what type of cloth that can protect the skin against UV A, B?

I don't want to catch cancer. I also use sun screen but I want to know if there existing cotton shirt can shield the wearer from UV rays.

http://www.rei.com/expertadvice/articles/sun+protection.html

This article has some decent information, including which types of fabric block better or worse, and general ratings based on material and weave, among some other factors.

you might check the sport fishing shirts (flats fishing) with open cape back...most will have an SPF rating...most of mine are DuPont Supplex nylon... not sure how long the process lasts

my first basal cell carcinoma showed up on the top of my ear... wear a brimmed hat..have a yearly visit to your dermatologist..

I always thought any cloth would protect against UV rays.

I have some of the new columbia SPF rated shirts and I cannot tell any noticable difference except the stupid price. I don't think the type of cloth is as important as the fact you cover yourself up with something.

I have no reference for that, just from experience.

+1.

My understanding is that indeed, "any cloth" will provide some protection against UV. With the advent of SPF numbers, providing a number for your product clothing has become a marketing point; but even a thin cheesy T-shirt will be better than bare skin exposed to sunlight. On the other hand, well applied sun screen beats thin clothing.

My experience has been that simple white cotton works for me just fine. The denser the weave the better. Oddly, a 100% cotton long sleeve white dress shirt is high up on the list. A thinner, white cotton T-shirt less so.

I think sometimes we worry too much about "the best" solution when there are simpler solutions that work, perhaps not "best," but on the whole, just fine.

That is a good article especially the latter part. To encapsulate, these are the factors invovled in UV blocking clothing:
Construction
Dyes
Treatments
Fiber type
Stretch
Wetness
Condition
to which I also add body movement and shifting of the fabric.

I believe that a tighter weave or a thicker fabric is inherently more UV protectant than a looser cloth. I read somewhere that a typical cotton T-shirt provides approx an SPF equivalent of 15. That is helpful but it doesn't protect from exposure to the hands, arms, neck and face. I never wore sun screen when I was younger and now I have a permanent farmer's tan. That's where additional sun-block can come in handy on those surfaces and indeed underneath the clothing as well. Often it is recommended to use a higher SPF sunblock of 30/40 or even 60 while staying out in the sun all day.

I've always promoted the use of wide brimmed hats (like my Tilley) and sunglasses to protect myself an I normally wear a synthetic weave as my base layer instead of cotton. I have no idea if they are specifcally treated for UV protection and I don't purchase clothing with that in mind in particular.

Note: as I get older and my forehead keeps growing I find I definitely need to wear a hat of any kind to prevent overexposure as I seem to burn and peel very easily up there. YMMV.

Here is a good article on the subject by the Skin Cancer Foundation:

Sun protection from clothing

Good article. I was surprised to see in the article that a green t-shirt provided better protection than a white one. I would have instinctively believed white would be better but they pointed out how much difference dyes, weave, etc. can make with UV.