unregulated term in the United States. There is no FDA or FTC standard for what hypoallergenic must contain. The word can be applied to anything a brand chooses to apply it to. In practice, the most reliably hypoallergenic jewelry uses 316L surgical steel, titanium, or platinum as the base metal, all of which have very low nickel release.

What to verify: the base metal. Hypoallergenic over brass or copper means very little once the plating wears through. Hypoallergenic over 316L or titanium means something.

Nickel allergyMEDICAL

A form of allergic contact dermatitis triggered by skin contact with nickel ions. Affects roughly 10 to 20 percent of women and 1 percent of men in North America. Symptoms include redness, itching, rash, blistering, and skin thickening at the contact site. Once developed, nickel allergy is typically lifelong. Treatment is avoidance, not cure. See the American Academy of Dermatology guide for full details.

TarnishWEAR PATTERN

The dark discoloration that forms on the surface of certain metals through oxidation when exposed to air, sweat, and humidity. Sterling silver tarnishes (forms silver sulfide). Brass and copper tarnish. Stainless steel does not tarnish. Plated jewelry tarnishes when the plating wears through and the base metal underneath oxidizes.

MicronMEASUREMENT

A unit of thickness equal to one thousandth of a millimeter. In jewelry, plating thickness is measured in microns. Standard fashion plating is 0.05 to 0.1 microns. Higher quality plating is 1 to 3 microns. Vermeil requires a minimum of 2.5 microns. The thicker the plating, the longer the gold layer survives daily wear.

Closed collectionPRODUCTION MODEL

A production model where a design is made once, in a defined number of pieces, and never reproduced after that run sells out. Distinct from limited edition, which often just means a brand label rather than a true production cap. Caeli operates as a closed collection: every design is produced in exactly 100 pieces, then permanently retired.

FTC jewelry guidesREGULATION

The US Federal Trade Commission rules governing how jewelry can be marketed and labeled. Found in 16 CFR Part 23. The rules define what terms like gold, vermeil, gold filled, gold plated, sterling, and platinum can legally mean on product labels and marketing. Full text on eCFR.

Contact dermatitisMEDICAL

Inflammation of the skin caused by direct contact with a substance that triggers an allergic or irritant response. Allergic contact dermatitis from jewelry is most often caused by nickel, less commonly by cobalt or chromium. Symptoms appear within hours to days of contact and resolve when the trigger is removed.