Producing garum was relatively simple. A garum maker such as Aulus Umbricius Scaurus would have first placed a layer of fish entrails on a bed of dried, aromatic herbs such as coriander, fennel, celery, mint and oregano.

Then he would have covered the fish entrails under a layer of salt about two fingers high. The layer sequence — herbs, fish and salt — was repeated until the container was filled. The concoction was then left in the sun to macerate for a week or so, and the sauce was mixed daily for about 20 days.

The process produced a smelly liquid — a local delicacy to the Romans.

(It sounds nasty but they still prepare a variation on garum down there -- I ate some and it's really really tasty. I don't advise leaving it for 2,000 years out of the fridge)

Enh, Vietnamese or Thai fish sauce is still made in pretty much the same way. And DAYUM I love me some of that.

Yeah, sounds just like fish sauce... only much quicker.

That is totally fascinating. All of it. Partly, I'm interested in the disgusting sound of rotting fish entrails as a kind of Pompeiian ketchup. ewwwww. But maybe garum better than it sounds. It must be.

Such an interesting and logical sounding calculation of the volcanic eruption date.