DIY Smoothing of Chip in Wine Glass
from https://www.artistry-in-glass.com/

If you have very fine and expensve glassware, it is best to send chipped glasses to a professional crystal repair service. Because these repair services grind the entire top of the glass down, you may notice they are microscopically shorter than their unrepaired mates, but on a set table, you couldn't detect a difference.

You can opt to smooth out chips on your own, but the repair will be noticeable, depending on the size of the repair.

Using Diamond Files

The cost of industrial diamonds has plummeted over the last 10 years and diamond files are a very affordable way to grind and smooth glass. This is because diamond, with a hardness of 10, is much much harder than glass (hardness 6 for glass and 5 for lead crystal).

Diamond file for smoothing chips File (available on Amazon) advertised specifically for glass has 200 grit diamonds embedded in a carbide steel rod that has a rounded and a flat side for versatile smoothing. We feel that if you are going to the trouble of buying diamond files you will be better off purchasing the selection that comes in three grit sizes – 140#, 200#, and 400#. This set of files allows you to remove sharp edges with a coarse file then finish with a finer (400 grit) file.

Using Sandpaper instead of Diamond Files

If you would rather not bother to order diamond files from Amazon, wet and dry sandpaper from your local hardware store will do the job just as well. Wrapping the sandpaper around a pencil provides an easy way to smooth chips. Depending on the size of the chip, start with a coarse (#100) grit and work down through the grits to fine (#400) or even superfine (#1200). The benefit of sandpaper is that, by using a fine grit, you can achieve a finer polish than with a diamond file. The disadvantage is that silicon carbide is not as abrasive as diamond (Moh’s hardness =9 compared to 10 for diamond). So for big chips in hard glass, a diamond file will be faster.

Wet Dry sandpaper is made of silicon carbide grit embedded in a durable substrate. Choose the selection of 320 thru 10,000 grits to permit smoothing and fine polishing of the chip.

Chips in the foot of a wine glass

There is no perfect way to fix a cracked foot but the out-of-round base is acceptable to many customers as a way of salvaging a valuable crystal wine glass.

Cut Crystal

Chips in the crenulated rims of American Cut Crystal are a very common type of damage The best solution is to smooth off the sharp edges by hand using diamond files recommend in this article.

Cracks in crystal and glassware

Cracks in crystal rims are hard or impossible to repair: Sometimes a chip in the rim is associated with a crack. Normal polishing methods, on a mechanical lap, create vibrations that make the crack “run” (extend downwards).