We made our mittens using lard and plastic bags.
We held our mittened hand and bare hand in cold, icy water and compared the temperatures.
It can be quite sore to hold your bare hand in very cold water for too long!
We noticed how red our bare hand became.
The hand in the blubber mitten barely felt cold and wasn't uncomfortable at all.
No wonder Arctic animals who have a layer of blubber don't feel the cold!