After my last dismal door attempt, I decided to make a new one. This one's a bit more complicated though. On hand, I had some aluminium scraps, some aluminium mesh, and a lot of vermiculite. And a nice wooden handle made from an oak branch, salvaged from my last two doors that didn't work.
I also bought a couple of meters of knitted stainless steel mesh tube from ebay: example link here. I cut two sheets of scrap aluminium (old land rover) to fit exactly in the door opening of my oven, and used the stainless and aluminium mesh to cover the sides. The whole lot was held together with a single thin stainless cable, passing through holes in the aluminium and through the mesh - stitching the panels together. I'd filled the mesh tubes with vermiculite before I'd assembled them into the door, and when it was all assembled I filled the door with loose vermiculite, packed it fairly tight, then screwed a plate over the hole I'd used to fill it. Finally, I bolted the oak handle back on.
As a picture tells a thousand words, these pictures are probably an easier way of describing it...
As luck would have it my oven entry is angled inwards, so this door forms a tight plug. I tested it yesterday and was pleased with it - from the graphs below it looks like it's at least as good as my previous Thermalite door and maybe even a bit better at holding the heat in.
It's about 4" thick, but is nice and light due to all the vermiculite. What would I do differently next time? Not use the knitted tubing - it looks good, but the plain vanilla aluminium mesh would have been fine.