The Furnace in the game Probably Stolen lets you turn Scrap Metal and Metal Ore into ingots for selling or crafting. Although it operates overnight, getting the right output depends on the materials you insert, the available power, and any installed modules. A few common input mistakes can leave the machine producing nothing.
Jump To Section:
How to Use the Furnace
Why the Furnace Isn't Working
Metal Ingot Quality Explained
Furnace Modules and Upgrades
How to Get a Furnace
Is Using the Furnace Worth It?
How to Use the Furnace in Probably Stolen
To use the Furnace, insert a charged Energy Cell and two metal materials, then leave the machine running overnight. The next morning, you can collect a Metal Ingot from its Output slot.
- Place the Furnace in your shop and open its interface.
- Insert a charged Energy Cell into the Power Source slot.
- Add two Scrap Metal, two Metal Ore, or one of each into the Input slots.
- Optionally add a Flux Smelting Agent to improve the resulting ingot.
- Finish the day and allow the Furnace to process its materials overnight.
- Open the machine the following morning and collect the Metal Ingot.
The standard Furnace requires 8 energy per night and produces one ingot from two metal materials.
There's no separate activation command needed once the machine has everything required. The smelting process occurs automatically overnight.
Can You Combine Scrap Metal and Metal Ore?
Yes. Both materials count toward the Furnace's normal two-item requirement.
You can use two Scrap Metal, two Metal Ore, or a combination of one of each. All three recipes produce a Metal Ingot, although its quality changes depending on the materials.
This makes mixed batches useful when you're short on Metal Ore but still want to improve the result compared with using only Scrap Metal.
Why Isn't the Furnace Working in Probably Stolen?
If the Output slot is empty after an entire night, check the inputs before replacing the machine or installing more modules.
The Furnace has several requirements, and an item that belongs to the smelting system doesn't necessarily count as something it can turn into metal.
You're Using Flux Instead of Metal
One particularly confusing mistake involves Flux Smelting Agent.
Flux isn't a substitute for Scrap Metal or Metal Ore. It's an additional material used to improve ingot quality.
For example, inserting two Flux Smelting Agents and a fully charged Energy Cell won't produce a Metal Ingot. You still need the required metal inputs.
If your Furnace has power but produces nothing, inspect the actual names of the materials inside it. Replace any Flux-only input setup with two valid metal materials.
Your Energy Cell Is Too Low
The Furnace needs sufficient energy for its overnight processing cycle.
An installed Energy Cell isn't enough if it lacks the charge required for the machine's current configuration.
Check the Power Source slot and the displayed energy consumption, especially if you've installed modules that alter power usage.
You're Trying to Process Junk Without the Right Module
Ordinary Junk doesn't follow the Furnace's standard Metal Ingot recipe.
You'll need the Junk Processing Module to turn Junk into usable Scrap Metal. Without that functionality, stick to Scrap Metal and Metal Ore for ordinary smelting.
If you're troubleshooting an upgraded Furnace, I'd temporarily focus on a basic two-metal batch. Once that works, you can check how each installed module changes its behavior.
How to Make Better Metal Ingots in Probably Stolen
The Furnace's output quality depends on what you put into it. Metal Ore produces a better result than Scrap Metal, while Flux and quality-focused modules can improve the finished product further.
| Materials | Ingot Quality | Value Modifier |
|---|---|---|
| 2 Scrap Metal | Low | -15% |
| 1 Scrap Metal + 1 Metal Ore | Fair | No modifier |
| 2 Metal Ore | High | +25% |
| 2 Metal Ore + Flux | Very High | +50% |
These are standard outcomes before additional module effects and market adjustments.
The most useful thing to understand is that input quality and production cost are separate concerns. An expensive batch may produce a more valuable ingot without necessarily earning more profit.
How Does Flux Smelting Agent Work?
Flux improves the purity of a Metal Ingot during smelting. It's optional, meaning the Furnace can operate without it as long as the required metal materials and power are present.
Two types of Flux Smelting Agent have been documented:
- Simple Flux Smelting Agent, which has limited uses.
- Advanced Flux Smelting Agent, which is reusable.
Flux is most useful when its quality improvement increases the final value enough to justify using it.
However, quality improvements have a limit. If your existing modules already bring the ingot to its maximum available quality, adding Flux won't necessarily improve the output further.
Best Furnace Modules and What They Do
Furnace modules allow you to change the machine's production process rather than simply making every ingot more valuable.
Some modules unlock different materials, others increase output, and some help manage power or finished quality.
Junk Processing Module
The Junk Processing Module turns six pieces of Junk into four Scrap Metal.
Because a standard ingot recipe requires two metal materials, four Scrap Metal is enough to supply two normal smelting batches.
This creates a useful production chain for players who regularly collect Junk but don't want to sell or discard it immediately.
Keep in mind that processing Junk into Scrap Metal is a separate conversion. Don't assume that inserting Junk directly into the standard Furnace recipe will automatically produce ingots.
Blast Module
The Blast Module changes the production ratio from two metal inputs for one ingot to three metal inputs for two ingots.
That means two standard ingots normally require four metal inputs, while a Blast-assisted batch can produce two from three.
The disadvantage is reduced output purity, so the extra ingot doesn't always translate into the best possible sale value.
This module is worth considering when your goal is to produce more ingots from a limited supply of materials, particularly if you have other ways to improve their quality.
Quality and Efficiency Modules
Quality modules improve the grade of your Metal Ingots. With sufficient upgrades, ingots can reach Perfect quality and much higher value modifiers.
Efficiency modules reduce power consumption, making the Furnace easier to operate alongside other machines that need Energy Cells.
I'd prioritize the upgrade that addresses your actual limitation. If electricity is plentiful but your ingots sell for very little, better quality is worth considering. If your shop struggles to power its equipment every night, efficiency may be more useful.
How to Get a Furnace in Probably Stolen
Dr. Jackson is the main source of Furnaces. You can find the machine through his shop, and he can also introduce it during the early stages of a story-mode playthrough.
Because the available descriptions differ on the exact terms of the early offer, it's best to check Dr. Jackson's inventory and any offer he makes during your run rather than rely on a fixed acquisition price.
You don't need to unlock a separate smelting profession to operate the machine.
Once you have a Furnace, you can begin with Scrap Metal acquired through scavenging or trading. Metal Ore is another option, including supplies obtained through the GP Mining Coop after the relevant introduction.
Is the Furnace Worth Using in Probably Stolen?
The Furnace is useful because it can turn materials you already have into Metal Ingots, which can be sold or used in other crafting processes.
But the best material for producing a valuable ingot isn't necessarily the best material for maximizing profit.
Compare Input Costs Before Choosing a Recipe
As an example, consider a hypothetical batch where an ingot's starting value is 50 Credits.
With the standard quality modifiers, two Scrap Metal produce an ingot valued at 42.5 Credits, while two Metal Ore produce one valued at 62.5 Credits, before other price changes.
That's 20 Credits in additional gross value from the higher-quality material combination.
However, if obtaining the two Metal Ore costs you more than 20 Credits extra compared with Scrap Metal, the higher-quality recipe may not actually be more profitable.
The same logic applies to Flux. Paying for an additive only makes sense if the extra value you obtain justifies its cost.
Should You Sell Metal Ingots or Save Them?
Metal Ingots aren't limited to direct sales. They can also supply crafting equipment, including production that requires metal materials.
That gives you two possible uses for a Furnace: creating products for immediate sale or preparing materials for another part of your business.
I'd keep a reserve of ingots if you expect to use them for crafting. Selling everything can leave you buying back materials later when you need them.
For a shop focused on resale, prioritize affordable inputs and reliable overnight production. For a crafting-focused shop, consistent access to Metal Ingots may matter more than squeezing the highest sale value from every batch.
Ultimately, the Furnace is most useful when you understand what each input produces, how its modules change the process, and whether the resulting ingot is worth more to you as merchandise or as a crafting material.
