With permanent ink a scribe has to be very careful TB Sotah 20

On today’s daf TB Sotah 20 Rabbi Meir who is a scribe adds iron sulfate to the ink he uses in order to make it permanent. The Gemara has two different traditions who told him not to use permanent ink. In the first go around his teacher Rabbi Yishmael instructs him not to make his ink permanent and in the second go around it is his teacher Rabbi Akiva. The Gemara is unable to resolve which version is correct.

Only in the first version do we learn the reason why the ink should not be permanent. “Afterward, when I came to learn Torah before Rabbi Yishmael, he said to me: My son, what is your vocation? I said to him: I am a scribe [lavlar] who writes Torah scrolls. He said to me: My son, be careful in your work, as your work is the work of Heaven, lest you omit a single letter from the Torah scroll or add a single letter, and in this you are found to be destroying the entire world if the mistake alters the meaning of the verse and results in blasphemy.” (Sefaria.org translation)

Rashi ד"ה אִם תַּחְסִיר אוֹת אַחַת provides us with two examples where a missing letter or an additional letter would change the meaning of the verse in a blasphemous way. If the scribe would leave off the letter “aleph” in the word “emet,” the verse will read “The Lord Adonai is dead- יהֹוָ֤ה אֱלֹהִים֙ מֶ֔ת” instead of “the Lord is truly God-יהֹוָ֤ה אֱלֹהִים֙ אֱמֶ֔ת.” (Jeremiah 10:10) If the scribe would add the letter “vov” to the word “bara,” the verse will read “Beraisheet created the Lord-בְּרֵאשִׁ֖ית בָּרָ֣אוֹ אֱלֹהִ֑ים” instead of “When Go begin to create” (Genesis 1:1)

Rabbi Ya’akov taught that Rabbi Meir made a distinction between the ink he used for writing Torahs, teffilin, and mezzuzot, and the ink he used to write the scroll for the sotah ceremony in the temple. “Rabbi Ya’akov says in the name of Rabbi Meir: It is except for the ink used to write the scroll with the sota passage used in the Temple.” (Sefaria.org translation) God’s name in the scroll used in the sotah ceremony needed to be dissolved in the bitter waters while we want the Torah scroll to remain kosher for as long as possible. If one letter is missing from the Torah scroll, it no longer remains valid to be read and needs to be fixed.