The metal vintage spectacles worn in pre-Revolutionary America were mostly English imports, fashioned out of steel or bronze. Bronze was superior as a metal for this purpose, since stainless steel had not yet been invented and steel vintage spectacles would oxidize (rust) in humid conditions if not properly cared for.
Silver and gold frames were also made, and imported from the silversmiths and goldsmiths of England, but these are rare (due to later melting) and have many interesting features of their own, so they are discussed in another article.
Regardless of whether they were fashioned out of steel or bronze, these metal vintage spectacles from the Colonial trade have several distinctive features which serve to mark them out from American spectacles of a later date.
Though these features are actually meant to compensate for certain aspects of poor design – which made them somewhat inconvenient to wear in practice – these vintage spectacles are still intriguing and are idiosyncratic enough to help both in identification and to foster a great understanding of the possibilities and limitations of materials technology at the time.
Eyerims and bridges of pre-Revolutionary vintage spectacles
The eyerims of vintage eyeglasses from the 17th century days of Cotton Mather and Robert Calef are mostly totally round, to match the circular lenses ground for spectacles at the time. Oval lenses were not in common use until later in the history of eyeglasses, due to the fact that it is much easier to grind a good quality optical lens in a circular shape than an oval one using handcrafting techniques (which were the only ones available at the time).
Rimless glasses were completely unknown at the time, so vintage spectacles made without eyerims date from a later period. All the vintage eyewear from 17th and early 18th century America have eyerims which completely surround the lenses. The eyerims are split so that the lenses can be inserted, and the joint is closed with a screw to keep the glass or rock crystal in place after insertion.
The eyerims are usually connected by a simple arched bridge, with no individual fitting to ensure that the lenses are each placed exactly in front of the eye they are supposed to assist. With the wide space between the eyerims, the low arch of the bridge, and the lack of nose pads, these vintage spectacles were difficult to support on the nose, which explains the form of their temples.
Lenses of metal pre-Revolutionary vintage eyeglasses
Pre-Revolutionary vintage spectacles are almost all made to correct presbyopia caused by aging, rather than vision problems present in younger people (who often viewed such problems as a sign of shameful weakness and attempted to hide them rather than correct them). This means that their lenses, whether made out of glass or rock crystal (“Brazilian pebble”) were ground either flat or with convex inner and outer surfaces, helping to correct the vision of the aging.
Despite the rather cavalier attitude of the time to finding good matches between lens power and the user's vision – with a “good enough to go on with” attitude prevailing over attempts to correct vision as nearly as possible – many metal pre-Revolutionary vintage spectacles bear a double digit number stamped into the metal, such as 20 or 22. This is usually found on the temple and shows the power of the lenses in “inches”.
This archaic mode of showing lens power is both an interesting detail of past medical science, and a good way to further identify pre-Revolutionary vintage spectacles as belonging to this time.