High Heat Mortar Discovery Tools, Tips and Techniques Discuss High Heat Mortar Discovery in the Pizza Oven Design and Installation forums; Over the course of building my WFO I have found the sand grain size makes a big difference in workability ...

[DimTex]

Over the course of building my WFO I have found the sand grain size makes a big difference in workability of the mortar. Using the recipe in the oven plans I started with regular sand and found it hard to get good tight joints. I started sifting the sand and have found I can produce a much smoother mortar, less grainy with a longer working time and able to seal thin joints and best of all....it is stickier so I have been able to lay higher chains without a form or tool.

[MK1]

I am entirely to your way of thinking. I noticed the heatstop 50 has very fine sand and the homebrew I made did not seat as well like you say. Nice observation.
Mark

[Likeithot]

Using lime mortar is also a better mix for using in a WFO. I havent used clay so I can't comment, but definately using standard portland cement is a no no. It dries quickly and is not a recommended material for use in high temperature conditions. When I went to bricklaying school in Australia, we were told to only use lime mortar for areas in fireplaces and chimneys. That would also apply to WFO's.

[Tenne]

I used Silica sand #4 (type used for sand blasting). It is clean, fine and uniform in size and it makes fantastic high heat mortarwhen combined with cement and fireclay. A 50# bag in Saskatoon, SK., Canada is $6.00 and I used 4 bags for my 42" oven

[Lars]

I agree with Tenne!

The fine white sand at the lumber yard here ( nebraska) is about 4.50/bag and make the best mortar.