Garufa U'Ketuma

Rashi seems to say that sweeping or covering the coals makes a kirah fit for leaving food on before Shabbos, because the heat can no longer rise. Yet Rashi himself explains that wrapping food in ash mixed with coals adds heat. So how can covering the coals with ash help?Working through garufah and ketumah in Maseches Shabbos at Kollel Beis Hillel, Rabbi Asaf Prisman asks what Chazal were after: a cooler fire, or a heker showing a person has taken his mind off stoking the coals? The Rambam's wording matters, and a clean answer turns out to carry a new question.The quality of the audio has been worked on as much as I can. If anyone wants to help, they can send an email to admin@prismoftorah.com.