The red altar's masterstroke

Look toward the high altar, and the red almost hums — deep, polished, expensive-looking, the kind of stone a prince would have shipped across the Alps at ruinous cost. It was never quarried. It's stucco marble: a mix of gypsum, glue-water and colour pigment, worked and polished by hand until it takes on the depth and sheen of the real thing.

In the 17th century this was no shortcut. Stucco marble was a demanding, highly prized craft. It was lighter than solid stone, it could be poured and shaped far more freely, and — the part the Baroque loved most — it could be given colours and veining that no natural quarry could reliably supply. A red exactly this warm, this even, running the full height of an altar: that was the artisan's triumph, not the mountain's.

The man behind it was Christoph Bruck, who built the towering high altar to designs by the Jesuit Heinrich Mayer, and who also made the pulpit in 1673. Run your eye from one to the other and you're looking at the same hand, the same illusion, pulled off twice.

And once you know the trick, the whole church starts to give itself away. Much of what reads as carved architecture here — the pilasters, the mouldings, the framing — is modelled in stucco rather than cut from stone. In this building the plasterer, not the stonemason, is the leading man. The Baroque wasn't only interested in showing you something precious. It wanted to show you what a skilled hand could make precious.

So when you stand before that red altar, you're not looking at a cheaper substitute for marble. You're looking at a performance — one that fooled far sharper eyes than ours, and still does.

Curious how plaster becomes marble? Scroll down to the chat and ask me — I'm right here.