Dear Frank,
I am fully with your assertion that...
> Lime mortar is a material of importance
> to diallists.
It is magic stuff but many builders today
do not appreciate it or even know how to
use it.
I have one micro-quibble with one of your
comments...
> For repairs and pointing to stone dials
> lime mortar, which is flexible, should
> always be preferred to cement. (Cement
> is to be preferred for brickwork)
If you have a listed brick building where
lime mortar was used, you will get into
big trouble with local area conservation
officers if you use cement!
As a simple rule:
If lime mortar was used originally
then lime mortar must be used for
any repairs.
This applies to stonework, brickwork
and plasterwork.
If your old sundial is mounted on dodgy
brickwork, then use lime mortar to fix
the brickwork.
Lime mortar is not actually flexible but
it can behave slightly as if it is...
With cement, if you bend it you will
get a crack.
With lime mortar, if you bend it you
get lots of tiny cracks which, over
time, will anneal by chemical reaction.
You are right that lime mortar has been
used since antiquity. The Romans used
hydraulic lime mortar for repairs to their
aqueducts since it will set under water.
Alas, I cannot give the details of the
chemistry but I look forward to hearing
from someone who can.
About half a century ago, for a few days
one very hot August, I worked for a master
brick-layer. Since I knew nothing at all,
he made me mix some lime mortar as my
first task. I diligently did as I was
told and he was quite pleased.
I then asked when we were going to use it.
"Sometime after Christmas", he replied.
That's how it is with lime mortar.
Very best wishes
Frank
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