Salt and fermentation, acids and alkalis, then synthetic nitrogen and polymers.
Secure a mineral you cannot live without and cannot grow.
Needs first: Fire, and keeping it (Energy), Containers
Put microbes to work — your first biotechnology.
Needs first: Pottery and the first kiln, Plant staples (Food), Blacksmithing (Tools)
Make sulphuric acid, and with it most of industrial chemistry.
Needs first: Glass, Fermentation and distilling, Lime
Make soda ash and caustic soda at scale.
Pull fertiliser out of the air.
Needs first: Electrochemistry and light metals, Blast furnace and cheap iron, Acids, Petroleum and refining (Energy)
Make materials with properties no natural material has.
Needs first: Petroleum and refining (Energy), Acids, The factory and interchangeable parts (Tools)
Every guide, build, reference sheet and book reached from the steps above.
What matter is made of and how it changes: amounts, gases, acids, the energy and speed of reactions, electrochemistry, and the reactions every industry on the ladder runs on.
Level 1A glut eaten in the week it arrives is a feast. The same glut dried, salted, fermented or cellared is the difference between March and a famine.
Level 3The two dozen that decide who lives where there is no doctor: what each does, how it spreads, what kills it and which step stops it.
Level 3The basic set from the WHO list: what each treats, what it is made from, and the earliest tier that can make it. No doses, on purpose.
Level 1The poisonings a rebuilding community is most likely to meet: where each comes from, how it shows, and the first thing to do.
Level 3Fourteen branches, each with the handful of results a civilization cannot rebuild without, and where to learn the rest.
Level 2How to tell the ores that matter with nothing but a streak plate, a knife and your hand: colour lies, streak and weight do not.
Level 2Burn a rock, add water, and it turns back into rock in the shape you gave it. Mortar, plaster, whitewash, soap and tanning all start there — and so does an alkali burn that can blind in seconds.
