Bulk smelting is the single biggest optimization in Mine a Planet and the foundation of every efficient grinding session. This guide covers the 50-stack bonus, parallel queues, smelter upgrade order, and fast smelt optimization for every tier. Whether you are a brand-new player or an end-game player pushing the Astral Annihilator craft, the tips below will save you hours of smelt time every week.
For the broader smelter strategy, see our Mine a Planet smelter optimization guide. For the crafting tier progression, see our Mine a Planet crafting tier progression guide. This principle applies broadly across all progression stages and is one of the most reliable optimization levers in the game.
Tip 1: Always Queue 50-Stack Batches
The 50-stack batch size is the sweet spot for every smelter recipe. The bulk bonus applies at 25, but the maximum practical bonus is at 50. Beyond 50, the time cost of waiting on the queue offsets most of the bonus. Below 50, you miss the bonus entirely.
Most new players queue the default 10-stack batches suggested by the smelter UI, which is the worst possible setting. Switch to 50-stack immediately and you will see a 10-15% bonus on every batch. The exact mechanics vary slightly by patch, but the underlying principle remains consistent across all player playstyles.
| Batch Size | Bulk Bonus | Recommended |
|---|---|---|
| 10 | 0% | Never |
| 25 | ~5% | Overflow only |
| 50 | ~10-15% | Standard |
| 100 | ~18-22% | Overnight only |
Tip 2: Match Batch Size to Recipe Ratio
Every smelter recipe has a fixed input ratio. The optimal batch size is a multiple of that ratio, which gives you a clean output with zero leftover ore. For example, the Common Ingot recipe requires 5 Stone + 5 Copper, so a 50/50 batch produces exactly 10 Common Ingots with no leftover.
Queuing batches that do not match the recipe ratio leaves you with stranded ore. For example, a 60/40 batch on the Common Ingot recipe produces 8 ingots and leaves 20 Stone + 40 Copper stranded in your inventory. Experienced players test this approach across multiple sessions before committing to a long-term strategy based on the outcome.
Tip 3: Run Two Parallel Queues
The smelter supports two parallel queues, and most new players leave the second slot empty. Run a primary batch on slot 1 and a byproduct batch on slot 2 to keep both queues active. The total wait time is the longer of the two batches, not the sum of both.
A practical pattern is to queue the main batch (50 Iron + 25 Coal) on slot 1 and a smaller batch (25 Stardust) on slot 2. Both batches finish in parallel, and you save roughly 50% of your smelter time per cycle.
Tip 4: Upgrade the Smelter First
The smelter upgrades are higher priority than the crafting bench upgrades because the smelter affects every batch. The Smelter I upgrade is unlocked at level 5 and is the first meaningful optimization you should pursue. The Smelter III upgrade (100-stack bonus cap) is the highest-impact upgrade in the entire game.
The smelter upgrade order is Smelter I → Smelter II → Smelter III → Smelter IV → Smelter V. Each upgrade pays for itself within 2-3 grinding sessions through the time and bonus savings. Combining this insight with active pet bonuses and prestige multipliers yields compounding benefits that accelerate overall progression.
Tip 5: Save Reforges for After Smelter Upgrades
Reforges are most impactful when combined with the smelter bulk bonus. A perfect Ore Multiplier reforge on a Mythril Destroyer yields roughly 8x ore income per swing, but the bonus compounds further when the smelter bulk bonus is active. Players who reforge before upgrading the smelter miss out on the compounding effect.
The optimal order is to upgrade the smelter to Smelter III first, then invest in reforges. This ensures that every reforge campaign yields the maximum possible return. The optimal application of this strategy depends on your current biome and active pet slot configuration.
Bulk Smelt Timing Patterns
The optimal time to start a bulk smelt is 30-45 minutes before your planned logoff, because the queue needs that long to ramp up to the bulk bonus tier, and you want the timer to keep running while you sleep. A common mistake is to start the bulk smelt immediately after a long play session, when your inventory is depleted and you do not have the full 100-stack ready. The right cadence is to plan your smelt around your logoff time, not around your active play session.
A second timing pattern is to align bulk smelts with weekly events. Most weekend events grant a 2x smelt bonus, which means a 100-stack batch queued during a weekend event effectively yields 200 stacks of output. This is the single biggest bulk smelt optimization in the game, and it is why veteran players stockpile ore during the week specifically to bulk smelt over the weekend.
Bulk Smelt Pet Stack
The pet stack that maximizes bulk smelt output is a +Smelt Speed pet plus a +Ore Multiplier pet plus a +Smelt Queue Bonus pet, in that priority order. The +Smelt Speed pet directly reduces your batch time, the +Ore Multiplier pet boosts the bulk bonus itself, and the +Smelt Queue Bonus pet (which is rare) lets you run a third parallel queue on top of the standard two. Stacking all three pet bonuses yields roughly 1.6x the bulk smelt output of a player with no pet bonuses.
For players who have not yet unlocked the Epic pet slot, the two-pet combination of +Smelt Speed plus +Ore Multiplier is the priority. For more on pet combo math, see our pet combo strategy guide. For specific biome-by-biome breakdowns, see our detailed planet guides which cover each scenario in depth.
Batch Size by Ore
Different ores have different optimal batches.
| Ore | Batch | Reason |
|---|---|---|
| Common | 25-50 | Fast |
| Rare | 50 | Standard |
| Epic | 50-75 | Bonus |
| Mythic | 100 | Max |
Smelt Time Per Batch
Smelt time scales with batch and upgrade.
| Size | Base | Smelter IV |
|---|---|---|
| 25 | 30m | 22m |
| 50 | 60m | 45m |
| 75 | 90m | 67m |
| 100 | 120m | 90m |
Frequently Asked Questions
What is the bulk bonus for 50-stack?
The 50-stack bulk bonus is roughly 10-15% extra output on top of the base recipe output. The exact value varies by smelter upgrade level. This mechanic is important to master because it compounds with every other progression lever in the game economy.
Should I queue 100-stack batches?
Only if you have the Smelter III upgrade and are willing to wait for the longer queue time. The 100-stack bonus is higher but the time cost cancels out most of the benefit for active play. Generally yes, but the optimal timing depends on your current resource reserves and your active biome's node HP profile.
Can I queue more than two batches?
The default UI supports two parallel queues. Some players have reported a third queue on private servers, but this is undocumented and may be patched. Yes, but the optimal approach depends on your current progression stage and your stockpile of supporting materials.
Does the bulk bonus reset on rebirth?
No, the bulk bonus persists across rebirths along with the smelter upgrades. Yes, this works as expected, and the effect compounds with other progression systems, so the value increases over time. Veteran players typically learn to recognize these patterns within the first 10-15 hours of focused play.
What is the best batch size for the Cosmic Core recipe?
100 Void Shards + 50 Stardust in a single batch is the optimal Cosmic Core smelt cycle. The recipe produces exactly one Cosmic Core with no leftover, which makes it easy to track. Yes, this is generally the optimal choice because it maximizes the synergy with your active reforge and prestige bonuses.
Tip 6: Use Pets to Boost Smelt Throughput
The Volcano Phoenix pet grants a +25% Smelt Speed bonus that stacks with the smelter upgrades. Pairing the Volcano Phoenix with a perfectly rolled smelter setup effectively halves your smelt batch times. This is one of the highest-impact pet bonuses for players who run multiple smelt cycles per hour.
For maximum smelt throughput, pair the Volcano Phoenix with the Smelter V upgrade, a Smelt Speed pet bonus reforge, and the parallel queue technique above. The compounding effect delivers roughly 2x the throughput of a baseline smelter setup. This principle applies broadly across all progression stages and is one of the most reliable optimization levers in the game.
Tip 7: Smelt Before You Craft, Not After
A common mistake is to mine ore and immediately craft it without smelting in between. The smelter unlocks the bulk bonus, alloy recipes, and crafting milestones, so skipping the smelter means missing out on the entire progression system. Always smelt your ore into alloys before crafting.
For brand-new players, the first smelt cycle should produce Common Ingots as soon as you have 50 Stone + 50 Copper stockpiled. The Common Ingot unlocks the Copper Drill, which is your first major crafting milestone. The exact mechanics vary slightly by patch, but the underlying principle remains consistent across all player playstyles.
Tip 8: Track Your Smelt Output to Catch Bugs
The smelter's displayed output number reflects the base recipe output, not the bonus output. To catch bugs early, track your actual smelt output across batches and verify it matches the expected bonus. A typical 50/50 batch should yield 11-12 ingots, not 10. If you see 10 ingots consistently, the bonus may be disabled.
Tracking the actual output also helps you identify the optimal smelter upgrade path for your playstyle. Players who run frequent batches benefit from the time reductions, while players who run occasional batches benefit more from the bonus cap extensions. Experienced players test this approach across multiple sessions before committing to a long-term strategy based on the outcome.
Tip 9: How to Recover From a Bad Smelt Cycle
A bad smelt cycle happens when you queue batches that do not match the recipe ratio, leaving you with stranded ore. To recover, simply re-queue the stranded ore in a follow-up batch that matches the recipe ratio. The stranded ore will eventually be consumed in a properly matched batch.
If the stranded ore is significant (more than 100 units), consider salvaging it at the bench for Drill Pieces instead of waiting for a properly matched batch. Salvaging trades 1 Drill Piece per 1 unit of ore value, which is a poor exchange rate but better than letting the ore sit in your inventory indefinitely.
Tip 10: When to Switch From Common Ingot to Iron Alloy
The transition from Common Ingot to Iron Alloy happens the moment you craft the Iron Hammer. After that point, every batch you queue should be Iron Alloy or higher. Common Ingot crafting becomes obsolete once you have progressed past Mars.
Players who continue to queue Common Ingot batches after crafting the Iron Hammer are wasting time on a tier they no longer need. Switch to Iron Alloy batches immediately and your smelt throughput will improve significantly. Combining this insight with active pet bonuses and prestige multipliers yields compounding benefits that accelerate overall progression.
Tip 11: Smelter Is One of the Best Long-Term Investments
The smelter is one of the few systems that persists across rebirths and continues to provide value indefinitely. A fully maxed Smelter V setup is roughly 30-40% more efficient than a stock Smelter I setup, and the efficiency compounds across every smelt batch you run for the rest of your account lifetime.
Players who invest in the smelter early are locking in long-term value that compounds across every rebirth cycle. This is why the smelter upgrade priority is so important — investing early yields exponential returns over the long term. The optimal application of this strategy depends on your current biome and active pet slot configuration.
Tip 12: Combine the 50-Stack Bonus With Prestige Multipliers
The 50-stack bulk bonus stacks additively with the prestige multipliers. A player who has maxed the Prestige Shop Ore Multiplier upgrade and uses 50-stack batches sees roughly 3-4x the smelter throughput of a fresh-rebirth player with no prestige multipliers. For specific biome-by-biome breakdowns, see our detailed planet guides which cover each scenario in depth.
The compounding effect is most noticeable on Mythic-tier recipes like the Mythril Bar and Cosmic Core. The combination of prestige bonuses + bulk bonus + reforge bonuses yields end-game material income that would be impossible at the start of the game.
Tip 13: How Bulk Smelt Differs From Active Smelt
Active smelt means watching the smelter progress bar and reacting when a batch finishes. Bulk smelt means queuing multiple batches at once and letting the smelter process them in the background. The bulk approach is more efficient but requires careful queue management.
For most players, the bulk approach is the right choice. Queue 2-3 batches at the start of your session, and let the smelter process them while you grind on the planet. The parallel queue technique combined with bulk queuing yields the maximum smelter throughput.
Tip 14: Smelt Quality Control and Logging
Players who want to optimize their smelt efficiency should keep a log of every batch they run, including the input materials, output materials, and time taken. The log helps identify trends (e.g., which recipes have the highest bulk bonus, which times of day are most efficient for smelting).
A simple spreadsheet with columns for batch number, input, output, time, and bonus percentage is sufficient. After 20-30 batches, the log will reveal patterns that inform your smelt strategy. Veteran players typically learn to recognize these patterns within the first 10-15 hours of focused play.