This is a very versatile technique in which you use a special tool (a gripfid) to split the plies of a yarn, and then feed other yarns back through. You can do some pretty amazing colorwork and stitch patterns with it. Everything I've made so far has this very pleasant and unusual "squishiness" to it. Most commonly it's done with 4-ply yarns, splitting them in half each time, but there are tons of other variations. Linda Hendrickson's books on the topic have been a huge help! Something I do that I don't think I've seen mentioned elsewhere is dipping the free ends of the yarn segments into hot wax. This keeps them from fraying as you work, makes them easier to insert into the gripfid, and makes them less likely to come loose.
I went with cotton, thinking how quality undergarments are usually made from that. Hopefully that was a good idea, would synthetics have been better?
I have zero experience in the area, I would just assume synthetic material is less likely to let anything grow on it? might be talking out my ass because you're correct about underwear
I live in Miami so I'm sort of hypervigilant about swamp crotch
It definitely sounds like a good point to me though! Luckily I designed it to be washable, hopefully that'll do? I'm in Philly which definitely has its hot and humid day, but probably not as bad as Miami does lol.
it's nice that it's removable so you can dust it with baking soda as needed. I wish mine did that