I know about two composite materials -- particle board and composite leather. Each is made of small bits of the original mixed with filler/binder. In halacha, there are times when wood and leather are named as specific needs:

  1. A wood casket when burying someone (if one uses a casket, and one subscribes to the currently accepted practice)

  2. A prohibition against leather shoes on Y"K and T"B'av (ignoring for the moment all the opinions that argue on this)

Would these laws apply to the composite version of wood and leather? Each is made of the original but is not identical with the original.

n.b. there might be other composites which could stand in for materials listed in halacha - this is not meant to be an exhaustive list, just the ones I have come across recently.

  • There was a debate among the poskim regarding gluing pieces of leather together, and forming a "bayis" for tefillin. Likewise, could a leather based glue be used to fill in crucial holes in "bayis" of tefillin? – IsraelReader Jul 23 '18 at 11:03
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    Can a hole in a "shofar" be filled with a glue based on ground "shofar" powder? – IsraelReader Jul 23 '18 at 11:24
  • note that composites may differ; if it's primarily glue and minority leather may be considered different to the other way round – user15253 Jul 23 '18 at 11:31
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    Just ask if they can accept Tumah. – Double AA Jul 23 '18 at 11:37
  • @rosends There has been a major discussion concerning garments made of "mixed fiber fabrics" in regard to shatnez. – RibbisRabbiAndMore Jul 23 '18 at 13:55

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