Is there good and bad stonesetting?
As stonesetting is a manual craft, the skill of the craftsperson influences the quality of the work heavily. This epresses itself both on the aesthetic level and on the technical level. In simple terms, a jewel should both be beautiful and well made.
Is it beautiful?
If small stones are set in a straight line, is any of them out of alignment? Is the distance between the stones regular, or are some closer together or further apart?
If they are set in a curve, do the stones follow it smoothly?
When watching a field of small stones from one viewpoint, do any of them look darker or brighter than the rest? If they do not, and some of them appear to ‘blink’ when tilting the jewel, they are not set horizontally.
Does the metal in between and around the stones reflect the light, multiplying the brilliance of the stones? The amount of care given to the metal in between is very distinguishing of good setting work. Properly executed, the reflections on the metal enhance and highlight the gemstones. Poor work will make the stones seem dull and ‘buried’ inside the metal instead of shining above it.
Is it well made?
None of the stones should be loose. A loose stone will wear away the metal, and eventually fall out.
No stone should touch another one. That will certainly damage the gems. A stone should only ever be in contact with metal. That can absorb the force of impacts by bending, instead of the stone itself breaking.
Are there any sharp corners on the jewel that will catch on fabric? Sometimes sharp hooks can even pierce the skin. This is clearly a major defect.