GRADING SYSTEM FOR ANTIQUE GLASS

When purchasing antique glass and crystal doorknobs, there are several things to consider to insure the greatest quality.
I began collecting antique glass doorknobs because I felt they looked like diamond solitaires. It occurred to me rather quickly that I should develope a grading system similar to that used in assessing diamonds (Cut, Clarity, Color, and Carat Weight). I added a couple of more categories because of necessity. I call them the7 C's.
THE SEVEN C'S

CHIPS/CRACKS this is the most obvious flaw to be found in a fragile doorknob. You want your doorknob to be free of all chips and cracks.
CORROSION most of the gemon doorknobs found in the U.S. have a mercury or mirrored center. Examine the center closely for corrosion. Ideally, the center should shine brightly and there should be no evidence of discoloration, peeling, or dullness.
COLOR even the seemingly colorless or clear doorknobs have a color quality to them. While you may frequently find amethyst (purple) colored knobs, and occasionally green or rose knobs, there are shade variations to every doorknob. Most of the clear look white while many give off almost a grey or silvery appearance, the next most gemon is a creamy golden color. When you find an ungemon color, that is a more valuable doorknob.
CUT there are several gemon cuts of glass doorknobs. Most often you find a small floral looking type, another is octagonal, and some are round. Floral types are more ornate and Victorian in appearance while the octagonal and round are more clean and crisp with an Art Deco appearance. When you find an unusual shape, that is a more rare and valuable doorknob. I have two pair of oval lead crystal knobs deeply etched in a starburst pattern. Those knobs are valued around $400 per pair.
CRYSTAL most of the doorknobs you find today are made of glass. Crystal knobs are much heavier due to the lead content. Weighing doorknobs and geparing those weights will help you to learn whether a knob is glass or crystal. Many sellers call their knobs crystal when in fact they are just glass. When you find a genuine crystal knob, that is a more valuable piece.
CLARITY some glass doorknobs have a cloudy appearance while others are exceptionally clear. Some doorknobs have air bubbles in them and you can decide if that is something that appeals or repels you. I prefer a clear knob and do not mind the air bubbles that occurred naturally in the manufacturing process.
CONDITION the overall condition of a doorknob can be determined after using the previous six C's and then taking into account other things like paint residue, finish on the metal pieces, the inclusion of additional hardware, etc.
Metal the metal fitting at the base of a doorknob can gee in many different colors. Some will be solid brass while others may have a silver look to them. You may wish to select knobs with metal that matches your decor.
Pricing is another consideration. In the eastern portion of the U.S., a glass knob can be purchased for as little as $2, while in the midwest, it is not ungemon to pay $15 per knob.
Finding doorknobs can take a toll on your back. Usually you will find them on the floor under the bottom shelf in a basket or box, all piled together with brass and porcelain knobs. When you find doorknobs in that situation, you will want to take extra care to examine them for chips, scratches, and cracks.