If you have ever wondered why your Mine a Planet smelter feels slow even though you are queuing ore constantly, the answer almost always lies in batch sizing and queue priority. The smelter is one of the most under-optimized systems in the entire game, and a player who understands the 50-stack bulk bonus, parallel alloy conversions, and byproduct ratios will out-grind their peers by a factor of three or four within just a few hours. This guide walks through every lever in the smelter interface, explains the math behind the bonus tiers, and shows you the exact queue order to use from your first Common Ingot all the way to your first Cosmic Core.
The reason this matters so much is that the smelter is the bottleneck of the entire mining loop. Even with the strongest drill head, if your ingots are stuck in a 10-stack queue, you cannot craft the next tier of drill in time to push into the next planet. Smarter smelting is what separates players who are stuck on Earth for three days from players who are already clearing Nebula by the end of their second session.
Understand the Bulk Bonus Tiers
The smelter applies a hidden bonus based on the size of the batch you queue, and the bonus scales in clear tiers. The default suggested batch size of 10 grants no bonus at all, which is why so many beginners feel like the smelter is punishing them. Once you start queuing 25 of the same ore, a small bonus kicks in. At 50, the bulk bonus hits its sweet spot and adds roughly 10-15% extra output. At 100, the bonus grows further, but the time penalty for waiting on the queue cancels out most of the upside unless you are doing overnight batches.
| Batch Size | Bulk Bonus | Time Cost | Recommended For |
|---|---|---|---|
| 10 | 0% | Fast | Never (avoid) |
| 25 | ~5% | Medium | Low-tier overflow only |
| 50 | ~10-15% | Slow | Standard for every recipe |
| 100 | ~18-22% | Very slow | Overnight bulk smelt only |
The numbers above are derived from community testing across the UPDATE1 patch and may shift with future balance changes. For absolute certainty, observe your own smelter output after each batch and log the bonus in a personal spreadsheet. The exact value of the bulk bonus is the single most volatile mechanic in Mine a Planet, and only your own data will tell you what to expect on the day you queue it.
Queue in Parallel, Not in Series
The single biggest optimization is to run two batches at the same time. The smelter supports parallel queues, and many players waste this capability by queuing one batch at a time and waiting for it to finish before starting the next. The correct approach is to queue your main batch — say, 50 Iron Ore — and immediately queue a secondary batch of 25 Coal on the adjacent slot. Because both batches progress simultaneously, your total wait time is roughly the same as the longest single batch, not the sum of both.
For the early game, the standard parallel queue is 50 Stone plus 50 Copper, which produces two streams of Common Ingots simultaneously. For the mid game, swap to 50 Iron Ore plus 25 Coal for the Iron Alloy recipe, since the byproduct ratio aligns perfectly. For the late game, the standard is 50 Mythril Ore plus 25 Stardust, which produces Mythril Bars at maximum efficiency. The point is that parallel queuing is not a luxury — it is the only way to keep your crafting bench fed.
Match the Batch Size to the Recipe Ratio
Every alloy recipe has a fixed input ratio, and queuing batches that do not align with that ratio leaves you with stranded ore. The most common beginner mistake is smelting 100 Iron Ore into 100 Iron Ingots, then realizing the Iron Alloy recipe needs 10 Iron Ingots plus 5 Coal per craft, which means you are constantly short on Coal. Instead, queue in batches that match the recipe ratio and only smelt more of the input that is currently short.
| Alloy | Ore Ratio | Recommended Queue | Output |
|---|---|---|---|
| Common Ingot | 5 Stone + 5 Copper | 50 Stone + 50 Copper | 10 Common Ingots |
| Iron Alloy | 10 Iron + 5 Coal | 50 Iron + 25 Coal | 5 Iron Alloys |
| Titanium Plate | 20 Titanium + 10 Coal | 100 Titanium + 50 Coal | 5 Titanium Plates |
| Mythril Bar | 50 Mythril + 25 Stardust | 100 Mythril + 50 Stardust | 2 Mythril Bars |
| Cosmic Core | 100 Void Shards + 50 Stardust | 100 Void Shards + 50 Stardust | 1 Cosmic Core |
Notice how every recommended queue size is a multiple of the recipe ratio. This is intentional — when the queue finishes, you have exactly the materials you need to craft, with zero leftover. For more advanced players who want to push into bulk overnight smelt, our Mine a Planet crafting guide breaks down every recipe including the rare Epic and Mythic alloys.
Upgrade the Smelter Bench as Soon As Possible
The smelter bench itself has upgrade levels that reduce the time per batch and increase the bulk bonus cap. The first upgrade costs Common Ingots and a small amount of Drill Pieces, and it cuts roughly 10% off every batch time. The second upgrade requires Iron Alloy and is significantly more expensive, but it cuts another 15% off the batch timer. By the time you reach the Mythril-tier smelter upgrade, batch times are roughly half of what they were at the starter bench, which makes overnight 100-stack batches viable.
| Upgrade Level | Cost | Batch Time Reduction | Bulk Bonus Cap |
|---|---|---|---|
| Smelter I | 50 Common Ingots + 500 Drill Pieces | 10% | 50-stack only |
| Smelter II | 25 Iron Alloys + 2,500 Drill Pieces | 15% | 75-stack unlocked |
| Smelter III | 10 Titanium Plates + 10,000 Drill Pieces | 20% | 100-stack unlocked |
| Smelter IV | 5 Mythril Bars + 50,000 Drill Pieces | 25% | 100-stack + speed boost |
| Smelter V | 3 Cosmic Cores + 250,000 Drill Pieces | 30% | 100-stack + rare drop chance |
The exact upgrade costs and reductions are based on community-reported values and may be tweaked by the developers in future patches. The general direction — higher upgrades unlock larger batch sizes and shorter timers — has remained stable across multiple updates, however.
Reforge a Drill Before Smelting Mythic Ores
Reforging is the system that lets you reroll the secondary stats on a drill head, and one of the most overlooked reforge bonuses is the +Smelt Speed stat, which reduces the time of every batch by a small percentage. A drill that rolls +Smelt Speed twice can cut 20% off your total smelter time, which compounds massively across the hundreds of batches you will run during end-game Void grinding. If you are about to smelt thousands of Mythril Ore into Mythril Bars, reforge your active drill to maximize Smelt Speed first.
The Reforge station costs Drill Pieces per attempt, and the cost scales with the drill tier. A Wooden Pickaxe reforge is essentially free, while a Mythril Destroyer reforge can cost hundreds of thousands of Drill Pieces per roll. The smart play is to reforge early and often on your starter drills until you understand the stat pool, then save your high-tier reforges for drills you intend to keep across multiple rebirths.
Save Smelter Batches for Overnight Play
The single biggest optimization that most players miss is treating the smelter as an overnight queue, not a real-time system. The reason is that the 100-stack bonus tiers only become profitable when you let the queue run uninterrupted for 4-8 hours, which is exactly what happens while you sleep. A player who queues a 100-stack batch before bed and wakes up to find 18-22% extra Mythril Bars is operating at roughly 1.5x the smelter throughput of a player who queues the same ore in 50-stack batches throughout the day.
To get the most out of overnight smelting, pre-stage your smelter queue 30 minutes before you log off, and make sure both the smelter upgrade and the active drill's reforge bonuses are aligned for maximum batch time reduction. A Smelter IV upgrade plus a perfectly rolled +Smelt Speed drill can cut a Mythril Bar batch from 4 hours to roughly 2.5 hours, which means you can fit 2 full overnight batches instead of 1. For more detailed overnight smelter math, see our bulk smelt bonus guide.
Common Smelter Bottlenecks and Fixes
The most common smelter bottleneck is inventory overflow, where your drill is producing ore faster than your smelter can consume it. The fix is to slow down the drill by switching to a lower-tier drill for a few minutes, which gives the smelter time to drain. The second most common bottleneck is recipe ratio mismatch, where you queue 100 Iron Ore but the Iron Alloy recipe only consumes 10 Iron Ingots per craft, leaving 50 Iron Ingots stranded in your inventory. The fix is to always queue in multiples of the recipe ratio, which our smelter recipes guide details for every alloy.
The third bottleneck is parallel queue confusion, where players accidentally queue two batches of the same recipe and wait twice as long for half the throughput. The fix is to always queue two different recipes in parallel — Iron Alloy plus Coal Smelt, Mythril Bar plus Stardust Smelt, and so on — which keeps the smelter fully utilized without the wasted overlap.
Frequently Asked Questions
Does the 50-stack bonus work on every smelter recipe?
Yes, the bulk bonus applies uniformly to every recipe in the game, from Common Ingot through Cosmic Core. The exact bonus value is consistent across tiers, but the absolute number of bonus ingots grows as the recipe tier increases, which means the bulk bonus is most valuable when applied to late-game recipes.
Can I queue more than two batches at the same time?
The default UI supports two parallel queues. Some players have reported being able to add a third batch using a private server, but this behavior is not officially documented and may be patched out at any time. For reliability, stick to the standard two-queue system.
Should I smelt overnight or in shorter bursts during play?
If your smelter is upgraded to Smelter III or higher and you can commit to a 100-stack queue, overnight bulk smelting is the most efficient use of time. During active play, 50-stack batches aligned with the recipe ratio are usually the right call.
What happens to leftover ore when the recipe ratio does not divide evenly?
Leftover ore stays in your inventory until you queue it again. The only way to avoid stranded ore is to queue batches that match the recipe ratio exactly, which is why the recommended queue sizes in the table above are all multiples of the recipe inputs.
Is the bulk bonus affected by Prestige Points?
Yes. The Ore Multiplier prestige upgrade stacks with the bulk bonus, so a high-prestige player sees a noticeably larger ingot output per batch than a fresh-rebirth player. The bonus is multiplicative, which means the combination of prestige + bulk is what drives end-game smelt throughput.
Use Pets to Push Smelter Output Even Higher
The smelter is not the only system that affects how fast your ingots pile up — pets with the +Smelt Speed passive can compound your bulk bonus significantly. The Volcano Phoenix is the most notable smelt-boost pet because it grants a flat +Smelt Speed bonus that stacks additively with the smelter upgrade bonuses, which means a player who has both the Smelter IV upgrade and a perfectly rolled Volcano Phoenix can hit smelt times that are nearly half of what a fresh-rebirth player can manage. Pairing the pet with the Volcano planet grind is also thematic, since the pet drops most frequently from the Volcano biome.