Re:Late response to Michael Tolan's response to David Wests
inquiry              about hacking back of sandstone at Cooper Union.



"Hacking back" is a harsh term but sounds like Aussie slang!

During a 3 month mock-up period, different techniques of honing and
tooling were tried to achieve a satisfying visual appearence for a
surface wich had been truly "hacked up" during a prior "restoration"
campaign. It looked like someone scored the stone with chisels for the
purpose of applying a cement coating, then ran out of cash for the
cement.

A tricky situation, esthetics being just one of the problems. The
earlier "hacking" left the surface rough and friable. The building skin
was open to moisture penetration. Stone was flaking off one peoples
heads.

It was thought to hone the stone to a perfectly flat surface, one
matching the original honed surface. The existence of ferrous anchors on
every ashlar stone made it unwise to remove to much stone, exposing the
anchors to moisture penetration and possible expantion.

The honing technique was an all or nothing proposition. As the stone was
extremely pitted and scarred, lite honing exagerated the appearence of
the pitting. Through many trials and removal of scaffold to view the
mock-up section from street level, it was decided that a light tooling
with pneumatic toothed chisels delivered the appropriate surface. This
method created the illusion of a smooth and true surface and  tightened
the building skin, without compromising the ferrous anchors below. We
all know what happens when ferrous anchors are compromised.

Nicholson Galloway Contractor, Michael Tolan, Project Forman, provided
valuable in put to this process. They devised a method of water fed lite
honing with diamond abrasives. This performed prior to tooling, helped
reduce the time spent in hand tooling considerably.

Respectfully,

N. Micros