We see a lot of glass door knobs here at the Hippo Hardware. Not only in terms of style, but age as well. Glass doorknobs were produced widely for over 50 years! Although the glass part of the knob is the flash and style, a big trick to dating them is in the metal base. The subtle design choices can tell you the difference between a 1900 door knob and a 1940's doorknob. These can then tell you are sorts of useful things like "Are these original to my house?" or "are these knobs are from the same set?".
Below is a brief walk through by era:
1890's - The Originals
These were super rare and cutting edge at the time. We like to throw around the term 'mansion-ware' here for stuff like this - only owned by the very wealthy of the time (thus not a lot made). Some glass hardware already existed, notably cabinet knobs, but nothing in the way of door knobs. These knobs feature a very wide base with steps up to the glass. The knobs are frequently if not exclusively pinned (not like your girl in the 1950's but like a brass nail running through the base to attach the knob to the spindle). This has the plus side of being very secure and the downside of being very hard to remove. These knobs are most easily distinguished by their base. The glass came in hexagonal, round, and even some more unusual shapes such as egg shaped or faceted spheres.
Octagonal glass doorknob with wide, stepped base. Pin secures knob to the spindle.
1900's - The Up and Coming
Here we see glass knobs become a little more mainstream but still not much outside of the upper class. This era, again not widely produced, features the more narrow (and familiar) base like but maintains the straight shaft (meaning not threaded, as will become very common later). An easy way to note these knobs is the narrow base without threads (requiring a user to screw directly into the spindle instead of threading a screw through the base). These door knobs also came in a wide variety of glass shapes, although what we see most often are octagonal, shown here.
Octagonal glass slip on door knob
1910's - Breaking into the Mainstream
The first twist-on door knob came out right about 1915, give or take a few years. The twist on style revolutionized all door knobs at the time, glass and otherwise. Instead of needing lots of tiny washers to get your knobs the correct width apart for your door, you could just screw down your knob and tighten the set screw - Voila! Modern magic. These first glass twist-on door knobs feature the same heavy cast brass bases, but instead of a smooth square, are round and threaded inside. See below for a great example: a twist on glass egg doorknob, a fantastic carved glass octagonal doorknob, and a very unusual hollow glass knob filled with mercury. Some additional clues here are the convex style (rounded top instead of a cut face) tend to be from this era.
Carved octagonal glass knob
Mercury glass doorknob with a twist-on base
1920's - Everybody Loves Me
It was really the 1920's that saw glass door knobs in a huge percentage of homes. They became affordable and accessible and boy did those homeowners love 'em. Here we see the twist on style base with the with the heavy cast brass but the glass is generally a more standardized shape - octagonal with a cut face or fluted.
Although they weren't common, Schlage patented and produced the first integrated knobset in the mid-1920's. These were new technology at the time and took another 30 years to really catch on.
At hippo, this is generally the beginning of where our stock goes from the specialty case to the beautifully mounded bins. A lot of the really great novelty colors (green, amber, blue), such as these great black glass knobs, were produced in this era.
1920's black glass octagonal doorknob
1930's - Keep On Keeping On
Glass doorknobs continued to be wildly popular, so much so that we really see the 'budget' versions getting big. Fluted style really overtakes the octagonal in popularity in the 1930's but both are still widely used. Although we don't have an exact date on when they started, something called 'contractor grade' aka 'super cheap' becomes much more common.
Additionally, as they become more wide spread, bases tend to move from cast brass to stamped brass over iron (like these guys - a fluted glass doorknob with a stamped brass base) or sometimes even stamped steel over iron. Additionally, this is really when we see all those unusual, creative glass shapes all but disappear. There were still outliers, but they become rare. Glass knobs had become more common in less affluent homes although were generally a step up from the plain steel knobs generally seen in working class homes of the time.
1940's - The Wave Has Crested
We finally start to see a small decline in glass knobs - octagonal fading much more quickly than fluted. Although they're still widely produced, they are beginning to lose their grip. Here we also get to see the beginning of the shift of the type of doorknobs you'd find at a new hardware store - the large drill outs and integrated latch. These knobs were produced in the 1940's through the early 1950's. We also see what we affectionately think of as the 'squashed' glass knob made by Dexter - a slightly squatter version of the fluted and round glass knob.
1950's - Time to Move On
Glass doorknobs were really on their way out by this point, having completed the cycle of rare elite to mass consumption to out of style.
1960s to Now - Reproductions
That certainly doesn't mean glass knobs weren't still made. Now, instead, the focus was on reproductions or restoration. Anything with a pot metal or ZMAC base is certainly in this category (such as these fluted glass knobs). Also a set screw with anything other than a slotted head screw is another dead giveway as a production. There are also higher end reproductions with cast brass bases (such as these octagonal glass reproductions here)
Reproduction fluted glass doorknobs
Reproduction octagonal glass doorknobs
Share any tips or tricks you may have in caring for, restoring, or replacing your glass doorknobs in the comments!