The Thermal Stitch is by far the best stitch (that I know of) you can use to crochet a thick potholder. It's quite dense and thick - it's basically double the thickness of a normal single crochet. It's perfect for a potholder or anything that needs that extra thickness. When trying this stitch for the first time, the trickiest part is to find the right stitch that you need to crochet into. The whole pattern consists of Thermal Single Crochets (single crochets that are worked into the back loops of current and previous rows together). That's what creates the thickness.
