Furnace Part II

Construction of the new furnace! With a fair bit of help from Lionel Oliver's book - "The flowerpot crucible furnace", I went about scrounging for materials to use.

In the end, an old paint tin was finally put to good use after having its insides hosed with high pressure water, and then sliced through with an angle grinder. The flowerpot shown fits perfectly in the sawn off tin.

Raw materials to be used for the furnace

A messy tabletop full of random tools

Two holes are bored in the "revitalised" paint tin - the first is for the blower attachment (in order to pump oxygen through the coals), and the second through the lid to allow ventilation.

I had originally planned to use the old paint tin handle as the furnace lid handle. However, there was the inherent risk of the handle being off balance after the lid was filled with concrete. Thus, the old handle welds were cut off, and a new handle riveted in place above the concrete line.

Cutting off the old handle with a cut off disk

Reinforcing the lid

The lid is fitted with interwoven thick core steel wire to help strengthen the cement as it hardens.

Here is the lid with cement poured in. The cement is jabbed at rather vigorously to ensure no air bubbles are left in the mix. The vent hole is formed using a piece of PVC pipe.

The cement in the lid and body of the furnace will be left for four days (that was the longest I could wait...) to cure and harden.

Prodding the lid cement and abusing the air bubbles

Cutting off a segment of steel tube for the blower pipe

While the concrete sets, the blower device is constructed. For this, I utilised an old fume extractor originally designed for sucking up soldering fumes.

Here, a piece of steel pipe is being cut to attach the blower to the furnace.

The cement has finally set (maybe), and here is the blower attached to the furnace via a very "ergonomically" designed air tube made from random foam cups, pvc pipe and steel tubing.

The furnace complete with blower attached

A look inside the furnace with air distributor

Here is a view of the body of the furnace. I have to admit I totally ripped off the idea of the air distributor device (angle iron) from Lionel Oliver's design, but seeing as I had a right angle shelving bracket leaning right on the shed, I just couldn't resist.

The air distributor works well. In the old "dodgy" furnace, I didn't have this element and as a result only the charcoal right next to the tuyere hole was heated adequately.

A small fire was lit in the furnace to test out the blower and also to finalise the setting of the concrete. Actually I ended up having so much fun that the "small" fire turned into one which would consume a whole pile of backyard junk. So much for reducing greenhouse gasses.

The furnace happily crackling up with a small fire

Juicy hot flames rocketing out of the vent hole

The blower works amazingly well... Intense heat is generated in the furnace whenever the blower is turned on, whereas the flames are reduced to mere billowing smoke when it is off.

I left the PVC pipe former in place to burn off, which was certainly easier than hammering it out and risking the integrity of the furnace lid.

Furnace (part II)