https://www.youtube.com/watch?v=a9XSxgQhNJ0
https://www.ebay.com/itm/284744346674?hash=item424c15ec32:g:EtIAAOSw5BZiSl3Q
Mags
Want to do this for free drop some limestone or black schist into your firepit
After its been heated for a while you can crush it and drop it into water.