How to build your own tandoor from a flower pot

It is easy to buy a tandoor in the UK if you are prepared to pay for one of the restaurant ones. However, these are too expensive for someone who only wants to perform the ocasional bit of tandoori cookery so when I wanted a tandoor of my own an alternative solution had to be found. A possibility was to buy only the liner of a commercial tandoor and mount it in my own surround but this was considered to be too expensive. Instead I decided to use a 43cm(17") terracotta plant pot with its bottom cut off as my tandoor liner and mount it in a metal cylinder with vermiculite insulation. This page describes the construction of my tandoor in detail.
My first step was to locate a suitable outer cylinder. I settled on a scrap copper hot water cylinder because it was almost exactly the right width in which to mount my clay liner. I was able to cut the top off the cylinder with an electric nibbler, you could perform the same task but more slowly with a hand nibbler. I then had to remove all external pipes and water fittings, the pipes were simply sawn off with a hacksaw but the fittings had seized up rather well and needed some fairly hefty persuading to remove. I found that unexpectedly my cylinder contained a complicated piece of brasswork designed to circulate hot water from a central heating system, this simply came away when I finally managed to shift the heating element mount.
Once I had my empty cylinder with no top I put a shovel full of sand in the bottom. This allows the firebricks to go on top of the sand and bed into it without touching the base of the cylinder which is slightly domed. The aim was to have the top of the firebricks level with the opening proviously used by the heating element, in this way I could use the hole as an air hole, so I had to get the sand level right by checking it against one of the firebricks. I tried to tamp down the sand a bit using one of my firebricks. At this point I went round the smaller pipe holes in the cylinder and blocked them with big blobs of fireclay. These remain soft until the tandoor is first fired, but thereafter they harden up very well.
To fit my firebricks into the bottom of the cylinder on top of the sand I had to cut some of them to shape using a hammer and chisel. In my case I was using some recycled firebricks from a scrap kiln and they were relatively easy to shape in this way. Once I had fitted my firebricks into the cylinder I removed some of the surplus sand you can see in this picture and filled any cracks between the bricks with fireclay to stop any sand escaping.

My next step was to turn the flower pot into a home made tandoor liner by cutting the base away from it and cutting an opening in its rim to line up with the former heating element hole that I was using as an air hole. Both these cuts were made with a hand held angle grinder fitted with a stonecutting wheel. At this point I should point out that angle grinders are dangerous and should only be used with great care in the approved manner. No tandoori kebab is worth cutting yourself up for!
The bottom of the pot was cut off by running the angle grinder round the side of the pot about 20mm (0.8") from the bottom of the pot as shown in the picture. In places I did not go deep enough so even after cutting the base remained attached to the body of the pot. A gentle tap with a mallet separated the two pieces though. The side cut required a little more care than the top cut. In effect I made 3 cuts at right angles to each other to make a rectangular opening in the rim of the pot. To reduce the risk of cracks where the cuts met I first drilled a 10mm(0.4") hole with a masonry bit at each of the meeting points. I them made my three cuts with the angle grinder and the offcut of pottery just fell out. Both pieces of offcut pottery are worth saving, in my case the base of the pot makes a perfect tandoor lid and I ended up using the small side offcut behind the blob of fireclay I used to block one of the bigger holes in my cylinder.
Once I had created my liner from the pot , my next step was to lower it into the cylinder. As it happened, it was an extremely tight fit, and I was worried that I would break it. A significant part of the strength of a flower pot comes from its base and without the base it felt a good deal less solid when picked up. With care though I was able to lower it safely into the cylinder where it rested level on the fire bricks. I had to rotate it round a bit before the gap in the rim lined up with the air hole. Once the pot was safely in the cylinder my next task was to seal the crack between the pot and the firebricks with fireclay from the inside, and to seal the gaps between the cylinder and the pot around the air hole. This last task used quite a lot of fireclay but resulted in a good seal round this appeture which did not allow any of the insulation to escape. At this point the ergonomics of the finished tandoor began to be apparent. I couldnt quite smell the kebabs, but here was something starting to look like a tandoor.
Once the fireclay was in place and all the holes and cracks had been sealed I could then pour in the vermiculite insulation. I bought a big sack of vermiculite from my local garden centre, this was more than enough to fill the space between the cylinder and the pot up to the level of the top of the pot. As I used the tandoor the vermiculite settled a bit, it is possible this was due to moisture being driven off by the heat.
Finally, I cut a plywood ring to cover the vermiculite. The idea was that this would provide a good top surface for the tandoor but unfortunately the heat was such when the tandoor was fired that instead of the scorching I expected it burned away almost completely in places. It has since been replaced with a layer of bricklayers mortar, with a 1mm expansion gap between mortar and pot made by running the tip of a bricklayer's trowel round the edge of the pot while the mortar was wet. This mortar has proved to be a good solution to the tandoor's top surface, having set hard and not cracked despite getting very hot.
Having used this tandoor for a while now I am pleased with its performance. Aside from the problem with the plywood ring and one crack from top to bottom in the liner it has not shown any design flaws. The crack may even make it more reliable as it may allow it more ability for expansion. I have mostly cooked naan breads and kebabs in it, with the ocasional piece of chicken and a few tries at more conventional BBQ food tandoor style. It fires very easily with standard barbecue charcoal, and while a little experimentation was required to discover that laying the fire in a C shape facing the air hole gave best heat it has always given me enough heat to quickly cook anything I can throw at it.