Venmo, dishwashers, those Instagram filters that give tired faces a glow-up—we can all agree our world has benefited from progress. But some things don’t need to be improved upon. Case in point: pine tar.

Pine tar has been in existence since the days of the plundering-and-pilfering Vikings, who distilled the stuff in large quantities and used it to preserve their wooden ships. If it’s potent enough to waterproof these vessels that sailed the rough waters of the North Sea, it’s surely good enough to protect your wood fence, deck, garden shed, barn, or home.

To learn more about pine tar, we reached out to the folks at Earth & Flax and Sage Restoration, two North American companies that specialize in natural Scandinavian paints and wood finishes, as well as Emil Jespersen, cofounder of Danish-Norwegian architecture firm Jespersen Nødtvedt, who recently worked with pine tar on a project for a client.

What is pine tar?

Pine tar is a natural marine-grade wood preservative. Traditional pine tar was made by essentially cooking down pine stumps in fire pits to yield a syrup-y, dark-colored, and resin- and turpentine-rich liquid. Today, most pine tar products are produced in kilns (using heat only).

Post-Viking Age, pine tar is primarily used as a finish for decks, fences, facades, and roofs in Scandinavian countries, but interest in the wood preservative is growing in the U.S. “What’s old is new again. People are looking for alternatives to modern chemical finishes, and architects are looking for something new to offer clients,” says Michael Sinclair of Sage Restoration, which is based in Tamworth, Ontario. “Our sales have been increasing every year.”

Natalie Yon Eriksson, founder of Philadelphia’s Earth & Flax, agrees. “This trend is going strong. Pine tar has been used with or in place of the traditional Japanese shou sugi ban burned or charred siding treatment,” she says. “The best aspects of pine tar are that it is sourced from nature, using a waste product from the timber industry, and is an exceptional natural wood preservative.”