You Asked:
How do they weave t-shirt fabric into tubes without a seam? — Charles, Shanghai, China

Marshall Brain Answered:
When most people think of a loom, they think of the traditional back-and-forth variety like this:

The loom creates a flat piece of fabric. If you were to make a T-shirt out of flat fabric like this, it would have to have a seam.

But it is fairly easy to make a loom where you bring the two ends of the fabric together and weave the fabric as a tube. You gain a big advantage here – the shuttle doesn’t have to reverse directions. A circular loom looks like this:

T-shirt fabric is woven on a tubular loom like this. The fabric for small, medium, large and extra-large shirts comes off looms with different diameters.