Sea Glass Lingo: Terms Used by Beach Glass Collectors

 multicolored davenport sea glass

While becoming engrossed in what can truly become a sea glass addiction, you may notice some strange lingo among enthusiasts. On Instagram or Facebook posts, chatter at festivals, and even among the pages of this magazine, you will come upon words that might not be familiar. Whether you are a seasoned collector or just filling your first vase with finds, becoming knowledgeable in the “sea glass lingo” is essential. Below you will find an alphabetical list and a brief definition to help you navigate reading and discussing sea glass.

Beach Glass - Glass that has been naturally tumbled in fresh water such as a lake or river. 

sea pottery blue willow pattern
Blue Willow - A distinctive blue and white pattern on pottery. The tableware that can be found as sea pottery is recognizable by its Chinese landscape and elements. It was first copied and adapted by English pottery artists in the 1700s and is still in production today. If you find a piece of sea pottery and it is blue and white, chances are strong it may fall in the blue willow category. Learn more about Blue Willow History and Lore and Star-Crossed Lovers: The Blue Willow Love Story.

bonfire beach glass
Bonfire Glass - Glass that has been exposed to the high temperature of a fire, usually from burning in a bonfire or as part of trash incineration in a beachside dump. This glass will often have a strange shape and debris, san, ash, or other items lodged inside. Some very special pieces will even have water trapped inside. Learn more about The Journey of Bonfire Glass.

CQ - Shorthand for Craft Quality glass, also referred to as mosaic quality. This quality of glass will be worn enough to be considered sea glass, but may have chips, cracks or rough edges.

Crizzling - This refers to the cracking lines in a piece of sea glass due to exposure to a change in temperatures. Similar to pavement, when cold enough, ice expands and cracks making pot holes. The same damage can also happen to glass.

“C” Shaped Pitting - The result of hydration and also a strong indication of genuine sea glass. “C” marks will form on natural or genuine sea glass; sometimes it is very obvious and other times magnification might be required to see the pitting.

davenport sea glass

Davenport Glass - Sea glass found in Davenport, California. Davenport is well known for its rough surf, extreme glassing, and jaw dropping sea glass. Many of the finds are highly recognizable because of their Lundberg Art Studio origin. Learn more about Beachcombing in Davenport, an interview with Davenport Beachcomber Natalie Brooke, and a Beachcomber's Guide to Santa Cruz, California.

Depression Glass - Depression glass was developed in the earlier part of the 20th century as an affordable alternative to expensive crystal. Makers of Depression glass such as Anchor-Hocking, Federal Glass, Hazel-Atlas, and Lancaster Glass Companies sold their wares at country shops and five-and-dime stores, and they often included free pieces along with household goods such as flour sacks, coffee canisters, and even free with store-bought oatmeal. Depression glass was mass-produced from roughly the 1920s until the 1940s and made in many popular colors.

Flat Lay - A popular artistic expression among collectors to display and photograph their collection in beautiful arrangements. Pieces are laid on a flat surface creating recognizable images or abstract compositions.

Flotsam - The debris from a ship’s cargo which found its way into the water by way of an accident or shipwreck. Learn about the difference between Flotsam and Jetsam.

glaze crazing on beach pottery

Crazing - The spider web like cracking that can form on pottery. This defect is a result of the glaze being stretched too much during the firing process and then contracted during the cooling process. This flaw can appear immediately or years later. In the case of sea pottery, being exposed to harsh temperatures can expedite crazing. Being in conditions where debris can get into the cracks also makes the webbing more obvious.

Flashed and Stained Glass - Sometimes the ingredients to make colored glass were expensive, so glassmakers came up with ways to reproduce the look at a lower cost. Flashed and stained glass were made by combining a thin layer of colored glass or colored enamel paste with a thick layer of clear or white glass. The overall effect mimics solid-colored glass, but the layers are visible from the side.

Hydration - The chemical process a piece of glass endures to become a piece of sea glass. Soda and lime, the main components of glass, are slowly drawn out of the glass because of exposure to the water, leaving behind the well known “pitting.” This process along with natural tumbling is what produces sea glass.

ISGA - The International Sea Glass Association. Established in 2006 with a mission to educate the sea glass community and provide a social outlet for enthusiasts through yearly festivals.

JQ - Shorthand for Jewelry Quality. The opinion of jewelry quality varies from person to person, but in general it is sea glass that is free of shiny spots and has no chips, cracks, or jagged edges. Jewelry-quality glass will also have an overall even frosting.

sea glass bottle kick up

Kick Up - Also called a "punt" or a “push up” is the bottom of many wine bottles. Often found in black, olive, or brown shades of glass. These special pieces are identifiable by their round shape and protruding bump.

Marb - Shorthand for marble. Surely on the “must find list” of any collector. Read more about beach and sea marbles ›

Mermaid Tears - A fun, whimsical name for sea glass or beach glass. Folktales say that sea glass pieces are the tears shed by mermaids when a sailor drowns.

Milk Glass - Opaque and translucent milk glass also known as opal glass, milk glass is made by adding tin, zinc oxide, fluorides, phosphates, arsenic, antimony, or calcium in the form of bone ash (which creates a translucent opaline glass). Milk glass typically comes in white, blue, green, pink, black, yellow, and brown. Some milk glass was made with manganese dioxide to keep it bright white, and this compound reacts to sunlight over time turning the milk glass a light lavender. Pigmented structural glass, a type of strong opaque glass known as vitrolite, was used in opaque colored tiles, counters, tables, and more. Custard glass is a variant of milk glass with a subtle yellow shade reminiscent of pudding or custard. Custard glass was made by adding uranium oxide during manufacture, and the resulting ultraviolet glass fluoresces under long-wave black light. Milk glass was first made in Venice in the 15th or 16th century and became very popular beginning in the 1880s as a less-expensive substitute for porcelain. By the early 20th century, it was a status symbol, and early pieces of opal glass are highly collectible today. Read more about milk glass.

seaham multis sea glass

Multi - Commonly from Seaham, England, and Davenport, California, this sea glass is recognizable through the multiple colors that are apparent in the pieces. Hartley Wood and Company made colorful swirled glass vases and glassware in Sunderland, England, and the multicolored glass found on beaches of the local coast may come from the discarded remnants of this glass. In Davenport, California, Lundberg Studio glass artists produced exotic-colored vases, bottles, paperweights, and more. Discarded pieces have ended up back on the beach, tumbled into smooth multicolored nuggets by the huge surf. Multicolor pieces can be found on beaches around the world, perhaps from cast-off pieces of art glass, stained glass, and even bonfire glass. From one color and clear, to a rainbow of colors in each shard, they are truly a lucky find. Read more about beachcombing in Seaham and beachcombing in Davenport.

Oiling Glass - Occasionally when pieces of glass are thoroughly tumbled by waves, they have such a frosted look that it is difficult to see the actual color of the glass. Using a small amount of mineral oil on the surface can bring out the color once again. This is more commonly done on jewelry to enhance the piece, but can be removed with soap and water.

Opalescent GlassOpalescent glass is translucent and casts an orange shadow or appears orange along thin edges, due to fine particles suspended in the glass and scattered by the light. In the early 20th century, it was used in decorative glassware, and early pieces of opal glass are highly collectible today.

Opaque or Translucent Glass - Originally made in 15th-century Venice, opaque and translucent glass were made by adding tin, zinc oxide, fluorides, phosphates, arsenic, antimony, or calcium during manufacture. In addition to white “milk glass,” this glass was made a rainbow of colors. Light yellow “custard” glass was made with uranium oxide, which fluoresces in black light. Costume jewelry, dishware, cosmetic jars, and decorative opaque and translucent glassware were popular from the late 19th century through the first half of the 20th century.

Patina - Normally a word used to describe the surface of the glass. The amount of pitting, the smoothness, or overall surface can be explained as the patina on the glass.

Pirate Glass - Sea glass that is so dark it appears black is often called “pirate glass” though it probably had nothing to do with actual pirates. This black sea glass is often from very old antique bottles that had a high iron content in order to stop sunlight from reaching — and spoiling — the contents. The West Indies is known as a treasure trove of black sea glass, and there were real pirates from the River Thames.

Sea Glass - Glass that has been naturally tumbled in salt water.

Sea Pottery - Pottery shards from tiles, vessels, and more that were naturally worn by the waves.

beach pottery tiles

Sea Tiles - Wave-worn tiles mostly found in square shapes, but octagons and triangles and many other shapes are also possible to find. These sea tile pieces are identifiable by their shape and color or pattern on one side and a sandy porcelain texture sometimes with grooves to hold the mortar on the opposite side.

Seeding - The controversial practice of purposefully putting broken glass by a shoreline to increase the quantity of glass to be found in the future. This is also commonly done with sought-after colors and pieces such as marbles. Read more about Seeding the Beaches

Slag Glass - There are two types of slag glass. The first type of slag glass is also known as “Malachite” or “Marble” glass and is opaque white glass purposely mixed with a variety of glass colors to create a marbleized look. It was made by several British companies and a few French companies in the 1880s and 1890s, and it is still manufactured in the U.S.

The second type of slag glass is a byproduct of an industrial process. Leland Blue Stone was created by iron smelting by the Leland Lake Superior Iron Company in Michigan in the late 1800s. Similarly, Frankfort Green came from the Frankfort Iron Works in Elberta, Michigan. Pieces of blue and green waste glass can also be found along the northeast coast of England, sometimes known as "dragon glass."

Stack - The art and practice of stacking sea glass shards into cairns. For competition or just a fun photo composition, seeing how high you can go is surely a good way to play with your finds. Just be sure they will land on something soft when they fall. Read more about stacks of rocks and more in The History of Cairns.

beach glass stopper

Stopper - A special find for any collector, stoppers are the “T” shaped circular pieces that usually originate from antique bottles, decanters, and vials. Many variations of shapes and sizes can be found. Read A Brief History of Glass Stoppers, and see some beautiful stopper collections in Beachcombing Showstoppers and They Just Kept Coming

River Glass - Beach glass that has been smoothed by the flow of river waters. Often found to be much more smooth and silky to the touch than sea or beach glass.

Rust Glass - Although you might be excited to find a faint yellow or orange piece of glass, be sure it is not an imposter. In areas with metal debris in the water, it can be common for the rust from those objects to affect the water and glass. Pieces will appear colored when they are in fact just stained by decades of exposure to rust.

Throwback - When a piece of glass is not quite worn enough to keep. As long as it is not sharp enough to endanger someone, throw it back with hopes that one day it will wash up once again. As you become a seasoned collector your opinion of a “throwback” tends to change.

Tumbled Glass - Broken glass that has been smoothed by tumbling in a rock tumbler or similar device until it resembles natural sea or beach glass. Tumbled glass typically lacks the "C" marks and patina caused by the waves and instead have a satiny-smooth finish. Sometimes called "cultured" glass, these pieces are sometimes passed off as real sea glass. Read more about the difference between real and fake sea glass and 5 tips to tell real sea glass from fake sea glass.

UV - Ultraviolet glass also called uranium glass, canary glass, or Vaseline glass. When a collector describes a piece of glass as being UV, they are referring to its quality of glowing when exposed to black light or ultraviolet light. The glass has small traces of uranium or other minerals in the glass mixture causing this unexpected reaction. This glass was mainly produced for tableware and household items from around 1840 up until World War II. The uranium in canary glass gives the glass its bright-green color in natural light, and causes the glass to glow vivid neon green under a black light. Learn more about Ultraviolet Sea Glass.

Wrack - The highest point where the high tide will carry debris. It is usually where you will find a line of seaweed left behind and, if you are lucky, some hidden treasures.

The list could go on and on. Some of these definitions might be slightly different depending on the opinion of each collector, but this will give you a go-to list when you see or hear a word that’s not familiar. Since these are brief definitions, it would be fun to continue on your own and research them further. You will find a wealth of knowledge, if you look into some of the many sea glass books that are available. Hope you now have a good grasp on the sea glass lingo!

Learn more about where your beach glass comes from in Glassification: Categorizing Sea Glass. 

Feel free to add your terms in the comments!

Watch videos about all the colors of sea and beach glass

Learn more about sea and beach glass colors:

where does sea glass get its color

This article appeared in the Glassing Magazine September 2017 issue and has been updated since then with new terms.


I’ve lived in Santa Cruz my entire life & never made it to Davenport beach to beach-comb. I literally live just a few miles away. It’s pretty darn hard to get to.

Katharyn Crocker April 01, 2023

I collect glass from beaches between Glenelg and Grange in South Australia. Our sand is very fine so the glass seems to wear differently to glass found in America or Europe. ?

Greg Peters August 29, 2022

Does anyone know a less used synonym/slang for washed up glass on the Lake Erie shore…Mom has been gone 28 yrs and I have forgotten her word for " let’s go collect “___ _____”:(

Lynn Tomczak August 24, 2022

what about Georgian safety glass it has pieces of wire inside usually in the shape of triangles sometimes a cross or letter. ?

Roy August 02, 2021

“Politicians, old buildings and prostitutes become respectable with age”
Mark Twain

Seems the same is true for trash

John February 11, 2021

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