Discover the Allure of Blue Sea Glass: A Treasure from the Ocean's Depths

February 27, 2024

By OceanFinds

The allure of blue sea glass, with its captivating shades like cobalt, cornflower, and the gentle hues of soft blue, captures the imagination of beachcombers and collectors alike. Distinct from the greens of seafoam or the aqua spectrum, true blue sea glass is a treasured find, celebrated for its rarity and beauty. The brilliance of cobalt blue sea glass comes from the mineral cobalt oxide, a favored colorant in glassmaking that has been used for centuries to create bottles and items with a deep, consistent blue.

Blue Seaglass

Video courtesy of Beachcombing Magazine. Source here.

The Enigmatic Beauty of Blue Sea Glass

Blue sea glass begins as fragments of glass discarded into the ocean. Over decades, these pieces undergo a remarkable transformation, weathered by saltwater and tumbled by waves, resulting in smooth, frosted gems scattered along the coastline. The allure of blue sea glass lies not just in its beauty, but in its story – a journey of rebirth and redemption from pollution to a piece of natural art.

The Rarity of Blue Sea Glass

Among the spectrum of sea glass colors, blue holds a place of distinction due to its scarcity and the enchantment it carries. The rarity of blue sea glass is a reflection of its source materials, which were less commonly produced and discarded. Cobalt blue, for instance, originates from medicinal bottles, poison containers, and seltzer water bottles from the early 20th century. Lighter shades, such as aqua or soft blue, often come from Mason jars, ink bottles, and windows from older homes. The scarcity of these original items makes finding a piece of blue sea glass a delightful surprise for collectors, akin to discovering a precious gem.


The Origins of Coblat (Dark) Glass

The fascination with cobalt blue glass isn’t new; it dates back to ancient civilizations. The Egyptians and Mesopotamians were among the first to showcase their love for this vibrant color, embedding cobalt glass in King Tut’s gold death mask and adorning the elite with cobalt blue beads, evidence of its luxury status millennia ago.

By the late 1700s, cobalt blue glass became a symbol of wealth in Europe, with Bristol, England, emerging as a production hub. Here, over 15 glassworks crafted exquisite tableware and decorative pieces for the affluent, including royalty. This era marked a shift from cobalt blue’s luxury status to more everyday uses, especially in medicine and poison bottles by the 1860s.

The 20th century brought about mass production of cobalt blue glass, notably for Bromo-Seltzer bottles, a popular remedy introduced in 1888. This era also saw Vicks Vapor Rub and Noxema adopting cobalt blue for their packaging, extending its use into the 1950s. The Depression era further popularized cobalt blue through Hazel Atlas Glass Company’s creations, including the Shirley Temple mug collection.


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Cornflower blue glass, a softer variant, gained popularity in the 1920s and through the Depression, mainly used for Phillips’ Milk of Magnesia bottles and as part of the Depression glassware craze.

However, the advent of plastic in the 1960s dramatically reduced glass production, making cobalt and cornflower blue glass—and consequently sea glass—rarer. This scarcity, combined with the deep history and connection to both the natural world and human craftsmanship, is likely why cobalt and cornflower blue sea glass remains highly sought after today.

The Origins of Soft Blue (Foam) Sea Glass

At one end of the sea glass spectrum lies the deep cobalt blue, almost veering into black, while soft blue, with its gentle wash of color, anchors the other. Soft blue glass, prevalent through the 1800s and into the 1900s, reached its zenith from the 1880s through the 1930s. This lighter hue, distinct from its deeper counterparts, owes its existence to copper, which, in trace amounts naturally found in sand, originally lent glass this soft pastel shade. Glassmakers, capitalizing on this serendipitous discovery, soon crafted fruit jars, medicine bottles, and even ink and soda containers in this tranquil blue.

Soft blue glass often features a bubbled texture, a vestige of the era before 1920 when bottles were crafted by hand, making these thick, bubbly pieces especially prized for their ability to catch and scatter sunlight like the ocean’s surface.


The thinner fragments of soft blue might once have been part of windows or windshields, sharing the old-time bottles’ subtle blue tint. It’s important to note that soft blue stands distinct in the palette of blues, separate from its cornflower and cobalt relatives and the lighter aqua shades.

Additionally, the glass insulators, another relic of the 1800s through the mid-1900s, deserve mention. While most were made in a bright green-blue aqua, a rare few were crafted in soft blue. As these insulators were phased out in favor of modern materials by the late 1950s, many were discarded, ending up on the ground or in nearby waterways. Finding sea glass from these insulators is quite the treasure hunt, with their thickness and the distinctive grooves that once secured them to wooden poles offering a unique glimpse into the past.

The Rarity of Blue Sea Glass

Venturing to the shoreline often morphs into an unexpected quest for those captivated by the allure of sea glass. Your gaze might fixate on the intricate mosaic of pebbles and sand, momentarily losing sight of the sea’s vast expanse. Then, amidst the kaleidoscope of natural tones, you might spot a fragment that seems to harbor an inner luminance. The thrill of uncovering a shard of blue sea glass is akin to uncovering a hidden gem.

The joy of finding sea glass tinted in shades from the faintest blue to the depths of cobalt is a cherished rarity. Although the creation of cobalt blue glass spans centuries, its presence among sea-tossed fragments is notably scarce. It’s estimated that merely one in every 250 fragments bears the cobalt hue, with cornflower blue pieces being even more elusive.

While soft blue sea glass also belongs to the rare spectrum, it’s somewhat more common than its deeper blue relatives. It’s crucial not to confuse soft blue with the more greenish hue of seafoam glass, as each shade has its own unique lineage and charm.


Discovering a piece of blue sea glass, whether it’s strikingly vibrant or subtly pale, is indeed fortunate. For those unable to wander the shores in search of these oceanic jewels, there’s solace in acquiring sea glass jewelry, offering a connection to the mystery and beauty of these pieces.

With the growing fascination for sea glass, it’s important to be wary of market-saturated, artificially frosted glass posing as “Sea Glass.” Authentic sea glass is sculpted and frosted by nature’s own design, its form shaped by years, sometimes centuries, of oceanic embrace. True sea glass exhibits a unique roughness and a matte finish that artificial processes can’t quite replicate. Beyond its tactile and visual appeal, every fragment of genuine sea glass is steeped in history, making each piece of jewelry crafted from it a singular treasure.

Reflecting on Blue Sea Glass

As sea glass gains popularity, discerning between real and artificial pieces becomes crucial. Genuine blue sea glass, shaped and frosted by the ocean, carries a history and authenticity that mass-produced glass lacks. Collectors and enthusiasts value the unique characteristics and stories behind each piece of real sea glass, underscoring the importance of authenticity in their collections.

The journey of blue sea glass, from its origins in historical glassmaking to its transformation by the sea, is a testament to nature’s ability to repurpose and beautify. For those who seek it, blue sea glass is not just a fragment of glass but a piece of history, a work of art forged by time and tide, and a cherished connection to the natural world.



1 in 250


Baby Blue through to the Dakfest Prussian Blue.


From 1700s+


Medicine Bottles, tableware, decorative objects.

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