There's an inconvenient truth that preservationists typically gloss over in their ever-more-pressing fight to save Chicago's mid-20th Century modernist buildings from demolition:

Many of these steel buildings are tough to love.

Perhaps it's their cool abstraction, or their labyrinthine floor plans, or their harsh materials, like the serrated concrete that can practically cut your skin.

Whatever the reason, the American public has yet to cotton to these metal buildings.

A survey of America's 150 favorite works of architecture, released in February, didn't contain a single creation by Ludwig Mies van der Rohe, Chicago's master of steel building.

But popularity is one thing. Quality is another.

A half century ago, when Space Age America was infatuated with all things new, there wasn't yet popular support for preserving old metal buildings.

They were too old to be new and too new to be old. And so, they were torn down, shortsightedly. Now the question is whether we're about to make the same mistake again.

Danger abounds.

In Cleveland, public officials want to destroy Marcel Breuer's brooding, 29-story Cleveland Trust Tower, its facade a honeycomb of rough concrete, and replace it with a midsize office building.

In Boston, officials are pushing a plan to sell City Hall, a monumental hunk of concrete, and build a new government center on the waterfront.

Even in Chicago, as several iconic modernist metal building structures (Crown Hall, the Daley Center and the Inland Steel Building) have been restored or put on protected landmark lists, many little-noticed modernist gems have not.

A dozen years ago, the City of Chicago completed a sprawling survey of potential landmark buildings across the city and came up with an official database of 17,371 significant structures.

But, with a handful of exceptions, the survey stops in 1939.

So post-war commercial metal building structures remain uncovered by the Windy City's demolition delay ordinance, which requires officials to put a hold of up to 90 days on the issuance of a demolition permit for buildings rated in the top two tiers (red and orange) of the color-coded survey.

In other words, these metal building treasures get no hearing on whether they deserve a stay of execution.