Sandustry Slag Processing Guide: From Wet Sand to Gold

Why Sandustry Slag Matters for Your Factory

If you've spent any time building automated factories in Sandustry, you already know that Sandustry slag is one of the most important intermediate resources in the game. It sits at the crossroads of your production chain, bridging raw material extraction and valuable output generation. Understanding how to efficiently process Sandustry slag can mean the difference between a smooth-running operation and a frustrating pile of unconverted material.

Slag processing involves multiple stages — from shaking wet sand to burning slag with a flamethrower, and finally pressing it into gold and spores using the Kinetic Slag Press. Each stage introduces unique physics-based challenges that require thoughtful engineering to overcome. Let's break down everything you need to know.

Understanding the Slag Production Chain

The slag production chain in Sandustry follows a multi-step process. Each transformation changes the material's properties, density, and value. Here's how the full pipeline works:

Step 1: Wet Sand to Slag via Shakers

The first stage involves feeding wet sand (also called red sand) into Shakers. These machines vibrate the sand and gradually convert it into slag and gold particles. Based on player experience shared in community tutorials, a setup of approximately 10–12 Shakers is sufficient as long as you maintain only a single layer of wet sand coming through the input.

The critical challenge here is filtering. Sandustry's filter mechanics only check one block above the filter, which means if material piles up, unwanted elements can slip through. To prevent this:

• Create a bottleneck that forces all material into a single-block-wide channel before filtering
• Use filters set to "block wet sand" on a secondary path to redirect unwanted materials
• Place a dedicated filter allowing only wet sand vertically (like a gate) on the Shaker input

Step 2: Burning Slag into Burnt Slag

Once you have slag, the next step is to burn it. You'll need to unlock the flamethrower from the Tools tech tree. When you set slag on fire, it slowly catches and transforms into burnt slag.

One important property change: burnt slag is significantly less dense than regular slag. A pile that occupied six blocks of space may compress to fewer than two blocks after burning. This density reduction is beneficial for storage but introduces throughput considerations when feeding it into the next stage.

Step 3: Kinetic Slag Press for Gold and Spores

The Kinetic Slag Press is where the magic happens. Drop burnt slag into the press's green activation zone, and it converts the material into gold and spores. However, this machine has a strict processing limit — it can only handle a certain amount of slag at a time.

Common Challenges with Slag Processing

The physics-based nature of Sandustry means that material flow can be unpredictable. The most widely reported issue in the community involves pile-ups at the Kinetic Slag Press. When too much burnt slag drops simultaneously, particles land on top of each other instead of hitting the press, creating blockages that require manual clearing.

Community reports from the Sandustry Steam Community discussions highlight that this is a widespread frustration. Multiple players have independently arrived at similar solutions, which we'll cover in detail below.

Proven Solutions for Slag Press Pile-Ups

The Filter Slow-Feed Method

The most consistently recommended solution across the community is using filters to throttle input flow. Filters in Sandustry naturally limit how quickly material passes through them, which makes them perfect for controlling the feed rate into the Kinetic Slag Press.

Here's how players set this up:

• Place a filter at the top of the drop chute, set to allow only burnt slag through
• Space multiple filters vertically — some players use 4 filters spaced a couple of blocks apart
• The filters slow throughput so particles never stack on top of each other
• Filters also ensure a straight vertical drop, preventing particles from bouncing onto others

One player reported that after implementing this setup, they "didn't ever have to look at it again for an entire playthrough." Another confirmed that a single row of filters set to burnt slag was all they needed for a stable, unjammable system.

The Launcher Overflow Method

An alternative approach combines filters with launchers:

This dual-layer approach handles both the input throttling and the cleanup if any material fails to convert. The launchers at the bottom actively push away any slag that didn't get processed, preventing it from building up and blocking the press.

Compact Two-Press Splitter Build

For players wanting higher throughput, a dual-press setup with a splitter can work well. The splitter divides material based on height — bottom-layer material goes to one press, top-layer to the other. Key design considerations include:

• Limit headroom above the launcher to reduce throw distance and naturally slow output
• Add a filter after the launcher to further throttle flow
• Ensure spore drainage is fast enough to prevent backup above the press
• Use the natural weight difference between gold (heavier) and spores (lighter) to your advantage

Filter Mechanics Deep Dive

Filters are arguably the most versatile tool in your slag processing arsenal. Understanding their quirks is essential for any efficient build.

How Filters Actually Work

A critical mechanic to remember: filters only check one block above them. If material stacks higher than one block, the filter won't detect what's on top. This is why creating a bottleneck that compresses material to a single layer before filtering is so important.

Using Filters as Output Gates

An clever trick for compact Shaker setups involves placing a filter on the output side, set to allow only slag through. This prevents unprocessed wet sand from escaping the Shaker area. The sand piles up until it converts to slag, at which point it passes through the filter. While slower than a long Shaker array, this method enables much more compact designs.

Splitter Designs for Even Distribution

When processing large volumes of slag, you'll eventually need to split material between multiple processing lines. Here are the main approaches:

Method 1: Dual Launcher Split

The simplest method uses two launchers pointing in opposite directions. However, this design has a known flaw: input from one side gets prioritized by one launcher, creating uneven distribution. This works acceptably when drawing from a large container but struggles with continuous flow.

Method 2: Launcher-with-Cap Split

A more balanced design, reportedly originating from the Sandustry Discord community, involves a launcher firing straight up with a block placed directly above it at the top of its arc. Material hits the block and falls off evenly to both sides. Conveyor belts on either side catch the distributed material. While not perfectly 50/50, it provides significantly more even distribution than the dual-launcher method.

FAQ

What is Sandustry slag and how do I produce it? Sandustry slag is an intermediate resource produced by feeding wet sand (red sand) into Shakers. The Shakers vibrate the sand and convert it into slag and gold particles. You'll need approximately 10–12 Shakers for efficient processing, and proper filtering on both input and output sides to prevent contamination.

Why does my Kinetic Slag Press keep getting jammed? The most common cause is feeding burnt slag too quickly. The press can only process a limited amount at a time, and excess material piles on top instead of being converted. Community-tested solutions include placing filters set to "burnt slag only" at the top of your drop chute to slow the feed rate, and adding launchers at the bottom to clear any unconverted material.

How do I separate gold from spores after pressing slag? Gold is naturally heavier than spores in Sandustry's physics system, so it will sink to the bottom of any pile. You can use this to your advantage by placing a filter set to allow only spores through on the upper layer, while gold collects below. For safer operation, limit the material to a single-block height before filtering, though two-block heights can also work.

Can I make a compact slag processing system? Yes. By using output-side filters set to allow only slag through, you can create a compact Shaker setup that processes material more slowly but in a much smaller footprint. For the burning and pressing stages, combining a height-based splitter with throttled launchers and filters enables a space-efficient dual-press design that handles steady throughput without jamming.