Tandoori Problem

[tttman]

I am making a tandoori oven using two 18" ceramic flower pots that are attached top to top with chicken wire. I found a recipe online for refractory cement and I don't think this will work. 1.5 parts portland cement, 2 parts sand, 2 parts perlite and 2 parts clay. I slathered this all over my pots and it is now cracking. The stuff that fell next to pots is grey and very crumbly.

What should I use to cover the outside of my pots?

When I fill my outer container with insulation, is perlite and lava rack sufficient?

thaks

[SableSprings]

Re: Tandoori Problem

Forno Bravo sells a fabulous refractory mortar mix...well worth the money for most folks. Making your own "home brew" refractory mortar is discussed at length in the thread I've noted below.

http://www.fornobravo.com/forum/f6/high-heat-mortar-primer-914.html?highlight=home+brew+refractory+mortar

I've never seen perlite in anything other than an insulating component (never in a refractory mortar). Lots of good info in the above thread. Plenty of documentation in the forum on insulating with perlite or vermiculite. Insulation tends to be either a ceramic fiber blanket or perlite/vermiculite with just portland cement (usually recommended ratios anywhere from 6:1 to 10:1 as non-structural material). Portland cement does not stand up to the high temperatures of a WFO or Tandori, so in those cases the additional components in refractory mortar are really important...lime and/or calcium aluminate being the major structural materials that stand up to high heat.