In a message dated 11/29/05 6:59:42 AM Eastern Standard Time,
[log in to unmask] writes:
Anybody got any guidance for me on how to choose  between mortar that looks
too light, as opposed to mortar that doesn't match the  (interior) sample but
looks right?  I am scared to death to call for the  pale yellow mortar and have
the building wind up looking like there are neon  lights in the mortar
joints, but that seems to be what the mortar samples  show.


Ralph:

Ah, free guidance you want?  Sure.  Do what you  damn well please.  You are
the Architect.  If you don't want neon go  with Inca-decadent lights and claim
that you were designing for the hacienda  crowd.

Technical note:  The color change is probably due to  oxidation of Fe2 to Fe3
in some component in the cement phase in the  mortar, but might alternatively
be due to deposition of organic matter  in the exterior portion of the joint
or to simple carbonation of the hydrated  lime in the mortar.  To determine
what happened, have two petrographic  analyses done; one of an interior sample
and one across the exterior.

Steve Stokowski
Stone Products Consultants
Building Products  Microscopy
10 Clark St., Ste. A
Ashland, Mass. 01721-2145
508-881-6364  (ph. & fax)
http://members.aol.com/crushstone/petro.htm

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