Thought for the Day: What Temperature Is Needed for ליבון חמור? Getting Some Modern Help to Understand Ancient Wisdom
As you may know, Pesach is less than 30 days away. You know that either because (1) we are past Purim and Pesach is always 30 days after Purim, or (2) the most oft-heard phrase in your home is, "Aaaagh!!! Pesach is less than a month away!!! Aaaagh!!" (Number of exclamation points is based on estimates by someone who no longer has children at home. Your level of stress and urgency may vary.)
You would think that the oven, which has been filled with hot chameitz all year and now needs to be a completely chametz-free zone, would be a huge stress point. Nope. Preparing the oven nowadays is an eerily calm island in a sea of frustration. That is because the very same heat that created the problem can now be used to solve it. The basic rule is the way the chameitz went in is how we take it out. Of course, since it is Pesach, we are way stringent. Besides that, we like to destroy the chameitz instead of just removing it (which has its own disposal and contamination issues; not our topic). So the heat of the oven is our best friend.
There are two basic techniques of incineration: (1) ליבון קל/moderate incineration and (2) ליבון חמור/intense incineration. In practice, ליבון קל means to turn the oven on to its highest setting for an hour or so. Most modern ovens have a self-cleaning cycle, and the modern-day poskim say that is sufficient for ליבון חמור. Of course, these terms come from Chazal, who did not have our modern kitchen appliances. Nor did they use the same temperature scales. (Based on search with Gemini, the idea of temperature as a physically measurable quantity as well as both the Fahrenheit and Celsius scales go back to the mid-1700s.) Chazal used terms to describe the different levels of incineration using easily observed physical processes. ליבון קל/moderate incineration means hot enough to ignite straw (that is, if you touched straw to the oven's surface, the straw would catch fire). ליבון חמור/intense incineration, on the other hand, means hot enough to make sparks fly.
Setting straw on fire seems pretty easy. I set plenty of things on fire with just a magnifying glass. I looked it up using Gemini (that is Google's AI tool... my go-to) and found that the temperature needed to set straw afire is 500°F to 550°F. Cool! Pretty much the highest temperature to which our household ovens can be set.
How about getting those sparks to fly? This is what really got me interests. I know the poskim say that the self-cleaning cycle, which gets to about 900°F, is good for ליבון חמור, and I have used the self-cleaning cycle on my oven... but I have never seen sparks flying. I asked around (of course I did), and only one person I asked has seen sparks flying... but not from a self-cleaning oven. He actually kashers liver on a grate over hot coals. In that case, you can get sparks flying off the metal. But not in a self-cleaning oven. (I also know of a kollel guy who decided that ליבון חמור means ליבון חמור, darn it! So he went and rented a blowtorch to get the oven to the requisite temperature. He melted away the bottom of his oven. I heard this story directly from his wife, who was quite pleased with her brand-new oven for Pesach.)
One of the people I asked was R' Schwimmer, shlita, about the sparks. R' Schwimmer told me that he had some notes that said it was the temperature at which sparks would be produced when hitting the hot metal with a hammer. Interesting... That would explain why I and others haven't seen sparks; the oven door actually locks when self-cleaning mode is started, so I couldn't really bang on the inside of the oven to check even if I wanted to. (Would I, though? See story at end of previous paragraph. I was not the protagonist, but I might have been had I not heard that story from his rebbetzin.)
No problem! I went back to Gemini to ask, "In the case of a blacksmith hitting hot metal with a hammer, how hot does the metal need to be in order that sparks will fly off when he hits the metal?" The answer started with:
To get those cinematic sparks flying in a blacksmith shop, your aren't just looking for "hot" -- you're looking for a specific physical threshold where the iron literally begins to burn or break apart at the surface...
Cool! Indeed, that is my quest. The answer: 2,000°F to 2,400°F! Yikes!!! Way too hot!
At this point, we have a few options:
- According to science, sparks are not produced by pounding on hot steel that is only heated to 900°F, the temperature of the self-cleaning cycle in our ovens. I guess the expression ניצוצות ניתזין הימנו/sparks will fly off it is just poetic.
- Nature has changed. Sparks used to be produced at 900°F, but now it needs to get to at least 2,000°F. Cool.
- More investigation is needed. I am missing something...
Ok, so I reject (1) with both hands! No, no, no. We would never contradict Torah with modern science, but we also can't ignore scientific data. Data is real. Halacha is real. It is imperative to understand all data from a Torah/halachic standpoint. While (2) is possible—and even mentioned in other areas—it would be hard to say that here. We certainly know that the nature of steel has not changed over the last few centuries, so that doesn't seem to help here.
That leaves us with (3). There is some disconnect; we just need to find it. You might think that this is where AI comes in handy. Nope; not yet. There is an old expression that began with the computer age—which began the same year that I was born, 1957 CE, interestingly enough—that goes, "Garbage in, garbage out," aka GIGO. It came about because computers produce results quickly. But getting results quickly is not good enough; you need good results quickly. If you feed in garbage, you get garbage out. Regarding AI, woefully underspecific queries are just garbage input. With AI, not only do you get garbage out, you get sophisticated garbage out.
Before we go back to AI, we need to think. What, in fact, has changed over the last few hundred years regarding steel? It turns out that steel—a harder and more durable form of iron—has been around for nearly 4000 (yes, you read that right, and yes, I just learned that writing this TftD) years. Refined steel, though, is only about 300 years old. Cool, now we need some data. Let's ask Gemini about the nature of steel/iron in the middle ages and blacksmithing with that less refined steel.
I won't bore you with the details, but here's a high-level summary: There is a thing called "mill scale," which is iron oxide. That forms on the outside of the steel and is brittle. Hot enough, and the metal is soft enough to bend under the brittle mill scale, sending the scale flying off. Still need more than 1,000°F for that. However, in a dimly lit 17th century forge, 930°F looks like a clear red glow. Friction from the hammer can lower that to 850°F. Some impurities, such as silicate slag, hold their redness a bit longer than pure iron. Put that all together, and it is not hard to understand why the self-cleaning cycle in our ovens fits the criteria given by Chazal and as explained by our poskim through the ages for ליבון חמור.
Literally minutes after I finished my analysis and research, R' Schwimmwer gave me a printout of his notes from his rebbie, R' Shaul Katz, shlita. There it was, in footnote (עב):
Indeed, in the sefer מעדני אשר it is written that I heard from R' Levi Yitzchak Halprin that perhaps the intent in the description ניצוצות ניתזין הימנו for the temperature needed, it is refering to attached קליפות/scales that are attached so tightly that they cannot be washed off, but only can be removed by fire, though the precise temperature is difficult to assess...
Isn't that cool? This was not trying to force the straight peg of Chazal's expression into our crooked holes of understanding. This was working out how to express Chazal's precise language in terms that we could better understand. Also, we were trying to understand a p'sak halacha, not create one. In the end, we were even able to see the fulfillment of Chazal's statement that when one looks earnestly and sincerely, he will find.
I asked Gemini how to end this. I really like the result:
Afeard-no-more: (A bit poetic/archaic).
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