Small battery powered heating element for Biology experiment?
I would like some help designing a small heating element. It will be battery powered (and voltage hopefully 3 or 4 C or D batteries).
It should fit on the top of a quart mason jar, as I will be heating the milk inside to about 90 degrees Fahrenheit for a period of one week. I would hope that battery changing is not necessary, but if so, any help is wanted. I have soldering skills, and would prefer to make as much as possible by hand. I also have lots of spare parts and wires, as my dad is an HVAC Chiller Mechanic.
A coil of wire attached to batteries slid through holes in the lid might work?