The word Paste as it relates to antique rhinestone jewelry is the term that came to be used to describe manmade or natural rhinestones of the 18th and 19th Century. Natural rhinestones of this period were fashioned and faceted from clear rock crystal quartz.
Paste rhinestones were used in replicas of fine jewelry commissioned by the wealthy. These glass jewels were well designed and made as carefully as precious stones, in a myriad of colors. It is believed, they were named pastes by jewelers of the era, to denote the stones were fakes that were pasted into jewelry or that the stones were fakes and made from a leaded glass paste. Neither theories are definitively documented. Pastes took on a life of their own and became highly desirable in their own right.
Leaded glass, of course, would result in crystal. Adding a metal coating or foiling to the backs of crystal makes them highly reflective. The foiling of early crystal rhinestones will most often be a silver colored coating, versus a gold coating and in closed back settings. The faceting from one stone to another will not be perfectly matched, or you may see tiny edge bites and irregularities that were not polished smooth. Early hand cut rhinestones will usually feel sharp on the edges and facets. You cannot tell the amount of lead used in early Paste stones, however if they are early faceted stones cut from rock crystal, they will test as quartz with a gem tester.
As jewelry styles changed around 1850, Pastes were made to primarily imitate diamonds. This change brought about a unique Paste rhinestone, called the Black Dot Paste. A tiny black dot was painted on the bottom underside of the stone to mimic the open culet of early diamond cuts, which often look dark and black. Early diamonds did not come to a bottom point, but rather, the facets joined around a flat area on the bottom. Black Dot Paste is fine quality paste, usually set in sterling silver. The shape of fake diamond Paste stones will usually have a high crown with a small table or be rose cut in shape.
In the late 19th Century, machine cutting of crystal rhinestones came about and early 20th Century crystal rhinestones were used with and without foiled backs. Some glass stones may appear to be crystal because they are fire polished. The difference can be seen by the prismatic qualities of crystal. Fire polished glass will have rounded, smoother edges and is not as heavy as crystal. Under a loupe, Pastes will rarely have bubbles, while glass almost always will. Touch can also help identify crystal in that it will remain cool when touched to the cheek or lips, while glass will warm.
The use of the word Paste today is often confused with the word Pavé. Pavé settings are stones set very close together. The stones cover the underlying surface, like paving a street of cobble stones. In better pieces, prong settings are used and in less expensive pieces, the stones are simply glued in.
The use of the word French Paste can also be misused to describe rhinestone Pavé settings that are set in sterling silver, usually of European manufacture. The word rhinestone was actually derived from the French phrase caillou du Rhin which translates to stone of the Rhine. Stones of the Rhine River are where the rock crystal quartz was found and to qualify as true French Paste, the stones should test positive as rock crystal. However, the French also made early Pastes and continued with pastes into the 1920’s and 30’s. The most commonly used are known as demi fins.
Pastes are also sometimes confused with old Mirror Backed Rhinestones and Vauxhall Glass Rhinestones, but those are studies for another day..
You can come to recognize Pastes by viewing the many authenticated pieces available on reputable jewelry sites, or for an in depth study of Georgian jewelry, "Antique Paste Jewellery" by Malcolm David Samuel Lewis is recommended reading.