Why would a project knit with new wool yarn 'join' after a wash? ....details...?

One way that wool felt is made is actually by agitating it (thus creating friction) in warm, soapy water. This causes a small fraction of the wool fibers to move in alternating angles to and from the friction source, which causes the scales on the surface of the hairs to lock together, thus yielding felt. Only a small fraction of the fibers do that any one time, but the longer the agitation occurs the more and more pronounced the effect will become.

Thus, I would suggest:

-Wash in the coldest water you can

-Use the least amount of soap that you reasonably can

-Use the gentlest wash cycle you can

-Use the shortest wash cycle that will get the job done

The same reason why wool can felt in your washer is the same reason you shouldn't dry it in a dryer, as in a dryer there's a lot more friction and heat involved, and the wool is still wet/damp through part of the drying process.

The finer the wool fiber you're using, the easier felting will occur. There are ways to treat wool to minimize the felting process by essentially locking down the scales, but I'm not sure if there are any processes that are feasible for at home use. I'm not sure if there's yarn you can buy that is already treated (I've admittedly never purchased yarn in my entire life, I just stumbled across this question because a contact starred it).

Here's some scanning electron microscope pictures of the scales: http://ars.els-cdn.com/content/image/1-s2.0-S00143...

Pure wool is what felts. Wool/synthetic blends are less likely to felt, although there is still a slight chance of it happening. Switching brands will not change the felting. There is nothing wrong with the brand you used. No, you don't have to get your projects dry-cleaned, but you should always wash hand-knits by hand. I even wash synthetics by hand, just to make sure they retain their shape and don't pill. As for your present projects that have felted, I'm afraid there's nothing you can do. Once they have felted, it's permanent. I found this out at age 15 when I threw a nice yellow wool sweater in the wash, and it came out the size of a teddy bear sweater! :-(

The agitation of the washing machine probably felted your project. To avoid this, when you clean your project, use a mild soap (such as Woolite) and soak it for a few minutes in cool water. Gently squeeze the soapy water through the fabric. Don't agitate! Drain the soapy water, refill basin with fresh water, and squeeze the water through again. Repeat if necessary, then roll it in a towel to remove the water. Lay flat to dry.

In the future, look for superwash wool, which won't felt.

Did you rub the item you were washing.

It is friction which felts the yarn not heat.