SPF clothing-how it works

I have always wondered about clothing that have a SPF labelling. Has the fabric been treated or type of weave??

Just bringing this topic back up..in case, for reconsideration.

methinks you should research and get back to us. Perhaps none of us know the answer.

link that might help:
http://www.coolibar.com/sunprotectiveclothing.html

Not necessarily.

All clothing provides some measure of sun protection, as anyone who has ever gotten a farmer's tan can attest. Most clothing, in fact, does a pretty good job of protecting you from the sun. The clothing that has come to the market over the past 10 years or so seems to be different in only a couple of things--first is that they test the clothing to verify it's level of protection and second is that they focus on making the clothing lightweight/cool. Obviously I could wear leather head to toe and have 100% protection from UV rays, but I'd be miserable. And I can happily wear a lot of the clothing I already own and get exactly the same protection that I'd get from a Solumbra shirt, but there wouldn't be a label telling me my level of protection. The UPF rated clothes seem to provide a high level of protection with very lightweight and comfortable fabrics.

I know some of the early types of clothing had a coating on them to give the sun protection, but the coating would wash off after a while (and too soon if you didn't follow the washing instructions carefully) so I think now what we're seeing is some of the more technical fabrics being developed and used for more "normal" looking clothes that provide that kind of protection.

Sarah

It's all in the weave. I've had 100% cotton clothes that were SPF rated...but I'm nearly incapable of burning, so I gave up on them...

With lightweight SPF clothing, I find that I still get sun through it. So I still wear sunscreen. But I do live in Hawaii where the sun is very strong, especially this time of year.