FWIW on the tape baker, Chuck Guzis always used to recommend a 25W bulb in a cardboard box for a few days. Should be easy enough if you have any old 25W bulbs still kicking around. - Dave Riley
Home Depot offers 15W and 25W incandescent bulbs. The heat produced may depend on the size of the box. Dave Riley, do you recall details? Maybe a temperature set-point? I think I could design a relay and a 555 as a controller. But for warm environments, people use things like rice-cookers, crock-pots, dish warmers; thrift store items. My wife dyes fabrics overnight in a bowl, inside a covered container with a layer of water, on a dish-warmer. A stable, but wet, environment. Pebbles could provide dry thermal mass, seems to me. - regards Herb -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net