How to ensure your oven remains kosher

1. What is the purpose of this guide?

This guide will provide guidance on the means by which an oven should be used to ensure it retains its kashrus. The information is designed to advise on the day-to-day use of the oven as well as providing pre-purchase information so customers know the type of oven which is most suited to their kashrus requirements.

2. Can I use the same oven for both meaty and milky foods?

Once a food has been cooked inside an oven, the steam which is produced permeates the appliance’s walls. This flavour may then be extracted and be transferred to foods cooking during future cooking sessions.
For this reason, you should dedicate your oven for either meaty use or milky use. The following rules apply to an oven which has been dedicated for use of one ‘gender’:

• One may freely use the oven for its dedicated ‘gender’.
• One may make use of the oven for the other ‘gender’ only if (a) the food is covered with foil and (b) the oven is visibly clean and free of actual residue.
• A solid dry parev food (eg challah) may be baked in the oven uncovered as long as it is clean and free of residue

3. Can I kasher an oven from meaty to milky?

Kashering is the process through which old flavour is removed from a utensil or burnt. The process renders it free of previously absorbed food flavouring.
Kashering a meaty or milky utensil and making it parev is viewed more leniently than kashering a non-kosher item. Since meat and milk are both intrinsically permitted substances, kashering a meaty oven does not demand the same intense fire as is needed when kashering from non-kosher treif.
Kashering from milk to meat is prohibited, however, for other reasons. One therefore must follow the following guidelines:

• Only kasher from meat to parev or milk to parev
• Once the oven has been kashered for parev, it may then be used for meaty
• There is no need to run the pyrolytic setting to kasher an oven from meat to milk or vice versa
• To kasher, first clean the oven with a cleaning spray
• Burn out the oven on its highest temperature for 45 minutes
• This method of kashering should not be relied upon to cook an uncovered liquidy meat dish within 24 hours of cooking an uncovered liquidy milk dish

4. I am moving into a non-kosher rental property, can I kasher the oven?

The walls of an oven are viewed as having absorbed flavour from previous cooking sessions. Although some authorities are more lenient, the position of the Federation Beis Din is that if non-kosher food were cooked in an oven, there is a need to kasher the oven with an intense heat in a method called ‘libun chomur’. This step is particularly necessary when kashering the oven shelves and any area which may have come into direct contact with non-kosher foods.
The householder is generally not equipped to meet these kashering criteria, and members of the public are recommended to seek professional koshering assistance with this. See question 5 for a discussion of the ovens whose in-built self-cleaning systems are viewed as sufficient for kashering.

5. I have a self-cleaning oven is that sufficient for kashering purposes?

The term ‘self-cleaning’ is somewhat ambiguous. The temperature required for kashering a non-kosher oven is only provided by running a pyrolitic setting. Some ovens use ‘self-clean’ to describe a cleaning cycle which uses steam and though this may provide a pleasing hygienic result, does not meet standards required for halachic kashering.

6. Can an oven be kashered for Pesach?

The position of the Federation Beis Din is that ovens need ‘libun chomur’ for Pesach. The pyrolytic setting meets these requirements and allows one to kasher their chometz oven; where this is not available, a dedicated Pesach oven should be used.

7. Can I use a double oven – the top one for meaty and the bottom one for milky?

To allow the two compartments of a double oven to be used for meaty and milky, one would need to establish that the two compartments are indeed totally separate ovens.
If were to be demonstrated that the two compartments share a single sheet of metal which acts as a barrier between the two this would be problematic as food flavour from one session can be imparted into the cooking during the other session. Another potential concern is that the two ovens may vent into each other.

The incidence of these problems is rare and consumers can generally assume that the two cavities are entirely separate.

Nonetheless some Rabbonim advise that one proceed with caution when using a double oven. The careful approach suggests that foods be covered in the oven when cooking simultaneously meat and milk in the separate oven cavities. This is most needed if one of the foods contains significant amounts of juices/gravy as this will create a lot of steam.

8. What do I do if I have questions about this guide?

As always, if you require assistance, the ShailaText team of Rabbonim is available on 07403939613 .
Questions can also be forwarded to technology@federation.org.uk.