Even if your Mezuzah is written properly and according to Halacha, being that it is a very delicate item it needs to be treated gently and cared for properly. It may seem obvious, but many people are unaware of the issues at hand.
1) When cleaning a Mezuzah’s outer case it can be lightly dusted. But never use liquid cleaners because they may seep within the case and damage the parchment scroll.
2) As well I have seen many burnt and water-logged Mezuzos.
If your Mezuzah is going placed out doors and will be exposed to the rain and moisture, be sure to put it in a waterproof cover. A water proof cover is a solid piece of plastic with only one opening on the bottom and it is sealed airtight with a rubber cork. If it will be in contact with the sun be sure it is in a white or brightly colored case which will reflect the sun as opposed to a dark color attracting it, thereby burning or drying out your Mezuzah, which causes the letters to crack and very often renders it Possul / invalid.
As well it is important to avoid metal covers, the reason for this is two fold 1) The Das Kedoshim writes as follows; The reward for fulfilling the Mitzvah of Mezuzah is long life as the Posuk says “Leman Yirbu Yimeichem” and weapons of war are made from Barzel – Metal therefore it’s not proper to put a Mezuzah in a material that cuts life short. 2) Metal tends to absorb the temperature much more than plastic, in the winter it becomes ice-cold and in the summer it gets scalding hot,which is very damaging for a Mezuzah.
(think about it would you touch a metal railing during the winter months without gloves? or a metal railing in the heat of a summer day? I think not! )
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Many things can render Tefillin or Mezuzah not Kosher or at best minimally Kosher.
Some of these happen over time with aging and some unfortunately are Posul from the get go.
Letters, words and or Tagim that are missing, extra substituted, touching, Broken, Improperly Spaced, misshapen faded, cracked and weather damaged.
We document the problems we find and periodically upload them to the website.
We hope that this will educate and encourage the public to purchase only Tefillin and Mezuzas that are high quality from a reputable source, to take care of them properly and have them checked regularly.
Rabbi Kass was ordained by Rabbi Yisrael Meir Lau, former Ashkenazik Chief Rabbi of Israel. He is certified as a Sofer for both Kesivah and Hagoah by one of the leading experts in Safrus, Rabbi Avrohom Tzvi Vosner, Rav of the Vad Mishmeres Sta”m.