Sea glass and beach glass are pieces of glass, pottery, and tableware that has been weathered by water until it is smooth and frosted. Sea glass comes from the ocean and gets its characteristic appearance from mechanical weathering by waves and chemical weathering by seawater. Beach glass comes from lakes and rivers. Beach glass typically retains more of its original color, is sharper than sea glass, and appears less-frosted. It takes at least 20 to 40 years to form sea glass and beach glass. Some types of sea glass are hundreds of years old.
Sea Glass Colors
Sea glass colors depend on the original color and chemistry of the glass, as well as the interaction between chemicals in water and the glass. Most sea glass comes from broken bottles, so it is clear, white, brown, or kelly green. Green, brown and clear glass mostly comes from beer bottles, wine bottles, and other beverage containers. White and clear glass come from windows, windshields, glasses, and other sources. However, there are rare colors, which are more valuable.
- Kelly green:
- Amber: Whiskey, other spirits, old bleach bottles, medicine bottles
- Amberina (golden amber): Spirit bottles
- Lime green
- Forest green
- Ice Blue
- Other greens: mid-1900s Coca-Cola, RC Cola, Dr Pepper, beer bottles, ink bottles, baking soda bottles
- Opaque white: Milk bottles
- Cobalt and cornflower blue: Vicks VapoRub, Bromo-Seltzer, Milk of Magnesia, poison bottles
- Aqua: Ball Mason jars, 19th century glass bottles
- Pink: Plates from the Great Depression
- Teal: Mateus wine bottles
- Black: Often 18th century wine, beer, gin
- Yellow: 1930s Vaseline
- Turquoise: Art glass, tableware
- Red: Car tail lights, Schlitz bottles, nautical lights
- Orange: Very rare, only about one in every 10,000 pieces of sea glass
Some of the oldest sea glass is black sea glass, which may date back to the 15th century. The black color comes from iron added to the glass to increase its strength. Oxidation from sea water and exposure to ultraviolet light darkens the glass over time. If you look closely under bright light, this glass is usually a dark green or brown.
Where to Find Sea Glass and Beach Glass
Theoretically, sea glass and beach glass occur near any body of water. However, currents deposit glass more in some locations than others. Some of the best sea glass beaches are:
- Northeastern Atlantic coast of the United States
- Port Angeles and Port Townsend, Washington on the West Coast
- Glass Beach, Fort Bragg, California
- Isle of Man
- Northeast and northwest England
- Puerto Rico
- Nova Scotia
- Southern Spain
- Dominican Republic
The best time for finding sea glass is at the first low tide following a storm or during the spring tides (perigean and proxigean tides).
Beach glass occurs around lakes and rivers. The areas around the Great Lakes and the inland waterways of Chesapeake Bay and Puget Sound are great starting points.
Be aware, some places have laws that prohibit the collection of sea glass and beach glass. For example, the Coastal Protection Act 1949 in the UK prohibits collection of shells, pebbles, and sea glass. Breaking this law carries a fine of up to £1,000. Hawaii also has laws against collecting shells, rocks, sand, and glass. Whether or not you’ll actually get fined for taking souvenirs depends on the locality.
How to Spot Fake Sea Glass
A lot of products labeled as “sea glass” are just tumbled glass. While there is nothing wrong with tumbled glass, make certain you aren’t paying sea glass prices for it! Genuine sea glass has tiny c-shaped marks made by the back-and-forth action of tides. The indentations are visible under magnification.
Beach glass may or may not have these marks. Beach glass on the shore of a large lake probably will bear marks, but river-tumbled glass may not. Also, be aware there is tumbled genuine sea/beach glass. This is sea glass that bore some sort of defect, so a seller put it into a tumbler to improve its appearance. This treatment lowers the value of the glass.
How to Make Sea Glass in a Tumbler
Tumbled glass looks much like real sea glass and it’s great for jewelry and crafts. Tumbled glass is also known as manmade sea glass or artificial sea glass. While tumbling glass takes a lot less time than waiting for nature, the resulting glass lacks the history of the real deal. It’s still pretty, so if you want to make some, grab a rock tumbler and get started:
- Rock tumbler
- Broken glass (~ 2 lbs or 32 oz)
- Sand or grit (~ 2 tablespoons or 25 grams)
- Sea water, synthetic sea water, or regular water
- Baking soda (sodium bicarbonate) – optional
First, start with broken glass. Good options for recycling glass include wine bottles, vintage ashtrays and vases, whiskey bottles, Perrier bottles (green), Prosecco bottles (blue). Protect your hands with gloves if you must handle the glass. If you must break glass, place it inside a paper bag, cover the bag with a towel, and strike the bag with a hammer.
Tumbling smooths the sharp edges, resulting in glass chunks that are small than the original pieces. Also, the longer you tumble the glass, the rounder and smaller the pieces becomes. Aim for a collection of broken glass shards that are all approximately the same size. Choose pieces that are at least 1/4 inch (0.6 cm) thick. It’s okay if there are some small bits, but realize they probably won’t survive the process.
Nature tumbles glass using sand. But, you can use any coarse grit, such as ceramic pellets or silicon carbide.
- Add broken glass so that the tumbler barrel is 2/3 full.
- Add 2 tablespoons or 25 grams of sand or grit.
- Pour in water or sea water. You don’t want to overfill the barrel, so start with just enough that it’s visible through the glass. Alternatively, follow the instructions accompanying the rock tumbler.
- Some types of glass release gases. Add 1/4 tablespoon (3.6 grams) of baking soda to neutralize some of these chemicals.
- Tumble, tumble, tumble. The process takes around 4-5 days. But, check the tumbler periodically and make certain it is not bulging outward from gas pressure buildup.
- If you like, run the tumbler longer, but check it every day.
- Rinse off the tumbled glass with water. This glass has the classic frosted appearance of sea glass. If you want shiny, polished glass, run the tumbler again using aluminum oxide (or another fine grit) in place of the sand or coarse grit.
How to Make Sea Glass Without a Tumbler
Some websites claim you can make sea glass without a tumbler simply by agitating pieces of glass, sand, and water in a jar. The only possible way of this working is if you put the jar in your washer or dryer on infinite spin (definitely not recommended).
However, making sea glass without a rock tumbler works fine if you use a cement mixer. The advantage of this method is that you can make a lot of manmade sea glass very quickly.
- Cement mixer
- 1-2 kilograms of glass
- 5 liters of water
- ~ 1/2 kilogram or 1 pound of play sand or beach sand
- Put the glass, water, and sand in the cement mixer.
- Run the machine for about 4 hours. Check on the glass.
- If necessary, run the mixer another 2 to 4 hours.
- Ideally, rinse the glass outdoors using a strainer or colander, bucket, and garden hose. Don’t use a sink because the sank clogs pipes.
- Enjoy your sea glass.
- La Motte, R. (2009). Pure Sea Glass. Sea Glass Publishing. ISBN 978-0975324608.
- Park, Elizabeth. “Where Does Beach Glass Come From?”. USA Today.
- Wyman, Josephine. Photographic Exploration of Sea Glass.