Well, here it is! But not without some unforeseen "opportunities" rearing their heads. First it had rained Monday so the garden centers pots were wet. Not a deal breaker. The largest chain garden center here had surprisingly horrible clay pot selections as all the styles I was looking for were plastic or resin. I ended up at Home Depot which is a huge hardware/garden chain in the US. I chose pretty plain pots and put them in the garage under fans over night. Yesterday I marked my cuts and got to work. I sure wish I'd have just got that diamond blade for the angle grinder first! No matter what I've read, a hand saw, hack saw, reciprocating saw with differing blades, and metal grinding wheel on the angle grinder are frustrating time and energy wasters. I ran to the local hardware and picked up a 4" diamond blade for $16 and cut the top pot in about a minute. The vermiculite was a rather fine grind, but a 2 cubic foot bag was more than enough. I used a clay pot saucer for the bottom ring as we discussed. I just used the angle grinder to cut the center out. Minus the blade and new welding gloves, I got it all for under $100. Additionally, my wife found a cure solution recipe online that's apparently used in tandoors. A simple mix of salt, sugar, spinach and vegetable oil went in the blender to make a slurry/paste. I smeared it on the inside of the oven pots and let it dry. Smeared the rest once again and left it over night. I put it together and fired it up slowly this morning. It seems to be working perfectly! We've had chicken marinating in a madras curry and yogurt mix over night to test it out this evening. If this works out, I may cook on this every night for a month!
You know that sound you hear a minute or so after pushing down on the cans and plastic bottles in the recycle bin?
So everything was going great. Piping hot oven, skewers cooking nicely, side dishes prepped. I was in the kitchen, and my wife was on the back porch with the kitchen door open. I hear this sound and totally think it's the trash settling. She comes in and asked why she heard a loud ping sound coming from the yard. I swore it was the trash and moved on.
We finished the meal (which was great) and I went outside to make sure everything was cooling off ok. Then I felt the large outer pot and there it was. A crack from bottom to the middle.
Talk about the wind being taken out of your sails!
The pot was fully dry, so the only thing I can imagine is that I let it get too hot. Or I bought a bum pot, since I inspected it well for cracks before I bought it. I also never saw a temp on the outside pot higher than 120f and was checking it often. As mentioned, I raised the oven pots off of the bottom of the outer pot with a pot tray ring before the vermiculite went in. I added additional holes to the bottom oven pot, and raised the coals inside using a perforated pie tin, so there was a full 2 1/2" between the outer pot bottom and the actual coals. I only left the single factory hole in the bottom of the large pot. The outer pot thickness at the bottom is roughly 1/2". To add insult to injury, it was the $50 pot! I also used lump charcoal instead of briquettes, which some say burns hotter, but I didn't think I used too much. I also checked the inside temp often, seeing high 800's only occasionally.
Based on what I've described and the attached photo, I welcome any ideas you have as to what may have happened. All the pots are very standard red terra cotta Deroma brand with Italy stamped in the clay.
I did wonder about posting this blog, as some people might get scared off from building one of these Tandoor, but I believe in honesty and sharing the highs as well as the lows. What I can say, I have seen this problem with either of my ovens. The second oven is nearly two months old and I have used it every week since making and often twice at the weekend. I have also regularly done burns for 8 hours, where I have cooked at lunch and then again for evening dinner. The outer pot is in perfect condition and the inner pot has a couple of very fine cracks which don't affect the performance. I have also being contacted by lots of people that have built an oven without problems.