This is a simple little oil lamp specially designed to burn fuels that are solid at room temperatures - such as leftover fats from cooking bacon, sausages, duck or other greasy foods.
It's made from pewter, using the lost wax casting method.
How The Lard Lamp Was Made
As in the previous pages, I made the form out of the malleable wax from the outside of Edam cheese.
I rolled a small ball of wax, then pierced it with a pencil and rolled it into a hollow cylinder. Then I trimmed off the ends and made four equally spaced lengthwise cuts at each end.
I slid out the pencil, then splayed out the cut segments at each end - shaping them into petals at the top, and simple feet at the bottom.
This wax is quite pliable at normal temperatures and with thin pieces like this, can be too soft to handle. A quick spell in the fridge firms it up, if necessary.
I added a few more details, then curved the petals back inwards - this is the crucial design feature, as these will be warmed by the flame, capturing heat to keep the fuel reservoir in a liquid state.
Once the form was complete, I hardened it in the fridge again, then added some extra pieces on the bottom to serve as pouring channels for the molten metal.
I've used clay for the mould in previous experiments, but decided this time to try Plaster of Paris. That was the plan, anyway, but I couldn't get hold of any, so I decided to try with decorating filler instead.
I melted the ends of the wax plugs that will form the pouring channels, then stuck them to the bottom of a cut-off plastic bottle.
I had to use more water than the directions on the filler pack recommended - in order to make it up to a pourable consistency.
It took all of the 450g pack of filler to completely entomb the wax form. To try to prevent imperfections from air bubbles, I agitated the wet filler by plunging a bamboo skewer up and down in each corner of the container (being careful to stay away from the delicate wax form now hidden in the middle.
The plaster took a long while to dry (probably because of all the extra water I added. After two days, it was solid enough that I could cut away the plastic container, which helped it to dry further by exposing all of the sides to the air.
I set it in a bowl on top of one of my central heating radiators for a couple of days, then, about a week after starting, I set about melting out the wax form.
As before, I did this by placing the mould upside down in the oven, starting at 150C and raising the temperature gradually over the space of an hour, finishing at 220C. Hardly any of the wax dripped out - only a few drips from the ends of the pouring channels.
Peering inside, however, I could see the mould void - as it later turned out, most of the wax had either evaporated away, or soaked into the porous matrix of the mould. Not what I expected.
Casting
I used pewter recycled from a dented old tankard I got from a charity shop again for this casting - take a look at the previous couple of pages for more details on how I prepared the metal for casting.
I melted the pewter and poured it into one of the filler holes - I was pleased to see it rise out of the other three and overflow a little.
There was some bubbling and hissing as steam emerged from the pouring hole, but this quickly died down - and crucially, before the metal had solidified. I tapped the mould sharply a few times to allow any trapped air to come out, but none noticeably emerged.
I left it to cool for an hour, then carefully broke away pieces of the plaster to reveal...
...A near perfect result. Some of the fine detail didn't come through properly, but the metal made it all the way to the tips of the petals, and there were no big holes - except the one I wanted, running through the middle of the piece, to take the wick.
I threaded a piece of cotton rag through the middle of the lamp, then placed it in a glazed bowl.
I melted some lard (leftover from frying sausages) and poured it into the bowl, up to the base of the petals, then placed the whole thing in the fridge for the fat to cool and set solid (so the first test would be a fair one)
Then I took it out and lit the wick.
It works perfectly - exactly as I had imagined - the recurved petals capture some of the heat from the flame, which is then conducted down through the metal and out into the four splayed feet at the bottom.
This melts the fat and enables it to continue being drawn up the wick to feed the flame,
Also, for the readers, perhaps you could try one of these thick wire egg cups?
http://ecx.images-amazon.com/images/I/51TQWH3VFTL._SL500_.jpg
with some additions, I think they would transfer enough heat.
(also, love the site- making a heart-shaped tin can box for valentines)
misobrilliant@gmail.com
http://www.atomicshrimp.com/st/content/lost_wax_casting/ Really cool process- thanks for sharing!
Alt: Could you put some mint extract in it to make it smell like minty bacon? Second: could you add some detail about melting the pewter (i.e., what kind of crucible and flame, and where to acquire the pewter)? Thanks. This is intriguing and I want to try it with my son.