Regular mortar or refractory mortar

[biondoli]

I am going to finish my second oven (insulated) with porcelain tiles, should I use refractory mortar or regular tile mortar?
With the first oven I used regular mortar and beside little cracks it is still holding (6 years old), just wondering if refractory mortar would be better but I don't know if it work well with porcelain. Thanks for any suggestion!! Thanksssssss

[Tscarborough]

Re: Regular mortar or refractory mortar

Direct contact with flame=refractory mortar.