Building the Foundry

Tue, 02 Jun 2026 00:00:00 +0000

Started with tin — a small camping burner and a steel ladle was enough. Then the obvious question came up: could we melt the aluminium cans now?

Aluminium needs higher temperatures than tin, and the gap matters:

Metal	Melting point
Tin	232°C
Zinc	420°C
Aluminium	660°C
Brass	~900°C
Copper	1085°C
Cast iron	~1200°C
Steel	~1370°C

We looked at buying a small foundry online, decided it would be more fun to build one. My son and I built it.

The Build

Sand and gypsum cast inside a metal rubbish bin, steel mesh for reinforcement. Used an old fire extinguisher as the form for the central cavity. Added a pipe for the air inlet and a hair dryer to force air through — charcoal from the grill as fuel.

The foundry.

The hair dryer died on the first serious session. First upgrade: a proper fan from Biltema.

What We’ve Melted

Once the foundry was running we tried everything we could get hold of. Also picked up some wax for eventual lost-wax casting experiments.

Material	Source
Tin	Second-hand shop finds
Aluminium	Cans + scrap
Brass	Scrap
Copper	Scrap
Wax	Candles

Photos to follow.

We bought some tooling online — tongs, crucible, mould for casting bars.

Tongs, crucible, and bar moulds.

And ofc safety kit on every session: heat-resistant gloves, safety glasses, face mask (steam explosions from moisture in moulds are real), fire extinguisher within reach, and distance from anything hot.

Stock — Bars Cast

Melted-down material poured into bar moulds for later use.

Material	Stock
Tin	1047g
Aluminium	1398g
Brass	200g
Copper	2310g
Wax	1730g

Cast bars ready for future use.

Moulding Methods

Different methods suit different metals, temperatures, and detail levels.

Silicon mould — works well for tin and other low-temperature metals. Quick to demould, picks up good detail. Proven success with the scout badges. Not suitable for aluminium temperatures.

Gypsum mould — tried with tin, not great. Must be completely bone-dry before the pour or moisture turns to steam instantly.

Green sand — mixture of sand and a binder that holds a mould impression. Tried making it from cat litter as the binder. Goes into a flask — we made one from wood. More experiments needed.

Red sand / oil sand — similar principle to green sand but oil-bound. Don’t have any yet.

Lost-wax casting — make a wax model, invest it in plaster, burn out the wax, pour metal into the void. Haven’t tried it yet. I have melted some candle stumps for the wax stock, will try and go from there.

Next: Casting Part 1 — Scout Badges

Casting Part 1 — Scout Badges

Tue, 02 Jun 2026 00:00:00 +0000

When I was a kid and scout we cast the scout emblem in tin — naturally we had to do this again with my own troop.

I’m lucky to have a fellow scout leader who does casting professionally. I modelled the master in resin and he made the silicon moulds from it.

For the tin, I went to second-hand shops and gathered everything tin I could find to melt down. Ordered crucibles and pliers online. We melted the tin by putting the crucible in the fire, then the kids could do the pour into the mould, demould, and finish.

First real casting project — a success.

Master

Modeled in Blender, printed in resin as the master for the silicon mould.

↓scout_emblem.blend ↓scout_emblem.stl

Moulds

Silicon moulds made by my fellow scout leader from the resin master.

Silicon moulds made from the resin master.

The Pour

We set up a practice station first — gloves, face masks, and pouring water into a PET bottle before anyone touched real tin. Once they had the motion down, they moved to the actual pour.

Done in small groups: two leaders, two kids at a time. Went smoothly.

Result

Finished tin scout badges.

Metalwork on Backend Engineering Strategy Tools