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Hilchos Tefillin 32 (page 86)
מאמצע סעיף ט וכן נוהגין עד סעיף יג 

Using Machines to Tan Klaf
Necessary Precautions When a Goy Prepares the Klaf
Using Klaf from an Animal that is Prohibited to Eat


Using machines to tan klaf

All stages of the processing from the lime bath onward must be done lishma. Some poskim hold that if the initial stages were performed lishma, all subsequent stages are considered lishma. Accordingly, if one stage was done lishma, whatever stages come after it can be performed by machine if the machine is started lishma. Other poskim permit machines if all the significant parts of the process are performed lishma. It is best for the entire process to be performed by Jews operating lishma.

(ס"ק ל, וביה"ל ד"ה להרמב"ם; ביאורים ומוספים דרשו, 50)



Necessary precautions when a goy prepares the klaf

If a goy has access to the hides during tanning (e.g. a goy is working on non-essential parts of the process), he could possibly switch the kosher hides with non-kosher ones. Therefore, the hides being processed lishma should be marked with a sign that the goy cannot reproduce. Bedieved, it is permissible to be lenient in a case where the goy thinks that the Jews will notice if anything is exchanged. If a goy applies patches to torn hides, there must be supervision to verify that only kosher hides are being used to create the patches.

(סעיף י, ס"ק לא, וביה"ל ד"ה כעין וד"ה לזייף)



Using klaf from an animal that is prohibited to eat

Only the skins of kosher animals may be used for klaf. The skins of kosher animals that died or are otherwise forbidden to eat may be used. There are poskim who hold that the ideal hide for stam should come from the skin of an embryo which was found in the womb of an animal after slaughter (and does not require its own shechita). Since it was never born, it is not possible that it was ever used for an aveira. The skins of fish should not be used because they are slimy.

(סעיף יב וביה"ל ד"ה יהיה וד"ה ואפילו; ביאורים ומוספים דרשו, 51)





  • It is proper to declare the intention of lishma when tanning the skins for stam. Bedieved, an unspoken intention is also valid.
  • Klaf prepared for a sefer Torah may be used for tefillin and mezuzah. Klaf prepared for tefillin may be used for a mezuzah, but not a sefer Torah. Klaf prepared for mezuzah cannot be used for either tefillin or sefer Torah, both of which have greater kedusha.
  • According to the Rambam and Tosofos, a goy cannot participate in making klaf for stam. According to the Rosh, a goy may assist in making the klaf if he is supervised and reminded about lishma by a Yid.






  • Understanding the concept of mukaf gevil

  • The size and location of a disqualifying hole

  • A hole in the interior of a letter