Does clay used as a foundation count as clay or as the ground?

Question

The mishnah in Keilim 6:1 describes a stove made in two ways: a pot resting on three metal^* pegs that are either (1) attached at the ground via clay, or (2) stuck into the ground. In the first case, the clay gives the stove the status of a "clay stove", which is susceptible to tumah, whereas in the second case, there is no susceptibility to tumah.

‮העושה שלושה פטפוטין בארץ, וחיברן בטיט להיות שופת עליהן את הקדירה: טמאה. קבע שלושה מסמרין בארץ להיות שופת עליהן את הקדירה: אף על פי שעשה בראשן מקום שתהא הקדירה יושבת, טהורה.

If he put three props into the ground and joined them [to the ground] with clay so that a pot could be set on them, [the structure] is susceptible to impurity. If he set three nails in the ground so that a pot could be set on them, even though a place was made on the top for the pot to rest, [the structure] is not susceptible to impurity. (translation from Sefaria)

Imagine a case where you create a clay foundation, strengthening the ground with clay (and leaving the clay flush with the ground). What would be the rule when pegs are stuck into such a clay foundation? Would it be considered as attached to the ground (and hence not susceptible to tumah) or as attached via clay to the ground (and hence susceptible)?

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See also this question.

^* I know that some commentaries read the initial sentence as referring to clay props, but I'm asking according to those who don't (or according to everyone, if the material doesn't matter). See also the tosefta Keilim BK 5:1 which seems to support a read of metal props.

Answer 1

I assume you are asking according to the Tana Kama of the Tosefta.

See the Rash regarding the commentary you addressed, that the pieces are attachet on their bottom and not on their top. He begins his explanation quoting a Tosefta.

עשה ג' רגלים בארץ ומלמעלה בראשם חיבר שלשתם בטיט שנעשו כעין כלי ברזל שקורין טרפי"ד להושיב הקדרה עליהם ועושין אש תחתיה אי נמי יש לפרש שחברם בארץ בטיט טמאה דנעשה ככירה לטמאות באויר כנגד גובה הפטפוטים:‏

According to the commentary that the props are attached to the ground via clay, they became a Kira, a terracotta utensil, susceptible to impurity by its inner space

קבע. שנעץ שלשה מסמרין בארץ כנועץ יתד אע"פ שתקנן בראשן הרחיבה שלא יהו חדים ושיפן יפה שלא יקלקלו את הקדרה היושבת עליהן טהורה. לפי שנעשו לקדירה תחת כירה נקט טהורה לשון נקבה

The props are stuck into the ground as one plant a stake and they are blunt and flattened on their top.

ומצי לפרש דטהורים לגמרי דאין להם תורת כלי כיון דכל אחד לחודיה לא חזי ואינן מחוברין זה לזה

It's possible to explain that the nails are not utensil at all, no more nails because they are not sharp, and not a new utensil because they are separate pieces.

ואם באנו לפרש טהורים מדין כלי חרס צריך לפרש דאע"פ שעשה בראשן היינו שהדביק בטיט בראש כל אחד ואחד שתהא הקדרה יושבת טהורה היינו דוקא בלא חברן בטיט בראשן

If we explain that the nails are clean from the specific susceptibility of terracotta utensils to be unclean from their inner space, each of them is consolidated on its top by a ball of clay. Their is on the top three surfaces of clay to put a pot on them.

ולאידך לישנא שלא חברן לקרקע בטיט כדמוכח בתוספתא.‏

And according to the explanation that they are entirely not susceptible to be unclean, they have no clay their tops. We have the proof in the Tosefta that the nails we are talking about in our Mishna are not attached by clay.

תניא בתוספתא (רפ"ה) שלשה מסמרים ג' יתידות ג' פטפוטים שנתנם בארץ וחיברן בטיט להיות שופת עליהן הקדרה טמאה

In Tosefta it's written that the nails are attached by clay

רבי יהודה מטהר עד שיחבר זה לזה בטיט.‏

Rabbi Yehuda says that they need to be attached each to other by clay

ומודה רבי יהודה שאם נתנם על גבי האבן וחברם לה שהיא טמאה מפני שהאבן מחברתן

But Rabbi Yehuda agrees in some cases they are not attached each to other by clay, but are stuck into a stone, the assembling object is susceptible to be unclean

פירוש וחברם בטיט בראשם כדמפרש במתניתין

The Tana kama addresses that each of them is consolidated on its top by a ball of clay

ולאידך לישנא דפירש שחיברן בארץ בטיט

But according the explanation of the Mishna that they are not susceptible to be unclean at all, the nails of the Tosefta are attached to the ground on their bottom

ולכך מסמרים דהכא טמאה ודמתניתין שלא חיברן בטיט טהורה

So, we understand the difference between the Tosefta and the Mishna. In Mishna the nails are not attached by clay, but in Tosefta they are attached by clay

ורבי יהודה מטהר נמי הכא אע"פ שחיברן בראשן כיון דלמטה לא חיברן.‏

The Rash comes back to the explanation that they are not susceptible to be unclean by the specific uncleanness of utensils of terracotta. Rabbi Yehuda needs an attachment each to other on the bottom

ולאידך לישנא דאע"פ שחיברן לארץ כיון שלא חיברן זה לזה דמה שהארץ מחברת מלמטה לא חשיב חיבור שאם בא לטלטלן במקום אחר מתנתק חבורם:‏

But according to the explanation that they are not susceptible to be unclean at all, Rabbi Yehuda holds that the separate attachment to the ground by clay are not suficient to make them an utensil (this is my understanding of the Rash, but the Boaz explains it differently). (personal note. Tana Kama holds that stuck to the ground by clay is better than stuck into the ground, it's the difference between the case of the Tosefta and the case of the Mishna)

אבל נתנם על גבי האבן וחברם לה חשיב חיבור הואיל והאבן מחברתן שהיא מטלטלת ביחד עמהן שחיברן זו לזו בטיט בראשן.‏

The Rash comes back to the explanation that we discuss about the susceptibility to be unclean by the specific uncleanness of utensils of terracotta. But if he put the nails on the stone and attach them to it, they are attached each to other because the stone is movable together with the nails. The stone attaches them each to another. They have balls of terracotta on their top and on the bottom they are attached each to other and they are an utensil of terracotta

ולאידך לישנא דפירש שחיברן בארץ בטיט

According to the explanation that we discuss the absolute susceptibility to be unclean, Rabbi Yehuda needs that they need to be attached one to other by clay and Tana Kama they can be attached to the ground independently one from other.

There is indeed a difference between a nail stuck into the ground and a nail stuck by clay on the ground. The second is stronger. Cementing on the ground is stronger. Maybe that when using it is warm and the clay become very strong.