Today we’re planting - well, laying - a large crop of engineering bricks to keep finishing off the paving around the tipi circle.
Engineering bricks are great for paving because they're very frost resistant. Frost damage to bricks is caused when they absorb water then freeze. The water expands as it freezes, which gradually breaks the bricks apart. Engineering bricks are fired at really high temperatures which makes them different from normal bricks- and often makes them blue too, as the iron oxide in the clay goes from being rust (hydrated iron oxide) which is red, to anhydrous (no water) iron oxide, which is bluey black. Around here, lots of old reclaimed blue engineering bricks are Staffordshire blue bricks from Etruria, just down the Trent and Mersey canal!