Materials guide

Solids

• Wall — Wall is the permanent frame of a scene: nothing in the simulation moves it, burns it or dissolves it.Wall is static and appears in no reaction table, acid included, so flames, lava and acid all leave it exactly as painted. Its listed weight of 9 ties with metal for the top of the scale, but static cells never take part in sinking, so that number has no visible effect. The edges of the canvas behave like an invisible strip of wall as well.Tip: Draw containers from wall when they have to outlast everything else in the scene, and switch to stone or metal only when you want acid to be able to open them later.
• Stone — Stone is a fixed block of grey rock that ignores heat entirely and gives way only to acid.
• Metal — Metal is a pale, heat-proof block that acid cuts through faster than it cuts stone.
• Wood — Wood is a solid, flammable building block: fire and lava turn it into flame, and acid eats it quickly.
• Plant — Plant is static green growth that slowly turns touching water into more plant and burns faster than wood.
• Ice — Ice is a faintly glowing static solid that freezes neighbouring water and melts on contact with fire or lava.

Powders

• Sand — Sand is the reference powder: it falls, piles into cones and settles under every liquid lighter than itself.
• Salt — Salt is a white powder that behaves like sand until water touches it, and then slowly disappears.
• Ash — Ash is a grey, inert powder for texture: no reaction creates it and none consumes it.Ash falls and heaps like sand but is lighter, at weight 4, so sand, salt and gunpowder poured onto it push down through the layer and leave the ash on top. It is still heavier than water and oil and settles beneath them. Burning does not leave ash behind in Sandlab, so every grey grain in a scene was put there by hand.Tip: A thin dusting of ash over a burned-out area suggests what a real fire would leave behind, and it will never reignite or react with whatever you paint next to it.
• Gunpowder — Gunpowder is a dark powder that flashes into fire at the touch of flame or lava, carrying a burn along any trail it forms.
• Seed — Seed is a light green powder that sprouts into plant wherever water reaches it.

Liquids

• Water — Water is the central liquid of Sandlab: it levels out, puts out fire, cools lava and feeds most of the slow reactions.
• Oil — Oil is the lightest liquid in Sandlab: it floats on water and acid and catches fire readily.
• Acid — Acid is a glowing green liquid that eats wood, metal and stone without being used up, and destroys itself only against water.
• Lava — Lava is a heavy, brightly glowing liquid that sets wood, plant and oil alight without cooling down, and turns to stone when water or ice reaches it.

Gases

• Fire — Fire is a short-lived, brightly glowing gas that rises, spreads into fuel and then burns out on its own.
• Steam — Steam is a pale, faintly glowing gas released when water meets fire or lava, when acid meets water, or when fire melts ice.Steam has weight 1. It rises through empty space, anything heavier passes down through it, and it reacts with nothing. Each cell expires on its own after 160 ticks and leaves empty space; the simulation advances one tick per screen refresh, so how long that feels depends on your display.Unlike real vapour, it never condenses back into droplets. Water that has turned into steam is gone from the scene for good, so a large cloud is a record of how much liquid a fight with fire or lava has cost.Tip: Watch where steam is rising to find out where your water is being spent.
• Smoke — Smoke is a dark, inert gas that rises and clears by itself, and it exists only where you paint it.Smoke shares steam’s weight of 1: it drifts upward through open space and heavier materials fall through it. No reaction produces it, burning included, and nothing reacts with it, so it can neither spread nor smother a flame. Each cell lasts 120 ticks before vanishing, so a painted plume thins out from its oldest parts first rather than drifting forever.Tip: Brush a little smoke above a chimney or a burning building for atmosphere; it clears itself and leaves no clutter in the finished picture.

Every reaction

Reactions happen when two cells touch. The odds are per contact check: each tick, cells that touch inside the same two-by-two block of the grid are checked against the table, so even a small chance tends to happen soon after contact. This table is generated from the same data the simulation runs on.