Frank Krygowski, 2018-04-26 17:50+0200:
The other common advice with this method: Don't heat the wax-oil mix
indoors over an open flame. Supposedly the vapors are flammable and any
resulting fire can be fierce and difficult to extinguish. So your gas
kitchen stove is out.

I already fought such a fire, due to the negligence of a friend that was
melting wax to make some torchs. It was on an electric kitchen stove,
but he left if unattended for so long that the was started to boil, and
the vapor autoignited! It made a flame of about one meter, which I
managed to shut off by simply covering it with a metal lid, and waiting
for the wax to cool down.

You clearly do not want that to happen in your kitchen, and it is useful
to know that it can happen even with no external flame.

--
Tanguy