Stone setting is the job of holding a gem in metal so it stays put for decades. The setter cuts a seat for the stone, places it, and then moves metal over its edge with pushers, hammers or burnishers. The style chosen decides how secure the stone is, how much light reaches it and how much risk the stone faces while being set.
The seat
Almost every setting starts with a seat, a ledge cut into the metal that matches the angles of the stone's pavilion and girdle. Setters cut seats with burs in a flexible shaft or micromotor. A seat that is too shallow leaves the stone loose. A seat that is too tight puts pressure on the girdle, and pressure is what chips stones during setting. Fitting the seat accurately is most of the work.
Prong setting
Prongs are metal claws, usually four or six, that rise from a basket or head and bend over the girdle. The setter notches each prong at girdle height, drops the stone in, and pushes the prong tips down evenly so the stone sits level. The tips are then filed and rounded.
Prongs let in the most light and show the most of the stone, which is why the round brilliant cut is so often set this way. They are also the least protective style. Prongs wear thin over years and can snag on fabric, so a periodic check is part of owning a prong-set ring.
Bezel setting
A bezel is a collar of metal that surrounds the stone. The setter fits the stone into the bezel cup and then pushes and burnishes the top edge inward until it grips the girdle all the way around. Bezels protect the edge of the stone better than any other common style, which makes them a good choice for softer gems and for cabochons. They hide a little of the stone and let in less light from the sides.
Flush setting
In a flush (or gypsy) setting, the setter drills a hole straight into the metal, cuts a seat inside it, drops the stone in so its table sits level with the surface, and burnishes the surrounding metal over the girdle. The stone sits low and well protected. Flush settings suit men's rings and bands, and they work best with hard stones because the burnishing puts force on the girdle.
Channel setting
Channel settings hold a row of stones between two parallel walls of metal. The setter cuts a groove along the inside of each wall, slides the stones in so their girdles sit in the grooves, and then tightens the walls. Round and square stones of matched size are used, and calibrated cuts help because each stone must fit exactly. Channels give a smooth edge with nothing to catch, but a damaged wall can loosen several stones at once.
Bead and pave setting
Bead (or grain) setting uses tiny balls of metal raised from the surface with a graver. The setter drills and seats each stone, then cuts into the surrounding metal and pushes up a sliver that is rounded into a bead with a beading tool. Each bead holds the edge of one or more stones.
Pave is bead setting done over a whole surface, with small stones placed so close together that the metal almost disappears. Micro pave uses very small stones and is usually set under a microscope. Pave looks bright and continuous, but the beads are small, and stones can loosen if the piece takes a hard knock.
Other styles
A few more methods turn up on the market:
- Tension settings hold the stone between the ends of a sprung band; they need a very hard stone and precise sizing.
- Invisible settings fit grooved square stones onto a hidden metal framework so no metal shows from the top.
- Illusion settings surround a small stone with bright metal to make it look larger.
The look and wear of each of these from the buyer's side are covered on the gemstone settings page.
Tools of the setter
Setters work at a bench with a ring clamp or a setting block (a ball vise) that holds the piece steady. The usual kit includes:
- burs in many shapes for cutting seats
- gravers for cutting metal and raising beads
- prong pushers and bezel pushers
- burnishers to smooth metal over the stone
- hammer handpieces for bezels in hard metals
- beading tools with cupped tips in graded sizes
- a loupe or a stereo microscope
Risks to stones
Setting puts force on a stone, and some gems handle it badly. Stones with perfect cleavage, such as topaz, kunzite and tanzanite, can split along a plane if pressure hits the wrong spot; see cleavage in gemstones. Diamond is the hardest gem but still has cleavage, and a blow to a thin girdle can chip it. Soft or porous materials like opal, emerald and pearl need gentle settings, and emeralds also carry filled fractures that heat and pressure can disturb.
Heat is a second danger. If a ring needs soldering or sizing after setting, many stones must come out first. Treated stones are a special case: fracture-filled and glass-filled gems can be damaged by torch heat or pickling, which is why disclosure of gemstone treatments matters to the bench jeweler as well as the buyer.
Frequently asked questions
Which setting protects a stone best?
A full bezel or a flush setting gives the most protection because metal surrounds the girdle. Prongs protect the least.
How often should prongs be checked?
Many jewelers suggest an inspection about once a year, or sooner if the ring catches on fabric or the stone moves.
Can any gem be set in a tension setting?
No. Tension settings squeeze the stone, so they are normally used only for very hard, tough stones such as diamond, sapphire and ruby.
Why do some stones have to be removed before a ring is resized?
Sizing involves heat and pickling, which can crack, discolor or damage heat-sensitive and treated stones. Removing them avoids that risk.