In a message dated 5/31/01 7:07:15 PM, [log in to unmask] writes:

>Looks like I have a deep red lime pointing mortar with brick dust on a
>
>restoration job, and am thinking about replicating the original, hoping
>that
>
>the original color can be largely recreated through the brick dust and
>that
>
>the dust would add to the setting properties of the mortar. But before
>I go
>
>too far down this track, does anyone know of a US source of brick dusts?
>
>The color appears somewhat darker than any of the bricks that might be
>
>salvaged from the building.  I have a source in England but transporting
>
>brick dust across the Atlantic seem a little farfetched, as it were. Any
>
>comments, helpful if possible ?
>
>

Just an opinion of course, but likely it is not brick dust you are seeing.  I
think the amount of brick dust that would be required to tint a mortar a
"deep red" would be prodigious.  I have put as much as 5-10% (by volume) of
brick dust into lime mortars in an attempt to recreate the "red" fines that
were left (in the original mortar samples that we were trying to mimic) after
digestive testing, and there was very little observable effect on the color
of the mortar.  I would suggest that, depending on the period of the masonry
etc, that what you are seeing is iron oxide or something similar fines that
were added as a tint.  We are finding what we believe to be iron oxides in
some decorative concretes that we are looking at for the Smithsonian.
Contact me off-list if you would like info on where we are looking for what
we hope are appropriate iron oxide colorants, etc.

 BTW as to the setting properties that brick dust might add, I would suggest
that they would be minimal as well.  Modern shale brick, and I am making an
assumption that is what you are using, are fired much hotter and are much
harder than oldy-timey clay bricks.  The dust just ain't the same.  However,
if you are lucky enough to get hold of some old bricks that someone is
willing to let you grind into dust, have at it...but then there is also the
question of the type of lime you are using.  Granted, you can make lime putty
from modern hydrated lime, but it ain't the same as traditional lime putty
either.  I have found that if you make the putty from hydrated lime, it takes
4-5 months of aging for the stuff to get even close to having the same
qualities as wood-fired lime.  Again, just an opinion.

Mark