Leland; The Gommage system was used quite a bit at Yale and I think there is a
crew going there in the Spring. We also did alot of testing at New Haven  City
Hall; and TH was a sub to the Coatings people Michael refered you to; ( I
think it was the same ) anyway
 I helped bring Thomann - Hanry into the country as Director of Restoration
for the Cathedral St. John I was looking to carefully clean stone mullions
next to fragil stained glass and the gommage system did just that..its perfect
for friable surfaces as ..it is the only system i know that you can controll
the level of cleaning by adjusting the psi( see architectual record this
month)( also building stone mag that has Philly city hall on it) call Chris
Dissaux( dee-so)   212 736-1702
 tell him you know me (and get hung up on ) no...he will get you a
test..Regards Michael