Boil Water on a J-Tube Stove - PEP BB rocket.sand.jtubewater

Boil water 4L is a little more than a gallon so 2 pop bottles will be a gallon passed through the much smaller pan. The 1st pot I sterilized the pee cups. 2nd pot boiled water and then drop egg in boiling water it cracked in 2m. Then I poured the boiled water in my vegi broth. Put a raw egg with the cracked one to boil in the last pot.

May I make a temporary j-tube stove from brick/stone and use it to boil water for this bb?  It would not be welded together with metal.  It would not (although I could) have cob to seal it.  Just brick or stone stacked to make a j-tube stove to cook on.  I'll use it to cook outside when it's too hot to cook inside.

Thanks, Tina

You may, just make sure it is a J-Tube.