A lokacin fashewar foda na magnesium, wasu barbashi na magnesium da aka dakatar suna kunna wuta akan hulɗa da tushen zafi, samar da iskar gas mai ƙonewa da cakuda oxygen. Wannan konewa yana haifar da zafi, tura samfuran iskar gas masu zafi a cikin yankin preheating da haɓaka yanayin zafin abubuwan da ba a ƙone ba..
A lokaci guda, zafin zafi daga zafin wuta mai zafi a cikin yankin amsawa yana ƙara ƙwayoyin magnesium’ zafin jiki a cikin preheating yankin. Da zarar sun isa wurin kunna wuta, konewa fara, da tashin matsi yana kara saurin konewa. Wannan tsari mai maimaitawa yana ƙarfafa yaduwar harshen wuta da amsawa, yana haifar da karuwar matsin lamba kuma a ƙarshe yana haifar da fashewa.