Gold Tefilin

The mishna in Megillah says that if you cover your tefillin with gold it is posul. I always thought that it meant that you put a layer of gold over your batim. I just saw that although the Tur holds it means you painted it gold, Rashi and the Ran hold it means you made gold batim. This is nogeia to the question whether you can paint your tefilin with black paint or dye. The Chayei Adam in the Nishmas Adam Klal 14 has a machlokes with his rebbi the Noda B'Yehuda. The Noda B'Yehuda (Siman 1) writes that Rashi and the Ran is a rayah that you can put a black paint on your tefillin. The only problem with gold tefillin is when the batim are gold, but not when the batim are leather and you paint it gold.

The Nishmas Adam argues and says that the Tur is against this. Plus there is a separate issue that the tefillin have to "see" the air and can't be covered. Putting on a black paint that can't be scraped off is a problem. Also, even if it can be scraped off, the Nishmas Adam feels it is a problem. The Nishmas Adam at the end writes that he sent his teshuva to the Beis Meir who agreed with a lot of what he wrote and the Beis Meir also told him that Rabbi Akiva Eiger also held similarly.