What do you look for when you're buying clothes? Cut, colour, brand name? Well they're all irrelevant when it comes to sailing gear, particularly jackets. What you should really be checking out is waterproofing. Those Gore-Tex jobs you've seen in the shops. And have you ever thought about how Gore-Tex works? Since it's kind of important, here's a brief guide to the world of waterproofs.
To understand all the high tech stuff, it's back to school and a simple principle of chemistry. Out on the water you need to keep dry, not just from the water around you, but from moisture generated by your own body, politely known as perspiration. That means not only keeping the water out, you've got to let the sweat out too. This was the poser that clever scientists at Gore-Tex put there heads together to solve in 1978 - to find a waterproof and breathable fabric. Their answer was osmosis.
Osmosis is a term for the movement of a solvent through a semipermeable membrane into a solution of higher solute concentration, thus tending to equalize the concentrations of solute on both sides of the membrane. Make sense to you? It might be Japanese for all I know, so let me translate. In sailing terms, "solvent" becomes water and keeping it out is easy enough to understand. But sweat is something else, making you hot and clammy from being trapped inside your coat, high concentration inside versus low concentration outside. To balance things out, Gore-Tex brilliantly keeps water out and lets vapour escape through the fabric at the same time. No sweat, see?
Most waterproof fabrics include a semipermeable membrane. The clever bit is how it lets some substances pass through and keeps others back. And of course the best-known example is from Gore-Tex, since they came up with the idea. Gore-Tex waterproof jackets have a thin plastic film with billions of microscopic pores that are big enough to let water vapour out to keep you cool, but small enough to prevent water liquid, like rain or spray, coming in. That's water in two different states - held apart, but not prevented from reaching each other - so you keep dry and the fabric is waterproof and breathable.
“But wait,” you say, “there's water vapour on the outside too.” And yes, you're right - you only have to breathe out on a cold morning to know there's vapour in the air all around you. Aha, those Gore-Tex scientists are smart too, and have come up with polar molecules to sort out the equation.
Each molecule sits on opposing sides of the film; hydrophobic on one side and hydrophilic on the other. The words come from Greek; 'hydros' meaning water and '-phobic' translating to fear, '-philic' to friendship. So how does this apply to you? Well, to keep you dry, the hydrophilic ones are positioned inside, towards your body. They're like little water magnets and attract the moisture (or sweat) in the air around them onto the fabric. Once they've been absorbed, they're whisked through to the hydrophobic side, which as you've probably guessed doesn't like water at all. In fact it actively repels it. And thanks to the polar molecules, it's as if all the microscopic pores in the membrane film are one-way valves. The sweat can get out alright, but the polar molecules won't let it back in.
Now maintenance. Waterproofs aren't like other fabrics, so you should always use a technical wash whenever possible. Just chucking 'em in the machine will seriously reduce the life of your jacket, because enzymes in the detergent and other biological elements in the powder destroy the polar molecules and kill the valve effect. You might not notice it if a bucket of water was chucked over you, but the inside of your jacket would be damp. Without one-way control, water vapour can to move both ways through the material.
It's not a disaster if you have already washed your jacket in normal detergent though, because there's a wide selection of reproofing products you can get. They're not as affective as the original Gore-Tex, but will sort things out as long as you repeat the process every couple of months. Don't buy bargain basement tech-wash or reproofing products, go with one recommended by the manufacturer. And NEVER buy a tech-wash and reproofer in one. This will waterproof your jacket on both sides, inside and out, sealing it and rubbishing the whole osmosis action. My own choice is for a spray-on reproofer to spot trouble areas on the outside, without affecting the inside of the jacket like the wash-in versions do.
If you don't want to splash out on a brand-name product, you can hand-wash just as effectively with a non-biological, non-detergent wash. The best is to use pure soap flakes, as this won't harm the fabric in any way. If you only need to do spot cleaning, a baby wipe is your best bet for the same reasons.
So now you're a graduate from The Main Sail School of waterproofing, do you feel enlightened? I hope so, but if you want to know more, check out Gore-Tex at www.gore-tex.com. If the high-tech grabs you, or you want to find out more about the science, have a look at howstuffworks.com.
