Cameron C. : The Rocket Mass Heater and even the rocket cook stove burn at much higher temps than a metal box
wood stove can sustain, therefor
the biggest part of the
ash that your
Rocket Mass heater will make will be fly ash, very little lye will be found in its ash !
Remember, Lye is a caustic substance, a strong base, and proper protection most be worn and no metal containers or stirring sticks/paddles can be
used !
There
should be several good articles available on safe Soap making ! for the Good of the Crafts ! Big AL