High Heat Mortar Primer

[david s]

Not absolutely sure,but I think the masonary cement is 50% portland and 50% lime anyway. You might need to contact the manufacturer for specs. or just do the mix yourself.

[tdibratt]

Went to a local masons yard and turns out I was able to buy Portland Lime. It is a mix of portland cement and lime 1:1.

Perfect.

[Dutchoven]

Not really sure how I missed this posting and apologize for it...type N masonry cement is mixed at 50/50 portland to lime as is portland lime mix...in this instance it should be 2 parts cement 1 fireclay and 3 sand...that is exactly what I used for our oven build and it dried nice and hard quite quickly...although we haven't fired it yet I am confident in it as a mix...that will also work well for rendering the dome if that is how you plan to finish it as the type N is a bit stickier than other types of mortar...for the render you can add more sand...typically type N gets anywhere from 6 to 9 parts sand when being used to lay brick
Best
Dutch