Sea Glass Hunt: The Good Kind of Blues

The story behind one of many beachcombers' favorite shades of sea glass

Sea glass might have man-made origins, but it’s the ocean — the ceaseless beat of waves and corrosive and erosive natures of salt and sand — that renders shards lovely. That’s my justification, anyway, for tackling the subject in what’s primarily a nature column.

The lovely litter can be found in all kinds of colors. We’ll just focus on one popular color today, cobalt blue, and leave the rest of the rainbow for another day. 

What it looks like:

Cobalt blue glass is that deep, intense, royal blue shade that stands out strikingly among pieces of other, gentler hues. The color comes from cobalt oxide, an additive glassmakers love because its high melting point means it’s hard to disrupt the compound when melting and re-melting glass. That makes for consistent coloration from batch to batch.

But cobalt oxide has always been pricey. As Richard LaMotte, the authoritative voice on collecting, points out in his splendid book "Pure Sea Glass," the additive’s cost meant that it wasn’t often used to make beverage bottles, which were big and needed to be made in large quantities.

Instead, cobalt glass was usually reserved for medicine bottles — think Milk of Magnesia, Bromo-Seltzer and Vick’s VapoRub — and as a result, they were usually tossed away near homes as opposed to dumped offshore. 

That means it’s not as common as other sea glass colors. While a piece of cobalt blue glass is not nearly as rare as a ruby red shard or a yellow one, it's still something of a prize.

Similar to cobalt blue is the slightly paler cornflower blue, made with smaller amounts of cobalt oxide. It is to cobalt blue what pink is to red: a softer, gentler version of the same color. It’s more rare than cobalt, and a fun find.

Where to find it:

New Jersey collectors have long scoured the Shore for sea-worn glass. Until recently, Long Beach Island was a reliable place to find it by the pocketful, but there, as elsewhere, amounts have dwindled. 

That’s partly because of the rise of plastics over the last half-century, and because ocean dumping is far less common than it used to be. The latter is a good thing, certainly, but it means that even as more beachcombers develop an interest in sea glass collecting, there’s less glass out there for the picking.

Still, if you know where and how to look, you’ll likely come home with a few pieces.

If you can hit a low tide following a winter storm, you’ll have the most luck. And avoid scouring recently replenished beaches.

Why bother:

Nobody needs to tell a confirmed sea glass lover why collecting the beautiful little gems is fun. Finding former trash transformed into such a pretty thing can be a joy, and there’s something to be said for the thrill of the hunt.

Looking closely at the glass you find can give you a new appreciation of it, and tell you something of its history. 

Does your cobalt piece have ridges on a gentle, outside curve? It’s likely it came from the mouth of a screw-top medicine bottle. 

Does it have an all-over pattern of raised bumps or lines? Many old poison bottles came in cobalt blue, and were stamped with such distinctive patterns to make them easy to tell apart from other products, even in the dark. 

There’s a story in every shard!


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