Cotton is no longer king, at least when it comes to bath towels. According to our latest tests, those woven from a new, touted blend of cotton and bamboo were about 25 percent softer after laundering, on average, than their all-cotton counterparts.

If you’re picturing strands of bamboo woven through the cloth, don’t. Actually, cellulose from the panda’s favorite food is often converted into silky rayon fibers, and it’s the rayon--which can also be created from cotton or wood pulp--that can lend a softer feel. Unfortunately, soft isn’t cheap. The four bamboo-blend towels that we tested averaged $23. That’s about $8.50 more than the average 100 percent cotton towel.

Because bamboo grows fast and can be harvested quickly, some blends purport to be more “eco-friendly” than cotton towels. That’s a dubious claim, however, since the production of rayon requires the use of caustic chemicals.

We tested 25 bath towels for softness and shrinkage after five washes, fading after 50 washes, and bleeding after the first wash.

What we found. Ten towels, listed in Ratings, were very good overall. Many scored very good or excellent for softness and shrinkage; none showed excessive fading or color bleeding.

Whichever towel you choose, you’re apt to get more of it: The ones we tested were 7 percent larger, on average, than those we looked at seven years ago. (Credit inexpensive outsourced labor as the reason for this change, not the American waistline, which grew an average of about 1 1/2 inches between 1988 and 2002, according to the federal Centers for Disease Control and Prevention.)

A problem that manufacturers haven’t quite solved causes what our testers term “bonbons”--towels that shrink across the end borders but not across the middle, making them look like wrapped candy. The Charisma Egyptian, and Lands’ End Cotton/Bamboo and Elite Supima towels in our Quick Ratings were particularly apt to bulge.

How to choose. Check the Ratings, because it’s hard to assess a towel’s softness in a store. Most manufacturers finish towels with fabric-softening “hand enhancers” that wear off after a wash or two. Be aware that thicker, heavier towels are generally more absorbent than thinner, lighter ones but also take more energy and time to dry, and occupy more space in a closet.

Buy an extra washcloth and stow it unwashed with your receipts. That way, if the towels fade and you need to return them, you’ll have a control that supports your claim. A final caveat for homes with teenagers: Benzoyl peroxide, in many acne products, might bleach towels and leave an orange or pink blotch. For kids who are using such creams, consider very inexpensive towels. Martha Stewart Everyday (Kmart) 3-Star California Cotton towels, $5 per bath towel, were rated good in our tests. See our primer for towel terminology, such as “backing” and “two-ply.”

Liquid fabric softeners leave a film on towels that decreases absorbency and increases flammability. Use dryer sheets instead.