Plastic Bags DO Work :-P
Yesterday morning I was heading out to ride in temperatures in the upper 30s to low 40s. Normally, I would wrap my feet for all they're worth, since I simply can't keep them warm to save my life. Usually that would consist of some poly liners, wool socks, chemical toe warmers, shoes, then neoprene booties. My shoes are laced, so I can loosen them up enough that I'm not cutting of circulation. Even with this I would still get cold feet after about an hour in temperatures below 40°, but I tried something different this time.
The first thing I put on my feet this time were plastic grocery bags. I just slipped my wool socks over them to hold them in place, then tucked the extra plastic in the cuff of the sock. I still put chemical toe warmers in my shoes, but that's all I wore this time, and my feet were quite comfortable. The plastic was a bit itchy at first, but once my feet generated some sweat, it felt fine.
I also tried some latex exam gloves under my mid-weight winter gloves, which are usually only good down to the mid or upper 40s. This didn't work as well, since I suppose the latex does still breathe some? The point of the plastic is to keep the sweat against the skin, instead of letting it soak the insulating layer. I think my gloves still got a little damp, or maybe the tightness of the latex gloves prevented a sufficiently insulating layer of sweat from forming.
An interesting experiment nonetheless. I'll definitely try the bags again for colder weather rides.