Torah, Science & Kashrus in the Classroom

By: Rabbi Dovid Heber

Spring 2025

Over the years, I have been invited on multiple occasions to speak at various girls’ high schools in Lakewood about the impact of astronomy on the Jewish calendar and halachic zmanim. The inherent message I have aimed to give over is that one needs a basic understanding of math and science to fully comprehend certain halachic issues.

For example, the earth’s rotation on its axis is the basis of zmanei hayom (halachic times of the day) that are so much a part of our lives with regard to davening times and knowing when Shabbos and Yom Tov begin and end. One needs to know how the moon rotates around the earth to better understand Rosh Chodesh and the Jewish calendar. Indeed, Chazal had keen insights into scientific topics that were discovered hundreds of years later by researchers.

Investigating how a product is manufactured and analyzing the composition of the raw materials […]

Vinegar: Doing Kashrus Tastefully

By: Rabbi Tzvi Rosen

Spring 2025

Vinegar has a long and storied history and plays a highly-prized role in every aspect of modern life – whether as a nutrient, flavorant, preservative or household cleanser. The name vinegar is derived from the French “vin aigre, which literally means sour wine. According to legend, its discovery is credited to a neglected barrel of wine that had been left in storage and allowed to ferment and become sour.

We find several references to vinegar in both Tanach and the Gemara. A nazir is forbidden to consume anything derived from grapes, which includes wine vinegar;[1] Dovid Hamelech accuses his tormentors metaphorically of giving him vinegar to quench his thirst;[2] Boaz’s workers dip their bread in vinegar;[3] and Mar Ukva refers to himself as “Chometz ben Yayin” – Vinegar, the son of Wine – when comparing himself to his father’s degree of piety.[4]

Vinegar […]

Tevila Exemption for Appliances with Electronic Components

By: Rabbi Zvi Holland

Spring 2025

For many years, Rav Moshe Heinemann shlit”a instructed STAR-K to advise consumers that electric appliances which require tevila – such as toasters, waffle makers and hot water kettles – can be toveled and left to dry for three days. I have given this advice probably thousands of times and never once had a call back that the appliance was ruined.

There are, however, appliances that have both electric and electronic components. Electric devices convert electrical energy into other forms of energy, while electronic devices control the flow of electrons to perform tasks. Once exposed to water, damage to electronics begins within seconds – and the longer the exposure, the worse the damage.

Printed circuit boards consist of a laminate containing fiberglass and copper-clad epoxy, which forms the circuit’s wiring. This creates the perfect environment for galvanic or two-metal corrosion. Water contains minerals such as calcium, magnesium, potassium and salt, which accelerate […]

The Mitzvah of Tevilas Keilim

By: Rabbi Moshe Heinemann

Spring 2025

We are an Am Kadosh, a Holy People, who are mandated by Hashem to imbue all aspects of our lives with holiness. We elevate even the mundane activity of eating and vest it with special kedusha (sanctity): the food on our plates must be kosher and the table on which we eat is likened to the holy mizbe’ach. The plates themselves, and all keilim (vessels and utensils) used to prepare our food, must likewise be infused with kedusha.

Just as an aino Yehudi must tovel in a mikvah in order to become Jewish, so too must keilim acquired from an aino Yehudi undergo tevila in a mikvah before being used by a Jew. This is the mitzva of tevilas keilim.

If a kli requires tevila, it may not be used even once before it is toveled. If a kli was used numerous times without tevila, one is still required to immerse […]