Irreversible. A question has come up on BP that may have been meant in the
following sense: if we are preservationists then how can anything done to an
historic building be irreversible? I think it important that the terms of
fixing old buildings be readily apparant. Again, a need to clarify definitions
of the words we use.

First off, I take preservation to imply keeping something from being damaged
and/or destroyed. Restoration to imply putting back that which is gone.

The other concept we need here is *historic fabric*.

When you destroy an old brick that is no longer manufactured then you cannot
put back the same or matching brick once again, you have to do something else.
Find another brick? Salvage existing brick? Steal brick from another part of
the building? Possibly make a new brick, but the chemical composition of the
clay differs (where was the clay for the original brick mined?), the
durability, appearance and performance characteristics of the new brick will
differ from the original. A short run of a historically manufactured brick is
economically untenable, the manufacturer processes have changed, in some
respects the manufacturing knowledge has not been preserved. In this case the
historic fabric has been irreversibly removed.

This may seem picky. It all depends on how much we value the historic fabric.
On a warehouse in Brooklyn the owner is apt to not care too much what brick is
used to replace the old brick. On a project we are doing at a local University
we removed the old brick that we were told we could not salvage due to
engineering considerations. The size, composition, and appearance of the brick
makes it unavailable from any contemporary manufacturer. Finding matching
brick can be an extremely difficult problem -- for the most part, those who
have simple solutions have probably never tried to really match an historic
brick. In NYC you have a lot of different types of historic brick. What we
have come to, with this one project, is using a blank brick (neutral color),
cutting it to size, and applying a glaze to the surface to replicate the
appearance of the original Roman iron-spot brick. This results in a 2,400%
increase in cost per brick over common brick that would be used on a
warehouse.

][<en Follett