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<DIV><FONT face=Calibri>Are there any chemists on Avodah? In the daf, 54a, the
gemara brings a Tani Levi that describes the construction of the Misbeach.
It was concrete-like in nature. It used forms much as we would today,
aggregate of perfectly smooth stones (not to be felt when passing a
fingernail over them) and some sort of matrix or "mortar" composed of some sort
of mixture of sid, kunya and zefes, commonly translated as plaster or
lime, lead, and pitch or bitumen. My question is about this "mortar" they
used. I did a bit of a search to see if anything turned up about such a
combination - nothing did. There was some sort of use for lime and asphalt at <A
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Hydrated Lime to Hot Mix Asphalt,</H2>
<DIV><FONT color=#000000 size=3 face=Calibri>but I doubt this relates to nidan
didan. Can anyone explain how they used this mixture in forming the cement and
how this functioned chemically? Do we have any modern equivalent? Part of what
bothers me, is the high temperature (621.5 F) required to keep the lead
molten? How to keep it from solidifying before being poured over such a large
area in the neighborhood of 60 ft squared? Was it perhaps some chemical compound
that included pb as a component (but without exhibiting a high melting
point) and some of the resins extracted from the bitumen together with the
lime?</FONT></DIV>
<DIV><FONT color=#000000 size=3 face=Calibri></FONT> </DIV>
<DIV><FONT color=#000000 size=3 face=Calibri>Can anyone enlighten
me?</FONT></DIV>
<DIV><FONT color=#000000 size=3 face=Calibri></FONT> </DIV>
<DIV><FONT color=#000000 size=3 face=Calibri>BTW, I think there is a discussion
about whether it is iron or metal that is under prohibition of use for
the mizbeach. But apparently lead was OK as a component of the mizbeach? Perhaps
the lead only enters the "mortar" as an unrecognizable component of a
compound (if not just iron is under prohibition) with its own set of
physical properties?</FONT></DIV>
<DIV><FONT color=#000000 size=3 face=Calibri></FONT> </DIV>
<DIV><FONT color=#000000 size=3 face=Calibri>Also does the fingernail rule only
apply to the individual stone aggregate, or to the entire surface after removal
of the form. If so, the aggregate-mortar joints must have been near perfect -
almost like a polished surface!? Also does this fingernail rule apply to stone
aggregate buried in the interior of the mizbeach and never visible at its
surface? If yes - you will never know whether during construction a stone in the
interior became scratched and made the mizbeach pasul!</FONT></DIV>
<DIV><FONT color=#000000 size=3 face=Calibri></FONT> </DIV>
<DIV><FONT color=#000000 size=3 face=Calibri>Kol Tuv</FONT></DIV>
<DIV><FONT color=#000000 size=3 face=Calibri></FONT> </DIV>
<DIV><FONT color=#000000 size=3 face=Calibri>Chaim Manaster</FONT></DIV>
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