Casting and Smelting: Lava to Molten Metals Guide

If you’ve reached Vulcanus or you’re trying to decide whether to keep smelting the old way or switch to molten metals, this is the point where your production line either gets simpler or turns into a bottleneck hunt. The good news is that the path is straightforward: use the Foundry, decide whether you are feeding it ore or lava, and then use molten metals first to stabilize plates before you chase the more specialized casting recipes. Do that in the right order and you’ll avoid the most common mistake: trying to build a fancy casting hub before your calcite, fluid handling, and output belts can actually keep up.

Decide whether you are smelting ore or casting from lava

Start by choosing your feedstock, because that choice changes your entire layout. Molten iron can be made from Iron ore×50 + Calcite×1 → Molten iron×500 in 32s, or from Lava×500 + Calcite×1 → Molten iron×250 + Stone×10 in 16s. Molten copper follows the same pattern: Copper ore×50 + Calcite×1 → Molten copper×500 in 32s, or Lava×500 + Calcite×1 → Molten copper×250 + Stone×15 in 16s. Use the ore route when you already have ore available and want the larger molten output batch. Switch to the lava route on Vulcanus when you want local production and are happy to take the smaller molten output plus stone byproduct.

Calcite is not a side input you sprinkle in later; both molten-metal routes depend on it, so make sure your calcite logistics are solved before you scale the line. That matters even more on Vulcanus, where lava is a fluid found on the planet and cannot be barreled or shipped to other planets. Build your plan around local processing, not export.

Here is the quick reference you should keep in mind while setting up the first line:

Set up your first foundry line before chasing fancy casting recipes

Once molten metal is flowing, do not jump straight into niche recipes. First, cast molten iron and molten copper back into plates and make sure the line is stable. Casting iron is Molten iron×20 → Iron plate×2 in 3.2s, and Casting copper is Molten copper×20 → Copper plate×2 in 3.2s. That gives you a clean baseline for belt speed, buffer size, and demand before you feed the molten stream into more specialized recipes.

This step is important because the old fallback is still simple and familiar. A Stone furnace is the basic, low-cost starting furnace, and it processes Iron plate, Copper plate, and Stone brick at 0.3125 per second, with Steel plate at 0.0625 per second. It is the right early setup, but it is also only half the speed of a Steel furnace or Electric furnace for iron, copper, and stone brick, and half the speed for steel as well. Use Stone furnaces when you need a cheap baseline; replace them when your throughput demands stop fitting that pace. The practical move is to let Foundries produce plates, compare them to your old furnace output, and only then decide how much of your smelting block to convert.

Use direct casting when it replaces an extra machine step

After your plate line is stable, start cutting out unnecessary machine hops. If the next product is a simple intermediate, cast it directly from molten metal instead of making plates first and assembling later. Casting copper cable is Molten copper×5 → Copper cable×2 in 1s. Casting iron gear wheel is Molten iron×10 → Iron gear wheel×1 in 1s. Casting iron stick is Molten iron×20 → Iron stick×4 in 1s. Casting pipe is Molten iron×10 → Pipe×1 in 1s.

That is the rule you should follow: if a recipe lets you skip a plate step, use it. It simplifies your layout, reduces the number of machines you need to feed, and keeps high-volume parts moving without clogging a separate plate belt first. Molten copper can also be cast directly into copper cables or low density structure, and many casting recipes are more resource efficient than casting to plate and then using an assembling machine. So do not build the longer chain by habit; build the shorter chain when the recipe allows it.

Build around the real bottleneck: fluid supply and transport

The first thing to solve is not the Foundry count, but the fluid network. Molten iron and molten copper cannot be placed into barrels, so they cannot be sent to other planets. Treat them as local fluids, not portable commodities. On Vulcanus, that means keeping your source, Foundries, and fluid handling close enough that pipes and unloading stay simple.

If you need longer-distance movement inside a local production area, use fluid wagons. That is why fluid logistics are the right answer for large Vulcanus builds. Do not try to force molten metals into an item logistics model; build around pipes and wagons instead. Also remember that Lava is exclusive to Vulcanus and is extracted from lava lakes via an offshore pump, so your entire metal front end should be designed as a planet-local industrial block.

Expand into high-value products only after your base molten line is stable

Once molten iron and molten copper are flowing reliably, you can move into higher-value mixed recipes. The one to aim for is Casting low density structure, which uses Molten iron×80, Molten copper×250, Plastic bar×5 → Low density structure×1 in 15s. Do not rush into it before your base line is steady. You need reliable molten supply first, and you need a firm plan for plastic bars before you start scaling low density structure. If either input is shaky, the whole recipe becomes an expensive stall.

On Vulcanus, make a point of using the byproducts instead of ignoring them. Lava-based molten copper produces Stone×15, and lava-based molten iron produces Stone×10. Stone is valuable: it is used for stone furnaces, rails, landfill, and can be smelted into stone bricks. A Stone furnace can make Stone brick from Stone×2 → Stone brick×1 in 3.2s. Route the stone byproduct into bricks or other stone needs so it becomes part of your build instead of filling buffers and creating cleanup problems. If you let it pile up, you are wasting one of the most useful secondary outputs in your Vulcanus factory.

The right progression is simple: get calcite and lava or ore flowing, cast plates, replace extra machine steps with direct casting where possible, and only then expand into low density structure and other mixed products. If you do it in that order, molten metals stop being a novelty and become the backbone of a much cleaner factory.