If you’ve ever spent an afternoon crouched on the pebbled shore at Seaham, eyes glued to the tide line, you know the absolute thrill of spotting a multi. Unlike your usual smooth greens or soft whites, these multi-coloured gems look like little drops of painted glass art. Red swirled with yellow, cobalt streaks through milk-white, or deep teal blended with soft amber—no two are ever the same.
But how on earth did these rainbow-hued pebbles actually end up on a quiet stretch of County Durham coastline?
The World Capital of Glass Back in the Victorian era, Seaham wasn't just a picturesque spot for a chilly dog walk; it was a booming industrial hub. In the 1850s, the Londonderry Bottleworks opened right on the seafront. At its peak, it was one of the largest glassworks in the entire country, operating six massive glass houses and producing millions of handmade bottles, decorative vases, and household wares every single year.
Seaham Bottleworks
What Actually is "End-of-Day" Glass? At the end of a long shift, glassmakers would clean out their pots to prepare for the next day's work. Instead of letting leftover molten glass go to waste, workers would mix the remaining bits of coloured glass together. Sometimes they did this just to clear the vats, and other times they made whimsical glass ornaments—like slag glass dogs or decorative paperweights—to take home to their families.
Any unusable scrap, molten slag, and discarded ends were simply tossed off the cliff edges straight into the North Sea. To the Victorians, it was just industrial rubbish.
How the Colours Came to Be The vibrant, layered bands in Seaham multis are a direct snapshot of Victorian chemistry:
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Whites and Opals: Created using bone ash or tin oxide to make translucent, milky glass.
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Vivid Reds and Pinks: Achieved using expensive ingredients like real gold chloride or copper.
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Deep Blues and Purples: Tinted with cobalt and manganese.
When these molten colours were dumped together, they swirled like paint in water before setting hard.
100 Years in the Ocean's Tumbler When the bottleworks finally closed its doors in 1921, millions of these discarded glass chunks were left behind at the water's edge. Over the last century, the fierce tides of the North East coast have acted as a massive, natural rock tumbler. Decades of heavy waves, rough shingle, and harsh weather smoothed down those sharp, jagged lump of factory waste, rolling them into the velvety, frosted jewels we hunt for today.
If you ever spot a multi gleaming in the wet sand, you aren't just finding a pretty pebble—you're holding a tiny, polished piece of local working-class history.
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