Have just had a pointing mortar from a NYC mid-C19 manufacturing loft 
building analysed. I thought it might be lime putty pigmented with brick dust. 
Turns out to be chalk (+/-90%), an organic binder, probably animal glue (+/- 
5%) and a red mineral pigment, likely red ochre, and traces of silaca dust.  
Like a distemper paint but very heavy on the solids.

It was used in the brownstone section of the facade, where the joints were 
fine. The brownstone arrises were in very good shape. Much of the mortar was 
firmly in place, although it was easy to scrape out, as crumbs. I did not 
investigate the bedding mortar which was about an inch back and clearly 
harder and not pigmented, as one would expect.

Am interested to know whether any of you have come across this mix and 
have tried to imitate it. It would be very breathable and has a good bright 
color.

Christopher Tavener

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