Heat resistant mortar
Normal mortar will expand and crack very quickly when exposed to the temperatures of a woodfiring pizza oven. So we need to make a heat resistant mortar mix. even then we don’t want mortar between the bricks facing the heat. On the next page I will discuss how we did the dome with no mortar showing!
The formula we used was…
10 : 6 : 3 : 2 – Sand, Fire Clay, Lime and Portland cement.
Sand, lime and portland cement are readily available from builders yards – the fireclay I got off ebay from a pottery/kiln supplier. The fireclay was about £10 a 25kg bag plus a big P&P! Apparently the cement will eventually burn out – the lime and clay do the sticking and the cement is just to initally get it to set. There you go!
I’d never used a cement mixer before, so learned the technique fast as my bricklaying friend did the build. The formula is used for shovelfuls of the material. each mix will fill a standard cement mixer. We discovered that it’s easiest and quickest to mix if you add the sand, cement and lime with a good squirt of fairy liquid (poor man’s plasticiser) and water and then add the fire clay – otherwise it is lumpy and takes ages to mix.
Lime is nasty stuff and will damage your eyes and lungs badly, so take care and wear goggles and gloves for protection…