Description
Fine-grained vulcanite that reads dark grey dry and turns deep black the moment water hits it. Pick the AC3040 when the heater is part of the room rather than something hidden behind a bench — the colour shift is the whole point.
Split-face stones store a lot of heat and stack with gaps between them, so air moves through the pile and a ladle of water flashes off a broad surface instead of pooling on top. Works in electric heaters, and as the visible surface layer on a wood-burning stove.
Natural stone, so no two pieces are the same shape. If your heater takes several boxes, order one spare: it lets you sort for fit and keep the pile loose, which is what actually protects the elements.
