alcohol lamp (going on 45 minutes with mostly 70% and topping off with 99%–end went an hour 5) underneath the metal table (some heavy duty aluminum foil to protect the finish?). heats the table. and upside down empty beer can filling with warm air. crinkled edges to increase sheltered surface area. then an upturned beer can, crinkled, about 1/3 water (probably should be less a little), maybe add salt to it so that it retains heat more. heat the table to keep warmer when outside working.
need to dilute 99% alcohol as the flame is TOO large and out of control.
50/50 mix is good. if you want to prime the alcohol lamp, then heat it from the bottom (like a fire underneath it).