Bob,

John “Doubleboost” Mills posted a couple of video reviews on the 6Kg and 12Kg Vevor furnaces about a year ago.  His reviews are no flannel, down-to-earth ones.  If they’re no good, he says so – in his own inimitable way!

Here’s a link to the 6Kg one.

And another to the 12Kg one.

He uses gas – propane, I think, to fire these up.  They seem to work OK.

John (not Mills)

You could try on here
https://www.academia.edu/115318929/Building_A_Gas_Fired_Crucible_Furnace

free download David Gingery crucible furnace.

I made one of these a long time ago 1990 i think
but used heat resistant bricks for the lining ,gas fired with propane  electric blower  .

This is the only photo i could find holds maximum A8 crucible
about 20 lbs cast iron /brass ,you need a fair bit of
other stuff to go with it moulding flasks , sand , tooling
protective clothing .

https://www.artisanfoundry.co.uk for foundry supplies.

You can use play pit sand for the molds and sodium silicate
binder they sell it or you can make your own with gel
cat litter and drain cleaner (sodium hydroxide).

John

I reckon it often doesn’t save much money (if any) to make your own. I think I’d go vevor or similar for a new big furnace or forge. Gas for larger castings.

Burners are simple to build, particulary forced air, but there is an art to getting an efficient natural air fed burner. For smelting, maybe a fine tuned burner isn’t so important as it is for forging, but consider Amal https://amalcarb.co.uk/amal-gas-injectors/propane-injectors.html which are the best of the best – really good control.

The 1-3KG electric furnaces are very convienient. They only just get to temp for pure copper… maybe not always… but it is rare to smelt pure copper and any alloy will melt at a lower temp. Ideal for making small billets of non-ferrous alloys or small castings. And you can use them indoors with care but you probably don’t want to pour significant castings (bigger than jewellery) indoors. You can use metal crucible in them as the heating element will touch and trip the RCDs in the house.  i use one as a salt pot for high and low temp salts for heat treating small items.

Lets get the technical term correct. We are melting metal not smelting.

“Smelting is a process that uses heat and chemical reactions to extract a pure metal from raw ore (rock containing metal)”