What is Black Sea Glass?
We get asked this question a lot. The term "Black Glass" is used because without a strong light source, the glass looks black. On a pebble beach, like Seaham Beach in England, it is almost impossible to tell the difference between black rocks and black sea glass.
We got pretty good at telling the difference and could pick out the glass most of the time. You sometimes can't even see the color when holding it up to the sun.
The best thing to use is the light on a mobile phone. We carried ours with us and used the flashlight on the phone to hold up to the glass. In some cases it was too bright outside and we almost missed one of the finest pieces I ever found. It is a dark blue at the tip, swirling down to a deep purple. But the sun was so bright outside, I almost missed the blue tip.
Black glass was generally used to protect contents which could be degraded by light. It's thickness and color prevented light from entering the bottle and deteriorating the liquid inside.
On Seaham Beach, the old glass bottle factory used a variety of colors in it's "Black Glass", so you never know what color it will be when you find it. That glass dates from around 1850 - 1925 when the factory closed.
The black glass that we found on the Mediterranean Coast of Spain was older, more like 200-400 years old because is was typically used on old sailing ships.
Another kind of "Black Sea Glass" is called Vitrite. Vitrite is a kind of "slag glass" and was primarily used as a dielectric, or electrical insulator, generally found in the base of common incandescent light bulbs. General Electric was one of the largest producers of these incandescent bulbs along the shores of Lake Erie in Ohio. The more lumpy shapes are usually the glass slag that comes from the furnaces of the light bulb manufacturing facilities. Sea glass hunters still do find some discarded shards in that area.
The term "slag glass" also refers to a type of decorative glass primarily used in the 19th century to create beautiful marbled pieces designed to resemble malachite or other striped stones.
Black sea glass is very rare and it's even more rare when you find a color other than the typical amber/olive. Browse our collection of black glass and see red, burgundy, blue, purple, orange and gray.