One of the most misunderstood aspects of Kashrut is the issue of utensils. How can a utensil become non kosher? How can it be made kosher again? (n.b. the almost universal folklore of burying a utensil over night has absolutely no basis in halachah. You can take that fork out of the flower pot now.) What types of materials are "kasherable". and which are not? Why? What is the status of glass? Plastic?Is there any difference between ancient materials and modern that may affect the halachic status? Do we need to be concerned about the utensils in a factory?A restaurant? At the home of a non Jewish friend? (Yes, I have many) Does a dairy plate touching a meat plate make it non Kosher? I will now begin a few posts on the theory of kosher utensils, then we can go to the practical issues involved in our homes. First of all, where does this concept begin?The origin is the Torah. Moses' final task is to avenge the treachery of the Midianites. The Israelites must fight. G-d commands the fighters to take home the spoils of war. But what to do about the non kosher utensils? We read in Numbers 31:22-23:
…22only the gold and the silver, the bronze, the iron, the tin and the lead, 23everything that can stand the fire, you shall pass through the fire, and it shall be clean, but it shall be purified with water for impurity. But whatever cannot stand the fire you shall pass through the water.
Most of this is clear. If a metal utensil has been used over the fire, it must be again put through the fire. According to the Talmud, it must be glowed white hot, so as to destroy any and all non kosher food molecules that have been absorbed. If it has been used with non kosher through boiling, it must again be boiled. The topic of "the water of impurity" has two possible meanings. Some say that any metal utensil acquired from a non Jew must first be immersed in a mikveh (extended by the rabbis to glass as well), while others interpret it to mean the purification water of the Red Heifer. According to this view, the immersion of utensils is rabbinic only. This was denounced in Christian Scripture: (Mark 7:4)
None of them will eat anything they buy in the market until it is washed. They also follow a lot of other teachings, such as washing cups, pitchers, and bowls.
The Talmud, however, makes several caveats. Earthenware (clay) is not Kasherable, as it is very porous and absorbent. The non kosher status of any utensil can only last for twenty four hours. You will recall the idea that non kosher food that imparts a bad taste will not make anything unkosher. How will food taste that has sat for a day inside metal? Nevertheless, a later rabbinic enactment forbade the use of a non kosher utensil even after twenty four hours, until kashered,lest we forget and use it within twenty four hours. However, if it was used after twenty four hours, the food will still be kosher! A few prominent rabbis have noted that there is a difference between the utensils then and now. Earthenware was untreated. Today's earthenware is almost like glass. Metal utensils used by the rich were generally fine. Those of the poor, were usually full of impurities,,and even holes! We read until fairly recently how a new metal utensil had to have flour cooked in it, in order to stop up the holes. Questions concerning Passover abound! Ancient utensils retained significant amounts of unwanted food. Modern utensils absorb in the neighborhood of a few parts per million, way below the halachic 1/60th. Some rabbis consider the neccesity of kashering to be today only a formality, while some materials (especially glass, and according to one prominent Israeli rabbi, stainless steel) as incapable of any absorption. The glass idea has existed since about the year 900, and is widely, but not universally, accepted. The stainless steel idea only came in two and a half years ago, and has yet to be widely accepted. Also, only heat will cause anything to be absorbed. If your non Jewish friend placed a cold pork chop on you kosher dairy dish, just rinse it off! How hot is hot, will be discussed in another post. But it will be an issue when we consider dishwashers. If only cold water is used, there is no problem to use them for both meat and milk, or even if a non kosher utensil was placed inside. If really hot water is used, that would mean a different story. This and more will be the topic of my next post.