New cut glass made with stone wheels is very similar to vintage American Brilliant Period cut glass made from around 1880 to about WW I.
During this era, the first shaping cuts were made by dripping an abrasive on stone wheels. The abrasive did the actual cutting as the glass was pressed against the wheels. Cuts were progressively smoothed out by using different grits of abrasive and wheels with different surfaces including wood and cork. This labor intensive multistep process produced a very smooth surface with virtually no grooves or pitting (Fig. 7).
In contrast, the great majority of modern reproduction cut glass was made in one step with coarse steel grinding wheels or diamond edged wheels. These modern wheels cut glass quickly and easily without abrasives in one pass. The rough cuts were only lightly smoothed. Modern cut glass made with the new wheels has been relatively easy to identify because of the obvious grooves (Figs. 5-6) remaining in the unpolished cuttings.
A large glass shop based in Turkey has brought back stone wheel cutting and hand polishing. The price list shown in Fig. 3 describes four different grades of finishing available. The highest grade, "Slow stone cutting with hand polishing," is nearly comparable to the hand-finished cutting found in authentic Brilliant Period cut glass. This top grade is twice as expensive as the introductory grade.
How good is the new glass? The new lamp by this company shown in Figs. 1 and 2 was good enough to fool an advanced collector into paying over $2,000. The wholesale cost was under $500.
Never rely on a single test when evaluating American Brilliant Period cut glass. Use a variety of different tests before forming a conclusion on age and quality. One of the tests you should use is ultraviolet light. Authentic American Brilliant Period cut glass will almost always fluoresce a green-yellow. Most reproduction cut glass has no reaction. Some new cut glass from Turkey will fluoresce pale yellow, but not green.
Another good test of quality is to carefully inspect the entire pattern for design flaws. Most vintage American patterns were cut by eye. Less skilled modern cutters often have trouble correctly spacing a pattern. Flaws in layouts like the overlapping rays in Fig. 4 are virtually never found in vintage pieces, only reproductions.
Acid signatures are the least reliable test of age. All the marks from vintage makers have been forged for many years. Many of these forged marks have names of cut glass companies which never used acid stamps such as Empire and Mt. Washington which used paper labels only.