A retail customer wears a new solitaire for three weeks, washes her hands, and the center stone is gone. The store blames the customer. The customer blames the store. The store sends the piece back to the factory, and the QC record shows the piece passed a visual check before shipment. The gap is that visual check alone does not catch a stone that is seated but not locked. The pull test and ultrasonic soak are the steps that catch it, and they are the steps that get skipped when a wholesale run is rushed.
The four-step stone security check
Every stone-set piece that leaves our shop passes four checks, in order. Step one is the loupe check at 10x: every prong tip is closed over the crown, no prong is bent, no stone is rocking in the seat. Step two is the tweaker check: a wooden or plastic tweaker taps the stone girdle; a secure stone does not move. Step three is the ultrasonic soak for 5 minutes in warm water and detergent; any stone that is only wedged, not locked, will usually loosen. Step four is the pull test: a small prong lifter hooks under the girdle and applies gentle upward pressure; a secure stone does not shift. We log each result on the QC sheet, the same format we use in final QC loupe ultrasonic checks.
Why the ultrasonic catches what the loupe misses
A stone can be visually seated, with every prong closed, but the seat angle is slightly off and the stone is only touching at two points. Under loupe it looks fine. In the ultrasonic, the 40 kHz vibration loosens that marginal contact and the stone shifts in the seat. We see this most often on moissanite setting tolerance girdle pieces, where the girdle is thinner than a diamond and the seat has to match exactly. The ultrasonic is not optional; it is the test that produces the QC record a retail brand can hand back to a customer. The IGI setting guidelines also recommend a post-set ultrasonic check for any stone under 3 mm, where a loose seat is hard to see.
Pull test force and what secure means
We do not yank. The pull test applies about 200 grams of upward force on a 1 ct stone, 100 grams on smaller stones. That is enough to reveal a loose seat without bending a prong. A stone that shifts under that force goes back to the setter. A stone that holds passes. We pair this with prong tightness check stone setting, because a tight prong on a rocking stone is still a failed piece.
Channel and pave stones need a different check
Channel-set stones are checked with a feeler: a thin steel probe runs along the channel to confirm no stone is sitting proud of the rail. Pave stones are checked one by one under loupe, and every bead is confirmed closed. We do not ultrasonic a heavily pave piece more than once, because repeated ultrasonic exposure can loosen micro-beads over time. The same logic applies to channel setting wear teeth longevity for wedding bands.
What we log and what the retail brand gets
Every piece ships with a QC slip that lists: loupe pass or fail, tweaker pass or fail, ultrasonic duration, pull test result, and the inspector initials. If the retail brand wants a third-party report, we can attach photos. This is the same documentation process we use in qc photos before shipment jewelry, and it is what turns a stone fell out dispute into a documented record.
FAQ: Stone security pull test
How long should a stone stay secure after setting?
A properly set stone should not need tightening for 12 to 24 months of daily wear. If it loosens in the first month, the seat or the prongs failed QC.
Does the ultrasonic damage the stone?
No for diamond, sapphire, ruby, moissanite. Yes for opal, emerald, pearl, turquoise, and any stone with fractures filled. We skip ultrasonic on those and rely on loupe plus pull test.
Why does my stone still fall out after passing QC?
Usually the prong tip was not burnished over the crown. It looked closed under loupe but was not actually locking. We burnish every prong tip after set, which we cover in prong setting diamonds safely.
How often should a retail customer have the stone checked?
Every 12 months on a daily-wear ring. We include a free check on any piece that comes back to us, which is the same step in final packaging inspection jewelry shipment.
If your wholesale line has a high stone-loss return rate, send us the spec and the failure rate. Our custom manufacturing QC team will run the four-step check on every piece and ship the QC slip so your storefront has the record before the customer calls.
Independent background on moissanite — how its hardness and refractive index compare with diamond — is documented in the Wikipedia article on moissanite.
Frequently Asked Questions
How do I verify a factory before placing a bulk order?
Request a production video, business license, export records and a paid sample run. A factory that accepts a 50-piece test order is usually a real manufacturer.
What payment terms do you offer?
30% T/T deposit with the balance against the bill of lading. This protects both sides on first orders and can move to net terms after a track record.
What is your normal reject rate?
3–5% under 10x loupe inspection for cast and set pieces. Defective units are replaced free in the next shipment.
Where is the factory located?
Wuzhou, Guangxi, China—the core lab-grown and moissanite manufacturing cluster. Shipments go via Guangzhou or Shenzhen ports.
