Here in Wisconsin, warm mittens are a winter necessity. My current system is to use two layers: a soft inner mitten knit in fine yarn under a heavier outer mitten in coarser wool.
Most of the year there is a pair or two of socks or mittens in my work basket. I knit them on four needles in the round and weave together the tip of the thumb and hand. I use wool yarn, the original performance fiber, for active outdoor wear.
Material: Brunswick 100% Shetland Wool, spun in Scotland
Children deserve warm wool mittens too! If your baby has graduated from thumbless mittens, these are the next step. They have a generous 2.5 inch cuff in K2 P2 ribbing to tuck into snowsuit sleeves. The thumbs are set directly on the sides, so your toddler can be a "big kid" and dress themselves without having to bother about left and right hands.
These are made in a woolen (lofty) yarn which is between fingering and sport weight, knit at a gauge of 7 stitches per inch. The shade is primarily rose red with golden and violet tones. Made in fall 2003.
See my Mittens Blog for a day to day diary of making a pair of red mittens in fine yarn.