Another mortar question

[Loafin]

Last fall I started building my oven with Tenax Mortar. The weather got cold so I quit for the winter. I just uncovered my project because its 55 degrees and I figured I could get going on it again. I had laid three courses of the dome. But when I started they all just fell off. Does anyone know about Tenax mortar, or should I be using something else instead???
Thanks for any help.

[Tscarborough]

All I could find is the MSDS sheet, but it looks to be an airset water soluble mortar, fine for indoor fireplaces, not so good for outdoor work.

[dswiggum]

Tenax is a air set water based high temperature mortar. It is rehydratable. Because it is an air set it takes quite a while for initial firm set. That's OK if you are laying plumb and level, but if you are laying a tilted course you will have to be patient, laying one course and waiting for it to firm up a bit before continuing. With a masonry fireplace, the tilted courses form the smoke shelf and can be backed (filled) with a fireclay mortar/firebrick rubble mixture up to 8" from the top of the back wall of the firebox. From that point upward you can plaster the back side with the fireclay mortar mix up to 1" thick. I use 1 part fireclay, 1 part portland, 6 parts fine sand. When you are doing an oven you will likely need to support from the interior for at least a couple of hours (more if the weather is cool and humid) and take it slow. I have found the Tenax to be an excellent product for interior (weather protected) use.

[Loafin]

Thanks swiggum
I found some fire clay at a local pottery place so I think I'll go with that instead of the Tennax.Thanks for the info!