Mei-klaf and spray-klaf

I talked to someone who makes this kind of stuff.

He said that in the past mei-klaf were made from contact cement dissolved in a volatile solvent. The contact cement caused yellow stains on the klaf. Now, mei-klaf and spray-klaf are made by dissolving various types of rubber cement in a highly volatile solvent.

Anyone who ever used rubber cement knows that it is one of the worst possible adhesives around. Anything that sticks to dry rubber cement falls off after a while. Water-based ink is not compatible with rubber cement. That's why there are so many cases of the ink easily rubbing off.

A member of the אור לסופר  forum wrote:
אחד המתקנים (מביאים לו ס"ת אחרי הגהת מחשב) בירושלים אמר לי שהוא מיד יודע אם השתמשו במי קלף או לא
 לפי קלות המחיקה

The use of mei-klaf makes it much easier to erase the ink, which means that it reduces the adhesion strength of the ink to the klaf, which leads to early פסולים in the STAM.

We want to improve the adhesion of the ink to the klaf, not reduce the adhesion.

HaRav Kanievski Shlita was asked what is preferred, nice writing which can be easily damaged or not-so-nice writing which stays kosher longer?
His answer, in his own hand-writing:   That which stays.



  1. My policy has always been not to sell klaf mashuach(white coating) or klaf teimani(clear coating)due to the chatzitzah problem and also because they crack easily and its misleading to the consumer.

    A small amount of Mei klaf on the other hand was always deemed acceptable by those I have asked because it is not considered a chatzitzah, and if used properly does not cause premature cracking

    1. That was my basic understanding as well.

      A number of very big sofrim use Mei Klaf without hesitation, and they write for some big Gedolim. So I am not going to believe that it is a problem until I see written piskey halakha on it.

  2. The question of חציצה certainly needs to be dealt with by the Rabbanim. The most difficult part would probably be defining the limits. A 1 mm thick layer is definitely חציצה . A 1 molecule thick layer is definitely not חציצה . So where is the borderline? and how do we measure it?

    The question of damaging the adhesion strength of the ink to the klaf is, I think, much more serious. Too many cases have been publicized of ink rubbing off. R' Tzadok gave us one example. The sofer who checked 150 mezuzot at a bank and found the ink rubbing off is another example. And, there are many more. There is a famous sofer and teacher in Israel, his name is either אליהו כהן or יוסף כהן (don't remember) who wrote a few years ago that writing on mei-klaf always falls of faster than without mei-klaf. How many sofrim know what happens to their writing after a few years?

    In personal health and safety questions there is a hallachic limit of 1 in 1000. Not allowed to take an unnecessary risk if the risk is greater than 1 in 1000. The risk of writing on mei-klaf falling off is greater than 1 in 1000. Is it allowed? How about the Torah prohibition of לפני עור לא תתן מכשול ?

    1. Please produce a single written psak that says it is a chatzitza or even a problem.

      Especially as it does not meet the qualifications for being a chatzitzah, whereas chalk does.

      Leading sofrim say to use Mei Klaf, as do the poskim for the Mishmeret Stam, Mishmeret Sofrim, and Yad Rafael. So the typical way this sort of thing is handled in Judaism is that the dissenting opinion(that would be you) would produce a detailed psak and ask those other poskim to rule on it.

    2. Reb Michael, I think Zvi is more concerned about the adhesion problem than the chatzitzah problem.

      My view:

      1) I was def. told it is not a chatzitzah because it is absorbed into the klaf rather than sitting as a barrier like mashuach and temani. This makes sense.

      2)Re adhesion, my understanding is that if used properly it should not reduce the life of the writing. I guess "used properly" means not using too much.

      I'm not a klaf expert but sometimes too much mei klaf causes the ink to sit on top of the klaf rather than get absorbed into it, which will case the ink to crack easily, particularly tefillin shel rosh parshiyos that are bent

  3. just trying to get a better understanding of the subject rabbi kadosh mentioned something abought that if the ink can go around it there is no problem i wanted to know if this in adition to the fact that it has to be for the purpose of the klaf or not my real question is benogeh to little fibers on the klaf i think everyone has them (at least i do and they are verry hard to take off especially during writing


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