Quick Answer
Slag is the regular byproduct created when a Shaker processes Wet Sand in Sandustry. It must be ignited to have a chance to become Burnt Slag, which can then be dropped onto a Kinetic Slag Press to produce Gold and Spores. Because the burning step is probabilistic and the Press can be blocked by bad inputs, a good line needs overflow space and a way to clear jams.
The safest mental model is a three-stage refinery: separate, burn, then impact-process. Keep the Gold outlet from the Shaker distinct from the Slag path, and do not send ordinary Slag directly to the Press. A visible buffer between stages makes random yield and transport failure easier to diagnose.
Where Slag Comes From
The official Wet Sand page says a Shaker consumes Wet Sand and produces Slag, with Gold also possible from that processing step. Gold falls through the Shaker while Slag remains on top and is pushed toward the Shaker's facing direction. This built-in separation is useful only if the structure has enough space on both sides for outputs to move.
Wet Sand itself comes from Sand touching Water, so a Slag shortage may begin upstream. Check the Water contact zone, the Wet Sand feed, and the Shaker surface before adding more burning equipment. If ordinary Sand, loose solids, or an oversized pile blocks the path, the later refinery stages cannot compensate.
| Stage | Input | Confirmed output | What to watch |
|---|---|---|---|
| Mixing | Sand plus Water | Wet Sand | Uncontrolled Water consumption |
| Shaking | Wet Sand on a Shaker | Slag and possible Gold | Slag leaving the top slowly |
| Burning | Slag plus ignition | Burnt Slag or destroyed material | Random yield and spreading Fire |
| Impact processing | Burnt Slag dropped onto a Kinetic Slag Press | Gold and Spore | Minimum fall and surface blockages |
Burning Slag Without Losing Control
The official Burnt Slag page says Slag can be ignited manually with a Flamethrower or suitable Rocket Launcher upgrade, or automatically over Lava trapped in Filters. It also states that burning does not guarantee Burnt Slag; some input is destroyed without output. Design storage and expectations around variable results rather than a fixed one-to-one conversion.
A manual burn pit is simpler to inspect while learning the chain. Use nonessential walls, leave a controlled output route, and avoid placing Water, Cinder, or plant material where Fire can trigger extra reactions. Once the flow is stable, a contained Lava heat cell can remove the repeated manual ignition step.
Use this commissioning sequence:
- Run the Shaker briefly and confirm Slag exits on the intended side.
- Collect a small buffer away from other flammable materials.
- Ignite the test batch and observe where surviving Burnt Slag settles.
- Move only Burnt Slag toward the Press input.
- Add overflow and jam access before increasing production.
Processing Burnt Slag
Burnt Slag is the correct input for the Kinetic Slag Press. The official Press page says the material must fall onto the Press from sufficient height to transform; anything else, including a bad input or an inadequate drop, can remain on top and block following material. The official page gives a specific threshold, but version-sensitive layout measurement should still be checked in the current Early Access build.
The Press does not include a conveyor surface like the Shaker. Its official tips suggest angled Launchers along the top to move stagnant pixels away without interrupting material that is still falling. Whether a particular compact launcher pattern works with your current patch is Pending confirmation, so test with a small stream and keep manual clearing access.
Diagnosing a Stalled Slag Line
When output stops, trace the line from the end backward. Check whether the Press surface is blocked, whether Burnt Slag has enough drop, whether the burn stage is receiving normal Slag, and whether the Shaker has Wet Sand. This sequence avoids rebuilding a working upstream section because of a single wrong pixel at the final machine.
If Fire keeps dying out, increase safe buffer continuity rather than introducing Lava into an unprepared area. If too much normal Slag reaches the Press, add physical separation between the burn chamber and the drop tower. If Water reaches the heat cell, repair the liquid boundary first because Lava-Water contact creates Steam and changes the intended setup.
Balancing Buffers Across the Chain
The Shaker, burn area, and Kinetic Slag Press do not behave like three identical timed machines. The Shaker separates material and moves Slag slowly across its top, burning has a variable result, and the Press requires the correct input to arrive with a valid fall. A buffer between each stage prevents one difference from immediately blocking every earlier process.
Use the first buffer to show whether Wet Sand processing is keeping up with the mixer. Use the second to separate ordinary Slag waiting to burn from Burnt Slag ready for impact processing. Neither buffer needs a universal numeric target: it needs visible boundaries, overflow space, and an access point for clearing the wrong material.
Do not read a large Slag pile as proof that the Shaker should be expanded. It may instead show that the burn zone is too small, Fire is not reaching the material, or surviving Burnt Slag has nowhere to go. Likewise, an empty Press does not prove low production until the drop route and surface have been inspected.
A Clean Test for Each Stage
Test the Shaker with a limited Wet Sand batch and verify that Gold and Slag leave on their documented sides. Test burning in isolation and separate surviving Burnt Slag from ordinary input before measuring anything downstream. Finally, drop only confirmed Burnt Slag onto a cleared Press and watch both its top surface and lower output.
This sequence avoids treating the official reaction chain as an assumed throughput formula. Burning has a random outcome, while obstruction and fall conditions can invalidate a Press test. Exact rates, buffer sizes, and a best tower height beyond the documented requirement are Pending confirmation for the current build and should be recorded locally.
Sources
- Sandustry Official Wiki — Wet Sand
- Sandustry Official Wiki — Burnt Slag
- Sandustry Official Wiki — Kinetic Slag Press
- Sandustry Official Wiki — Lava
Sandustry is developed by Lantto Games and published by Hooded Horse. This independent guide is not affiliated with or endorsed by the developer, publisher, Valve, or Microsoft.