Rabbi Yohanan also said: Rather drink a cupful of witchcraft than a cupful of lukewarm water; that is so only if it is in a metal vessel, but in an earthenware vessel it does no harm. Moreover, even in a metal vessel we say it is harmful only if no spice roots were thrown into it, but if some spice roots were thrown into it, it does no harm. Moreover, even if no spice roots were thrown into it we say it is harmful only if the water had not been boiled, but once it had boiled it can do no harm.
We are aware of danger in lukewarm water inasmuch as the low-level heat encourages the development of bacteria. Two opposite processes would protect from this development:
– freezing, which limits oxidation and decay
– severe heat, which destroys microscopic organisms.
Leaving different types of drinks in metal containers also poses a variety of risks that are connected with chemical reactions (e.g. rust) between the metal and substances in the drink.
Rabbi Yohanan also said: If a person is left a fortuneby his parents and wishes to dissipate it, let him wear linen garments, use glassware, and engage workmen and not be with them. ‘Let him wear linen garments, especially of Roman linen;‘use glassware,’ especially white glass;‘and engage workmen and not be with them,’ especially to work with oxen, which can cause much damage.
In all likelihood, what is referred to as “white glass” is actually transparent glass, which is much more difficult to make than ordinary colored glass. To make transparent glass, the purest raw materials need to be prepared. During Talmudic times, such glass was rare and expensive. Usually utensils made from such glass were also more delicate, and thus, more breakable.