Cast vs Hand-Fabricated: Can You Tell From the Underside?

Cast vs hand-fabricated: can you tell from the underside?

The underside of a ring, pendant, or earring often reveals how it was made. You don’t need laboratory equipment to spot many clues. A 10x loupe, a steady light, and knowledge of what to look for will tell you a lot. Below I explain the practical signs, why they appear, and when the differences are hard or impossible to see without advanced testing.

Why the underside matters

The back of a piece is where joins, supports, and internal shaping hide. Those features affect durability, repairability, and value. For example, a hand-soldered bezel will usually be easier to tighten than a cast one that is brittle and full of porosity. Knowing the method also helps you judge whether a finish was intentionally applied or is masking a flaw.

Basic processes and their typical underside markers

• Lost-wax casting and 3D-printed wax/resin casting: Wax or resin models are burned out of an investment mold, and molten metal fills the cavity. Expect a parting line or seam where the investment met, tiny surface bubbles (pinholes), and occasional sprue marks where the metal entered. 3D-printed patterns can show layer lines or resin-support scars before finishing.
• Sand or centrifugal casting: Used for larger or lower-cost work. Surfaces often show grainy texture and more porosity. Interior surfaces are rougher compared with investment casting.
• Hand fabrication (sawing, forming, forging, soldering): Pieces are cut from sheet or wire, formed, and soldered. Look for clean solder seams, file marks, hammer marks, and tight-fitting joints where two pieces were joined. Tool marks follow logical lines—along solder joins, inside cutouts, or around bezels.

Clear visual clues to check

• Seam lines and parting lines: A thin seam down the center of a shank or element is classic casting evidence. Why? Investment molds form in two halves and leave a line where they meet. Hand-fabricated joins usually show a solder line rather than a continuous seam.
• Sprue remnants and vent marks: Small raised bumps or flattened areas where the sprue was cut off are signs of casting. Makers cut and file these away, but under magnification you can still see the footprint.
• Internal surface texture: Casting often leaves a slightly pebbled or pitted interior. Fabrication leaves linear file marks, saw kerfs, or one-directional polishing. Why? Casting is molten metal filling a mold; fabrication is mechanical removal and joining of material.
• Porosity and pinholes: Tiny holes inside bezels or under seats are casting defects. They appear because trapped gas or shrinkage occurred during solidification. A hand-fabricated piece rarely has random porosity unless poor soldering or overheating occurred.
• Solder beads and solder seams: When a jeweler solders a wire or bezel, small raised solder fillets or a thin scar remain. Those are straightforward indicators of handwork. Laser-welded seams are finer but often leave heat-affected coloration or a faint line.
• Hammer/planishing marks: Slight dimples or flattened tool marks on the inner surface mean the maker forged or planished the shape. Casting does not produce these marks unless intentionally added.
• Grain or flow direction: When metal is worked cold or hot, the grain elongates in a consistent direction. On a fabricated shank you may see a subtle grain flow when polished. Cast metal typically shows isotropic structure with no directional grain visible in finish.
• 3D-printed wax/resin artifacts: Look for tiny layer ridges or support scars inside cavities. These are most visible under magnification and point to modern print-to-cast processes rather than hand-carving.

Examples with measurements

If you inspect a 1.00 ct round diamond ring (approx. 6.5 mm bezel), the inside of a cast bezel often has tiny pits where gas was trapped. The bezel wall might be uniformly 0.7–1.0 mm thick with a faint parting line. A hand-fabricated bezel with 0.8 mm wall thickness will usually show a solder seam where the bezel end was joined and file strokes inside the gallery created while seating the stone.

On a 2.5 mm wide shank (common for engagement rings), a cast shank may have a seam that runs along the inside centerline; a fabricated shank formed from 1.5 x 2.0 mm wire and soldered will show a distinct solder joint on one side and planishing marks from shaping hammers on the opposite side.

How metal and finish change what you see

Gold alloys (14k = ~58.5% gold, 18k = 75% gold) polish quickly and can hide minor casting flaws. Platinum and palladium are dense and hard; casting defects can be less visible after heavy polishing. Silver alloys tarnish and reveal porosity as dark spots. Base metals like brass oxidize and often show more obvious casting texture. Electroplating or heavy rhodium plating can mask surface clues entirely.

When the difference is hard to tell

A skilled maker can cast a model and hand-finish it so thoroughly that evidence is gone. Conversely, a cast part can be heavily reworked to look fabricated. Modern direct metal 3D printing and CNC milling produce surfaces that mimic hand work. In these cases you may need non-destructive testing—X-ray radiography to reveal internal porosity, or metal analysis to reveal alloying traces—to be sure. Those tests are rarely available to consumers.

Practical inspection checklist (what to do and why)

• Use a 10x loupe in good light. Why: magnification reveals seams, pinholes, and tool marks.
• Look along the inside centerline of shanks and under bezels. Why: molds meet here and sprues run there.
• Check for solder fillets around wire joins and bezel ends. Why: solder indicates hand assembly.
• Scan for tiny pores or a pebbled texture. Why: that usually means casting porosity or poor burnout.
• Note uniformity of thickness. Why: cast walls are often uniformly thick; fabricated walls can vary where they were formed or soldered.
• Ask the maker for process and warranty. Why: provenance is the simplest confirmation and matters for repair.

Bottom line

Often you can tell by the underside. Parting lines, sprue scars, porosity, and pebbled interiors point to casting. Solder seams, file or hammer marks, and directional grain point to hand fabrication. High-end finishing and modern manufacturing can mask those signs. If it matters for value or repair, ask the maker or request a professional inspection. The underside is the easiest place to begin that conversation.