The physical action of sea water and sand particles on glass produces the phenomenon termed Sea Glass.
The constant movement of sand caused by the action of water creates an abrasive action similar to sandpaper. The coarser the grain of sand the more abrasive is the action and more aggressive the movement of the water, the more abrasive action the sand has on the surface of the glass.
The result of this on sea glass differs to that found on Beach Glass, found on the shores around fresh water lakes.
Both are frosted in appearance with Sea Glass etching being deeper and more defined than that of Beach Glass.
The reason for this happening is because seawater has a different PH level (acidity level balance) to fresh water and therefore etches the glass differently because of the physical reactions.
The glass fragments are rounded by the action of the water with the sharp edges being smoothed down.
These uniquely formed treasures can sometimes be found to have C shaped cracks/marks in them. How is sea glass made is due to the fact that the Sodium, Na, in the glass is replaced by Hydrogen ions, H+ from the water and the resultant Sodium Hydroxide, NaOH, is leached from the surface leaving it frosted.
2Na +2H2O= 2NaOH + H2↑
20 to 30 years later, these weathered shards or pieces of sea glass have found their way to the shoreline of beaches around the world. Some shards of sea glass have been found that date back to over a 100 years ago! The art of sea glass identification can be quite addictive once you start examining your own collections. That and a tad frustrating at times if you have no marks or shape to go by.
A) For sea glass to actually arrive on a beach it has to come from somewhere. There has to be some kind of human involvement. As it is today, ships travel the sea lanes constantly and in days gone by they didn't stand up to the mercy of storms as well as the modern ships of today. Ships were often dashed against the coastline rocks and their cargoes broken apart to eventually be deposited on the shoreline.
This included bottles of 'grog', china, glassware, tableware, pottery and crockery - broken, antique dated pieces now found on modern beaches throughout the world.
B) It's not exactly something to be proud of but up until the mid 50's and possibly later, we tended to use the sea as a natural dumping ground...a tip for unwanted refuge including glass, china electrical components etc.
These pieces of trash are being constantly worked on by sea and sand and broken down. Some pieces eventually find their way back to the landmass as sea glass, sea pottery and scrap metal pieces as well as, sadly, modern day plastic.
Sea Glass loves a good storm and so do we, collectors of the treasures. With storms come winds and huge waves creating massive sand tumbling and more abrasive action. Sea Glass once buried beneath the sand can be suddenly 'dug up' and tumbled onto the shoreline to be collected by some lucky collector.
A strong off shore wind is excellent as well, as this churns the waves and creates a digging action that can only result in some hidden treasures reaching the surface.
Constant wave action helps the sand act like sandpaper, scratching away at the surface of the glass and smoothing its edges even more.
The constant ebb and flo of the sea water pushes the sea glass to the shore and sometimes these pieces get wedged between rocks. A great place to discover that illusive piece of glass history. When out collecting sea glass, always look under rocks, you never know what you will find.
You can always tell the difference between a piece of genuine sea glass to that of a fake as its surface is well frosted, almost powdery and there are usually 'C' shaped marks or groves on its surface
Choose a low tide and a day after a storm, preferably a week day when other collectors are not down there hunting for treasure. Enjoy the experience of the 'hunt' and have fun sorting out your well earned collection.