The Warmest Wetsuit Lining Ever?

Over the years, wetsuit manufacturers have tried various linings to improve strength, warmth and comfort, such as Lycra, plush, and brand names that sound metallic -- titanium and Henderson Gold – but aren’t. The latest innovation is a material mankind has been using for more than 2,000 years – wool, particularly from Merino sheep.

This super-wooly animal first became valuable when Arab Moors brought flocks into Spain. During the Middle Ages, its wool was so prized that it was made illegal, on pain of death, to export a Merino sheep from Spain, lest it break the kingdom’s dominance of the wool trade. The intensive grazing of Merino sheep stocks in those years gave Spain the stark landscape it has today. Nowadays, the finest Merino flocks are found in New Zealand.

Merino fleece has particularly soft, strong and extra-long hollow fibers. Its hydrophobic outer scales and hydrophilic inner cells keep the sheep -- and those wearing garments made from their wool -- extremely warm and dry. British designer John Gordon, who has been developing wetsuits for more than thirty years, tried Merino as a suit lining and concluded that it outperforms synthetic materials in thermal efficiency. The lining helps to reduce water movement inside the suit, and it’s incompressible, therefore unaffected by depth. Gordon claims that the wool is exothermic, so it produces heat as it gets wet.

Pinnacle Aquatics, based in Livermore, CA, is the sole manufacturer of Merino-lined wetsuits and drysuits. In its ads, Pinnacle touts tests by the British Textile Technology Group (BTTG) that state the wetsuits offer a 35 percent increase in thermal efficiency over synthetic linings. However, Pinnacle doesn’t mention in the ads that it commissioned those studies. Researchers took two neoprene samples, one with Merino lining and one without, wrapped them between metal plates and immersed them in cold water. Then electrical currents were used to generate heat in one of the plates; the amount of heat detected in the other plate revealed the insulating properties of the sample. For comparison, the test was also conducted in a dry state. BTTG’s results found that the Merino-lined neoprene resists thermal change 35 percent better when wet and 35.2 percent better when dry.

Will You Smell Like Wet Sheep?

It’s one thing to test fabric swatches in a lab, but no study has been done on humans in a variety of garments to show similar results. What about the itchiness associated with wool, like those scratchy sweaters Mom made you wear? And what does peeing in a Merino-lined wetsuit do to the wool?

“I have seen no test results published in a reputable journal, I’ve only seen marketing stuff,” says Bob Stinton, vice president of engineering at Diving Unlimited International, a rival drysuit manufacturer. He believes polyester and polypropylene garments still beat wool garments hands down. “Wool fibers have little burrs on them, much like thorns on a rose stem, and these burrs give wool their scratchy feel,” he writes in a letter on his company’s Web site titled The Truth About Wool as Drysuit Insulation. “They are why silk is used as a layer under wool garments. Silk does not have any great insulating property; its primary purpose to eliminate the scratchy feeling.” Stinton also writes about how lanolin, the natural oil in wool that keeps sheep dry and warm, is also odorous, can make those wearing wool in watery conditions “smell like a herd of wet sheep.”

Pinnacle Aquatics’ president George Stauffer issued a quick rebuttal. “Though lanolin is present in raw, unprocessed wool, Pinnacle’s Merino lining system contains zero lanolin,” he wrote back in a detailed, six-page memo titled Setting the Record Straight About Merino Lining. “Just as the synthetics industry has moved technologically forward, so has the wool industry’s ability to harvest and process wool, particularly merino wool. Today’s merino clothing is not only soft and warm; it doesn’t have any more particular odor than any other fabric….Merino’s excellent moisture absorption and uneven structure prevent the buildup of odor-causing bacteria, whereas these bacteria thrive on the exposed surface of synthetics.”

Stauffer says the “little burrs” concept is incorrect. “Wool fibers do have scales, but these scales don’t have anything to do with the scratchy feeling that some wools create. Merino is not everyday wool, it is a very specific type with an extremely fine micron count, and is so soft that it is often used to make baby clothing. Some cheap wool garments may have a scratchy feel, but they are not made of merino.”

Back and forth among rivals doesn’t prove anything underwater. Feedback from divers does. Undercurrent asked several divers who’ve used Merino-lined wetsuits for their thoughts. All of them were positive. Subscriber Jeff Rose (Harrison Township, MI) says a merino-lined suit is an outstanding option for divers easily chilled in water temperatures below 80 degrees. “I have purchased quite a few suits to try to keep my wife warm. Her last suit was a two-piece 3mm O’Neill Farmer Jane. Unless the water was at least 82 degrees, she used both pieces, and still called many dives at 40 minutes because she started to get chilled. I purchased a Pinnacle Fusion 5/4 before our trip to Fiji last fall. And guess what? She made 15 dives during the week in 79- degree water temperatures and never once was cold. In fact, she said she was often a bit warm. For many people, this suit would work well for temperatures into the upper 60’s with a hooded vest.”

An Expert Diver’s Underwater Test

Undercurrent works closely with the British magazine Diver, which has sizeable resources to test diving equipment and is known to do so without bias or favoritism. John Bantin, Diver’s technical editor, tested a Pinnacle Aquatics Polar merino-lined suit while at the Red Sea during the winter. The suit is a one-piece design made with a mix of 5mm and 7mm neoprene, plus a front-entry zipper. Soft latex seals at the ankles hold water out, and long outer cuffs can be zipped down over dive boots. A chimney seal in the sleeve and wrist cuffs with O-ring-type seals at the ends also reduce flushing. Bantin found the Merino lining absorbed and retained the water that did enter the suit, creating a waterlogged layer between his skin and the suit, which can add up to 3mm of extra insulation.

Merino wool is knitted into a tough cloth but according to Bantin, “It doesn’t feel itchy against the skin because the wool is so fine, and because of its ability to draw water away from its surface it doesn’t really feel soggy at all,” even when being donned again after a dive.

The Polar suit is cut with pre-bent arms and legs, and gussets on the inner curve of the elbows and knees give mobility. When he slipped on the attached hood and closed the chest zip, Bantin says he felt “well-insulated from the outside world.” He needed no help getting in and out of his Polar and says, “It proved to be one of the most comfortable and effective suits I have ever used -- almost as warm as a drysuit but as unencumbering as a wetsuit.”

There were only two downsides, he says. The first was “the extra lead I appeared to need to carry to counteract its natural buoyancy.” Second, “I got a bit of grief from the boat captain for taking 75 minutes over a dive while the others were coming back well within the hour, but he was confusing me with someone who was not relishing the comfort of this suit.”

“I can definitely tell you it is not a substitute for a drysuit,” Bantin reported. “However, it is a very warm wetsuit and I would say it is good (for me) down to 68 degrees. Someone with more body fat would probably be happy to use it in 61 degrees.”

Since his test, Pinnacle has begun marketing its Extreme model, originally designed for commercial divers, to the retail market. With 8 mm neoprene in the torso and 6mm in the extremities, it has the Merino lining and other features of the Polar suit, along with Kevlar kneepads, rubber shoulder pads and abrasion-resistant exterior material. The price is $543, compared to $480 for the Polar. Contact Pinnacle Aquatics (925-606-8300 or www.pinnacleaquatics.com) to find a local dealer (Pinnacle does not sell its suits by mail order). Most dealers don’t stock a full selection, but you should be able to check out the suit’s construction and lining, then place an order through the dealer.

-- Larry Clinton