I prefer the 36 gauge copper foil over the 40 gauge, because it is
thicker and less apt to rip. However, it is more expensive and takes
more pressure to work. Sometimes my students need to give their poor
fingers a break. I usually keep the size no bigger than 6" x 6" per
student (a roll is 12" diameter.) The state of my budget decides whether
or not I order the 36 or 40. A roll will also last me about 2 years.
Wooden ceramic tools work well on the copper, too. Hope I've been
Brattleboro Area Middle School