Ceramic insulation over cob/clay oven - how?

[zzz]

Hi folks. I've built several cob / earthen ovens. Most recently, I've used a clay+straw insulation around the dome that has actually performed very well, but because it's such a thick layer, it adds a lot of diameter to the overall size of the oven. Not to mention, a huge foundation.

I'd like to consider using ceramic insulation blankets over my next oven. However, I have a couple of concerns. Primarily, I'm unsure how to secure the blanket to the cob dome, and what kind of lath to use over the blanket... and how to secure that as well. Normally, I do a clay-based plaster over my earthen ovens, but clay and metal do not go well together. It's possible, but I would prefer to avoid it. But I'm unsure how to affix it other than using some kind of nail, which is not the greatest either...

Any thoughts out there? Anyone attempt using ceramic blanket insulation over a cob dome? Thanks for the help!

[david s]

I don't use any kind of lath over the blanket. I just sit it there and then add a layer of 10:1 vermicrete over the top around an inch and a half thick. Eyeballing the profile and tapping the surface with the flat of a trowel achieves a very accurate spherical surface. This is sufficient to even out the lumps and bumps in the blanket. Once dry and then all the moisture purged from the oven and insulation layers the final render outer coating can be applied. Adding and securing mesh over a spherical form is time consuming and pretty pointless IMHO if you have a vermicrete layer holding it all in place anyhow.

[zzz]

Simple enough, I like it. Thanks for your input David.