Thought for the Day: Sh'i'ah, Chazarah, Tanur Kira -- Ovens Today

Of course I know that wood burning stoves don't have knobs to adjust the temperature.  Of course I also never really thought about what that meant for bakeries in days gone by.  Baruch HaShem, I had the z'chus to once hear first hand from someone who lived in pre-war Europe and who's mother ran a bakery.  There are all sorts of "little" details.  For example, not only was there no way manually to adjust the temperature, there was also no way to turn it on and off.  You started a fire and let it go till the end; wood is an expensive resource, after all.  The process he described took careful planning and then about a week of execution.  Breads at the beginning of the week when the fire was hottest, then cakes and kugels as the temperature came down, finally pastries and other delicacies that required lower temperatures at the end of the week.  That's a heck of a lot more than "no temperature dial".

That insight, I found, has been very helpful in understanding the laws of sh'i'ah (leaving food on/in the oven over Shabbos) and chazara (returning food to same).  To make things more complex, the Shulchan Aruch discusses three kinds of ovens: kira, tanur, and kupa.  Besides the fact that they were wood/coal fired and had no dials, they also were open on top and the pots were lowered into them.  Basically, they didn't look much like our modern gas/electric ovens that open from the side.  Also, just so you don't get bored, these halachos are based on a machlokes Chananya and Rabanan that has no resolution, so the poskim have had to try and cover all bases.  Siman 253 (which contains the bulk of this discussion) is only five s'ifim; very long and complex s'ifim.  The Dirshu Mishna Brura on this siman, which usually has up to one page of expounding on the Mishna Brura, adds additional full pages in the text which then continue onto another few pages added as and appendix.  Not for the faint of heart.

This is obviously not the venue to go through all that, but I did finally realize that there are two basic concerns driving the the discussions which helped me to manage all the details.  The two basic concerns are:

1. Safeguards to prevent one from accidentally stirring the coals.
2. Preventing situations that look like the normal way of cooking.

To take a small example: suppose you want to leave one burner on through Shabbos.  There are no coals there, but clearly adjusting the dials is similar to stirring the coals, so you might think that simply covering/removing/locking the dials would be enough.  However, putting a pot on an uncovered burner the the normal way of cooking.  Most poskim, therefore, require a blech that both covers the burner and protects the dials from being (easily) adjusted.  For a crock pot, that means lining the heating receptacle with foil (not a thin layer, but enough to effect a temperature difference) and taping the knob.

Oh wait... then there are also hatmana (insulating) issues.  Darn!  Out of time and space.  Have a wonderful Shabbos and Chag Kasher v'Samei'ach!