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Home - Sea Glass Directory - Sea Glass Guide

Black Sea Glass, Black Beach Glass

On this page, you'll find out about:

From what we've researched, heard from others, and found through experience is that true "black" glass is almost impossible to find.

Well, not impossible. Just very hard. We'll talk about why farther down the page.

What Is Black Sea Glass?

The term "black glass" (also called blackglass), as used frequently by sea glass collectors as well as collectors of bottles, insulators and some other old glass products, often refers to glass that APPEARS to be black.

Here's an example of some "black sea glass" from Italy.

Black sea glass - dark olive from Italy
Black sea glass - dark olive from Italy
"Black" Sea Glass from Italy actually is a Very Dark Olive

The common name "black glass" is perfectly fine to use when referring to glass that appears to be black to the naked eye.

This very dark glass, though, when held to bright light, shows that it is actually colored.

Black sea glass - dark olive from Italy

This sea glass from Italy appears black until held up to bright light, as Lin is doing here.

"Black glass" in many cases is a very dark olive green. However, it can also be a very dark shade of purple, red, blue, or brown..

In the next photos, the "black sea glass" is a somewhat lighter shade of green, which can be seen when the sun shines through it.

Black sea glass - dark olive from Italy
Black sea glass - dark olive from Italy

In normal lighting, this piece would be considered "black glass," while it's actually a dark shade of green.

Black Sea Glass - Rare?

"Black glass" of dark green or dark brown were in fairly common use for bottles, although even these colors are somewhat rare to find in a sea glass collection. Why?

Well, for one very good reason at least - it's very difficult in normal lighting to tell the difference between a piece of very dark, frosted sea glass and the pebbles or rocks on the beach. Add some seaweed and shells and your eyes are going to have a a lot of fun trying to pick it out.

***  When we have found black glass, it has NOT been because of the color; rather, it, just "looked" like sea glass.
After searching for sea glass on many trips to the beach, your eye begins to catch not only colors and shapes but will start to catch the type of frosted or pitted surface found almost exclusively on sea or beach glass.
So, in spite of being the same color as everything around it, your trained eye may still "fixate" on that object.

Much of the "black glass," or very dark glass, that ends up as tumbled, frosted sea glass was originally from bottles containing fluids that could be damaged by exposure to sunlight. This was most important one hundred years ago before refrigeration existed and before the "sophisticated" preservatives that are now widely used.

In many cases medicines and chemicals or even beer and wine had to be transported and stored for long periods of time in less than optimum conditions, and dark, thick glass was one of the best ways to insure conservation of the liquid the bottles contained.

Summarizing this information, then, we can say that black beach/sea glass is fairly rare among collectors for at least these two reasons.

  • First, it is extremely hard to distinguish a tumbled black glass fragment from the other rocks on the beach, so what little there might be is likely to be overlooked.
  • Second, most black glass bottles were made before 1880. Other black glass products (see below) make up only a tiny portion of production compared to bottles..

More About the Use of Black Glass in Bottles

Strength - Most of the black glass bottles were made by adding iron slag, which produced a stronger glass more resistant to shattering; another reason for using black glass for bottles subject to harsh conditions in centuries past.

You might compare the strength of this "fortified" glass to some other glass colors. Colors such as blue, green, brown, and red were generally made by adding metals or combinations of metals. The strength of the glass was affected by how the metal used reacted with the other ingredients in the glass-making process.

From what we've seen, the very dark "black" sea glass is more resistant to breakage, and very dark colors (with the added iron slag, etc) result in finds of some pretty hunky old sea glass.

The Making of Black Glass for Black Glass Merchandise

The center for glassmaking from the 14th century was the island of Murano in present-day Italy, where many new techniques were developed. 

Murano became the center of a lucrative export trade in dinnerware, mirrors, and other luxury items.  Black glass was called obsidianus after obsidian stone.
Milk glass first made in Venice in the 16th century included black glass.
Influenced by the milk glass from Venice, Opaline glass was a decorative style of glass made in France from 1800 to the 1890s and colors included black glass.
Some Depression glass was black.  This was dinnerware and related glassware, not bottles. For example, this flower arrangement bowl.
Black depression glass flower bowl

Photo courtesy of
Black depression glass flower bowl.
See Warman's Depression Glass: Identification and Value Guide
Contemporary Fiesta ware (since 1986) included black glass.
Other general uses:
Vitrite (scroll down for more information), also known as foam glass, is a very low fusing point black glass mainly used for the insulation base of electric lamps.  
Other agents used to produce "black" glass are: Chromium, a powerful coloring agent used to produce dark green to black glass, now replacing the iron oxide used previously. Sulfur with iron and carbon produces amber glass which can vary from very light straw to a deep reddish-brown or even black.


Kelly Johnson, one of our viewers, has done research on vitrite and has kindly add this information:

Vitrite is slag glass that was used a dielectric which is an electrical insulator that was used at the base of incandescent light bulbs some 65-75 years ago. 

If you break a thin piece of this and hold it up to the light you will see dark purple/blue glass, some look black on the ground and is passed up. 

This glass was made up of ground-up glass along with lead and manganese oxide (the manganese gives it the dark purple color). 

General Electric produced incandescent light bulbs in Conneaut, Ohio along Lake Erie between 1941 and 2008. (see fig. 10) From 1950 – 1960’s its rumored GE would discard glass and it was used as landfill along the shoreline.

Here is black glass from Lake Erie (I did a college paper on Sea/Beach Glass and wouldn't you know it, could not find any of this glass for my presentation this Spring, but 2 weeks we go on vacation and I found some.) 

vitrite slag black sea glass

Next, find out about these exciting sea glass colors:

Blue Sea Glass
Blue Sea Glass
See beautiful blue sea glass photos. What are the different blues that are found in beach glass colors? Blue shards of beach glass come in many hues and intensities...

Green Sea Glass
Green Sea Glass
It looks so minty, but tastes salty. In the right light, green sea glass is prettier than an emerald. What is it? Green sea or beach glass began as discarded bottles or ...

Yellow Sea Glass
Yellow and Orange Sea Glass Colors
Among the rarest colors, yellow and orange sea glass is highly prized by sea glass collectors and artists.

Sea Glass
Red Sea Glass is a Rare Beach Find
Why is it hard to find? How can I find it? Here, we will focus on finding rare beach glass - why certain beaches have the ...

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