Nothing went to waste
Roman garum wasn't made from the fish you'd want on a plate. It was made from what was left over: heads, viscera, blood — the parts of a mackerel, sardine or anchovy that go straight in the bin today. That wasn't scarcity or improvisation; it was precision. The viscera carry the enzymes that break down the fish's own protein, so they were, quite literally, what drove the whole fermentation.
Everything went into large clay vessels in layers: fish, salt, fish, salt. Salt had exactly one job — stop the mixture rotting before it had the chance to ferment properly.
The sun as the only oven
That's where the technology stopped. The climate did the rest: the vessels were left out under the Mediterranean sun, at what were known as cetariae — coastal works like the ones at Baelo Claudia or Cartagena, the same sites I mentioned in the first chapter — for weeks, sometimes months, stirred every so often. The heat sped up what the salt and the fish's own enzymes had already set in motion.
What got strained off at the end was an intense, amber-coloured liquid. Pliny the Elder is said to have likened its scent to Rome's finest perfumes — hard to picture if the only fermentation you've ever smelled is one still halfway there.
Salt, time and sun — no other technology was involved.
A method that never quite left
Rome fell. The method didn't — it adapted, along different coastlines. Colatura di alici, on the Amalfi coast, is still drawn drop by drop from anchovies cured in salt for months: a near-direct descendant of Roman garum. Southeast Asian nuoc mam runs on the same principle, even if nobody there thinks of it as Roman.
What I do in my own kitchen — I covered it in the previous chapter — isn't an exact replica of that process: I use whole fish, not viscera, and work under conditions Rome neither had nor wanted. But the underlying principle hasn't changed in two thousand years: salt, time, and letting fermentation do work no modern technique can replace.
