Though most people today who are aware of pince nez and Oxfords think of them as being solid and fixed in their form, folding pince nez were immensely popular back in the days when these old eyeglass frames represented the cutting edge of both technology and fashion. Several different types of folding mechanisms were devised – and, curiously, the more complex and interesting was considered at the time to be the cheaper and more common of the two.
Pince nez are already highly compact by the standards of both new and old eyeglass frames, reducing the structure to eyerims connected by one of several different varieties of bridge (which will be discussed in detail in future articles). However, the desire to make them even more convenient led to the development of folding varieties (and, in some instances, the appropriate case to carry them).
Regardless of the exact mechanism used to fold the pince nez or Oxfords, the folding process ended with the lenses resting one atop the other, with their flat surfaces touching or nearly so. Thus, the largest dimension of the folding eyewear was reduced to the diameter of one of the eyerims. Probably few more compact vision aids have ever been devised.
Z-fold old eyeglass frames
The most common arrangement invented for pince nez and Oxfords was the z-fold. This is a very intriguing way of folding and unfolding old eyeglass frames, and most surviving examples have such excellent craftsmanship that the action is still crisp, quick, and easy despite the passage of over a hundred years since many of them were first wrought.
Oxfords are best suited to the z-fold, though any spring bridge pince nez (with an arching bridge above the plane of the lenses, connecting them from attachments on the upper curves of eyerims) would also be suitable. It would not be possible to make this exact configuration with vintage eyeglasses that place the bridge between the eyerims rather than above them, such as hoop spring pince nez.
The z-fold bridge is not immovably attached to the eyerims. Instead, each end is attached to one of the eyerims with a single rivet that serves as a pivot. By pulling the inner edge of the righthand lens inwards and towards the right, and pushing the outer edge of the lefthand lens in the same direction, the user snaps the eyerims free of the groove on the underside of the bridge and pivots both lenses so that their convex outer surfaces face towards the left.
This leads to the righthand lens being cupped within the concave interior of the lefthand lens, with the bridge folded diagonally across the top of both.
When opening, the eyerims are pivoted open in opposite directions. Besides a hollowed underside to the ends of the bridge, which snaps into place over the curved top wires of the eyerims, the eyerims themselves contain a tiny, spring-loaded bar which pops out when the glasses are fully opened, extending upwards into a groove in the bridge, thus helping to keep the glasses firmly open. The amount of mechanical miniaturization in these old eyeglass frames makes them a worthwhile purchase even without the intention to wear them – simply as an example of the artistry, skill, and painstaking craftsmanship that went into the making of antique eyeglasses.