Question:  But the new cast-iron of the 1860's can be made to look just like the stone of other mid-1850's commercial buildings.  Why can't I use cast-iron and retain the architectural integrity that makes it special?

Answer:  Because real stone facades of the 1850's, just as any other historic building material, possesses a richness of quality and texture developed over the years that is impossible to manufacture in modern mass produced material, like James Bogardus' cast-iron.  This is especially true of  stone with special details such as tooling or chasing.   Modern, mass produced cast-iron imparts a hard, opaque surface to a building that is especially evident when surrounded by the mellow richness of historic building materials.   Also, bolts may rust away, and the cast iron may trap moisture inside, causing rot.  If, say, the Soho area had been built of cast-iron buildings, they would certainly have fallen down by now.

Cast iron isn't a micron (or 22 gauge) thick like aluminum siding. It also is substantially more rust-resistant than steel, which is part of the reason you see more 1850 buildings than 1950 cars.  I would also pernt out that guys like Robinson Iron frequently make replacement parts for CI buldings, fountains, etc. out of cast aluminum, and nobody bitches about it.

 

I suspect part of the problem with aluminum is its thinness, or more precisely lack of thickness, which enables you to do a Christo job on your house.  If one could get aluminum clapboards and window surrounds made to repalce deteriorated wooden elements, rather than cladding them with tissue-thin formed aluminum sheet, would we bitch?  Then there's this godawful glossy white plastic crap that everybody's making deck railings and trellises out of... 

 

Ralph