Just in response to Adrian's comment I have one of these furnaces purchased ex China. Looks good but I have not used it in anger yet. However, I am impressed with the Myfordboy video which gives me some additional confidence.
These kilns, which all look the same in all the pictures, actually come in a range of sizes based on the weight of material that can be melted in the graphite crucible provided. However the weight of material is quoted for gold – so you can't melt as much aluminium for your money – a higher weight can be achieved with brass or zinc – same volume its just the metal which has a higher specific gravity. It took a few readings of the description before I twigged to this and fortunately ordered the largest size. It's still not huge but should be adequate for smaller parts.
Pero