Carlo Colombo achieved the ultra-thin lines of the Baia tub, for Antonio Lupi, using Cristalplant, a completely recyclable solid surfacing made from hypoallergenic, non-toxic minerals and acrylic resins. While it is designed with the look and velvety feel of natural stone, Cristalplant has a practical advantage: it is highly durable, UV resistant, non-porous and easy to clean. ­antoniolupi.it

This free-standing model is shaped to fit the body’s contours, resulting in a curvaceous form that reduces water use by taking 56 litres less than a standard tub to fill. The company says that its proprietary Englishcast, made of volcanic limestone ground and mixed with resin, provides thermal insulation, so you don’t need to add steaming water if you want a good, long soak. ­vandabaths.com

If you’re going to make a wooden tub, you might as well use the best boat-building material on the planet. Italian design studio Plavisdesign’s Day Evo tub, for PierDeco, is made of FSC-certified okoume, a durable yet lightweight marine-grade plywood used for Formula 1 race boats, kayaks and even hydroplanes. The reason: it is highly resistant to heat and humidity. ­pierdeco.com

Designed by Patrick Messier, the limited edition, sea-shell-inspired Couture tub, by Wetstyle, is made of the manufacturer’s proprietary Wetmar Bio, a thermo-insulating compound that replaces the usual petrochemical resins with soy and mineral stone. The result is a non-porous, slip-resistant and exceedingly durable alternative to ceramic. ­wetstyle.ca