- Home
- Wiki: Smelting and fuel
Wiki
Smelting and fuel: hot enough to matter.
A Furnace turns ore into metal, sand into glass and clay into ceramic. Whether it works depends on three things: the temperature the job needs, the fuel you burn and the walls you built.
The three rules
- Every smelt has a temperature. For a metal it is 85 per cent of the metal's melting point (never below 200 degrees). For glass, ceramic and the like it is 75 per cent of the lower melting point.
- Fuel sets the flame. A fuel burns at
600 + 30 x its energydegrees. The fuel in the fuel slot must burn at least as hot as the job needs. - Walls set the ceiling. A furnace cannot get hotter than its wall material's melting point minus 100 degrees (and never less than 400). A Campfire tops out at 450 degrees.
The furnace heats quickly and cools slowly. It only lights fuel when there is something it can smelt. If it is hotter than the job needs it works faster, up to twice as fast at 600 degrees over.
Smelting a single piece takes 3.5 seconds and a whole block 8 seconds, at the right temperature. Metals come out as ingots. Other results come out as whole blocks once four units are ready.
Furnace walls
The material you build a Furnace from sets its top temperature:
| Wall | Melts at (degrees) | Furnace limit (degrees) |
|---|---|---|
| Limestone | 825 | 725 |
| Basalt | 1100 | 1000 |
| Bronze | 950 | 850 |
| Copper | 1085 | 985 |
| Stone, Sandstone, Marble, Slate, Clay | 1200 | 1100 |
| Granite | 1250 | 1150 |
| Steel | 1450 | 1350 |
| Concrete | 1500 | 1400 |
| Iron | 1538 | 1438 |
| Brick | 1600 | 1500 |
| Titanium Alloy | 1650 | 1550 |
| Ceramic, Porcelain | 1800 | 1700 |
| Tungsten Carbide | 2870 | 2770 |
| Tungsten | 3422 | 3322 |
| Graphite | 3600 | 3500 |
| Hexaferrum | 5000 | 4900 |
Plain stone walls stop at 1100 degrees, which is why iron (1307) needs a Furnace of brick or better. Brick is made at the Lab Bench: see Research and the Lab Bench.
Fuels
Only solid fuels go in a furnace. One unit burns for energy x 0.35 seconds, and a whole block of fuel burns four times as long as a piece.
| Fuel | Energy | Flame (degrees) | Seconds per unit |
|---|---|---|---|
| Leaves, Oak Leaves, Palm Fronds | 5 | 750 | 1.8 |
| Peat | 14 | 1020 | 4.9 |
| Palm, Willow | 14 | 1020 | 4.9 |
| Oak, Birch, Mahogany, Teak, Redwood, Bamboo | 15 | 1050 | 5.3 |
| Pine, Spruce, Ebony, Bloodwood | 16 | 1080 | 5.6 |
| Cinderstalk | 22 | 1260 | 7.7 |
| Coal | 24 | 1320 | 8.4 |
| Charcoal | 29 | 1470 | 10.1 |
| Anthracite | 30 | 1500 | 10.5 |
| Resin | 30 | 1500 | 10.5 |
| Tallow | 39 | 1770 | 13.6 |
| Beeswax | 40 | 1800 | 14.0 |
| Wax | 42 | 1860 | 14.7 |
| Magma Gland | 60 | 2400 | 21.0 |
| Helium-3 | 600 | 18600 | 210 |
| Voidsalt | 5000 | 150600 | 1750 |
Wood is enough for copper and tin. Coal, charcoal and anthracite reach iron. Make charcoal by smelting wood: 4 units of wood become 2 of charcoal at 400 degrees, so even a Campfire can do it.
What smelts into what
The yield is how much metal each unit of ore gives. A recipe for a whole block (4 units) of ore plus one unit of fuel gives about four times the yield, with fractions carried over to the next item.
| Ore | Gives | Yield | Needs (degrees) |
|---|---|---|---|
| Malachite | Copper | 55% | 922 |
| Azurite | Copper | 55% | 922 |
| Chalcopyrite | Copper | 35% | 922 |
| Cassiterite | Tin | 75% | 200 |
| Galena | Lead | 85% | 278 |
| Sphalerite | Zinc | 60% | 357 |
| Hematite | Iron | 65% | 1307 |
| Magnetite | Iron | 70% | 1307 |
| Rust | Iron | 50% | 1307 |
| Bauxite | Aluminium | 40% | 561 |
| Rutile | Titanium | 55% | 1418 |
| Ilmenite | Titanium | 30% | 1418 |
| Wolframite | Tungsten | 55% | 2909 |
| Chromite | Chromium | 45% | 1621 |
| Pentlandite | Nickel | 35% | 1237 |
| Cobaltite | Cobalt | 35% | 1271 |
| Sperrylite | Platinum | 55% | 1503 |
| Auriferous Quartz | Gold | 10% | 904 |
| Acanthite | Silver | 85% | 818 |
| Uraninite | Uranium | 80% | 962 |
| Monazite | Thorium | 10% | 1488 |
| Olivine | Magnesium | 30% | 553 |
| Dolomite | Magnesium | 13% | 553 |
| Emerald | Beryllium | 5% | 1094 |
| Pyrite | Sulfur | 50% | 200 |
| Apatite | Red Phosphorus | 15% | 502 |
| Halite | Salt | 100% | 601 |
| Kimberlite | Diamond | 2% | 3018 |
| Meteoric Iron | Star-Iron | 50% | 2890 |
Cinnabar holds Mercury, but mercury is a liquid and a furnace cannot hold liquids, so it does not smelt.
Other things a furnace makes
| Put in | Gives | Yield | Needs (degrees) |
|---|---|---|---|
| Clay | Ceramic | 100% | 900 |
| Sand, Red Sand, Quartz, Bonesand, Bloodsand, Lilac Sand | Glass | 100% | 1050 |
| Limestone | Quicklime | 55% | 619 |
| Any wood | Charcoal | 50% | 400 |
| Raw Meat, Raw Fish | Cooked Meat, Cooked Fish | 100% | 200 (a Campfire is hot enough) |
| Potato | Roast Potato | 100% | 200 |
The Electric Smelter
After the right age, the Electric Smelter heats with power instead of fuel. It uses no fuel, and it runs at up to 1800 degrees when fully powered, or as hot as its walls allow if that is lower. See The eight ages for when it opens.
Tips
- Start with copper: Malachite lies a few blocks under the ground almost everywhere, and wood is hot enough.
- Put coal or charcoal in the fuel slot for iron, and build the Furnace from Brick.
- Check the numbers in the recipe book: a missing fuel shows how hot it must burn.
- Some of the hottest jobs, such as smelting Wolframite or Kimberlite, are beyond common fuels. Tungsten also turns up as ore in the Lower Mantle: see Ores and where to find them.
- To mix metals into alloys, go to a Forge Bench: Alloys and the Forge.
← Back to the wiki · Last updated 25 October 2026. Mantlenaut is in alpha, so things change.