Blue science is the first real complexity spike in Factorio. It's not just about adding a new ingredient — it introduces fluids, cracking, and multi-step production chains. I've seen countless factory tours stall right here because the oil setup wasn't thought through.
Recipe and Requirements
Each chemical science pack needs three components:
Engine
Circuit red
Sulfur
Chemical scienceTwo of these three require oil products. Red circuits need plastic (petroleum + coal). Sulfur needs petroleum gas and water. That means you can't automate blue science until you have a working oil refinery setup.
Oil Refining — The Hard Part
Here's the chain from well to blue science:
| Step | Input | Output | Machine |
|---|---|---|---|
| Oil extraction | Crude oil | Crude oil | Pumpjack |
| Basic refining | Crude oil | Heavy, Light, Petroleum | Refinery |
| Sulfur | Petroleum + Water | Sulfur | Chemical plant |
| Plastic | Coal + Petroleum | Plastic bar | Chemical plant |
| Red circuits | Plastic + Copper + Green | Red circuit | Assembler |
| Engine | Steel + Gear + Pipe | Engine unit | Assembler |
| Blue science | Engine + Red circuit + Sulfur | Blue pack | Assembler |
The critical path is petroleum. You need enough refineries producing petroleum gas to feed both plastic and sulfur production.
Optimal Ratios for 5 SPM
Here's the ratio that works for a stable 5 blue science per minute setup:
| Component | Machines | Notes |
|---|---|---|
| Blue science assemblers | 5 | Target output rate |
| Engine unit assemblers | 2 | Each feeds about 2.5 science assemblers |
| Sulfur chemical plants | 1 | One plant supplies ~10 science assemblers |
| Plastic chemical plants | 2 | Steady supply for red circuits |
| Refineries (basic) | 1-2 | One refinery provides enough petroleum for this scale |
| Red circuit assemblers | 1 | For blue science modules |
| Copper wire assemblers | 1 | Feeds red circuits (if not already on bus) |
Layout — Compact Blue Science Cell
A compact blue science array fits in roughly 15×30 tiles. Here's the layout pattern:
The engine assemblers sit next to the bus, pulling steel, iron, gears, and pipes. The sulfur plant takes petroleum from the pipe and outputs to a belt. Red circuits come from an existing production line.
Transitioning to Advanced Oil Processing
Once you research advanced oil processing, your refinery setup changes significantly:
| Aspect | Basic | Advanced |
|---|---|---|
| Crude per cycle | 100 | 100 + 50 Water |
| Heavy oil output | 30/s | 50/s |
| Light oil output | 30/s | 50/s |
| Petroleum output | 40/s | 30/s |
| Cracking needed | No | Yes |
The catch with advanced processing: it produces more heavy and light oil but less petroleum. You need cracking (heavy→light→petroleum) to balance the outputs. Without cracking, your refineries stall from heavy oil backup.
Common Pitfalls
Heavy oil backup. Advanced refining without cracking. The refineries fill up with heavy oil, stop producing, and suddenly your entire base runs out of plastic. Solution: crack heavy oil to light, and light to petroleum. Use a circuit condition to only crack when heavy > 1k.
Running out of water. Sulfur and advanced refining both consume water. A single offshore pump feeds about 10 chemical plants. If your sulfur production stalls, check water first.
Petroleum vs. plastic balance. One plastic bar needs 20 petroleum gas. At 5 SPM, you need roughly 10 plastic per minute. That's one chemical plant running full time. If red circuit production backs up, plastic is the bottleneck — not copper.
Scaling Blue Science
To go from 5 SPM to 30 SPM:
- Add more refineries (6-8 with advanced + cracking)
- Scale up to 30 blue science assemblers
- Add more engine and sulfur production
- Upgrade belt tiers to keep up with throughput
The refinery setup scales linearly. With advanced processing and cracking, 8 refineries plus 1 heavy→light and 7 light→petroleum crackers provide perfect balance for large-scale production.
Bottom Line
Blue science is the first multi-fluid production chain in Factorio. The key takeaway: petroleum is always the constraint. Build more refineries than you think you need, set up cracking before your tanks fill with heavy oil, and keep water flowing.
Numbers to remember:
- 2 refineries minimum for 5 SPM
- 1 engine assembler per 2.5 science assemblers
- Petroleum demand = plastic (20/s) + sulfur (30/s) per chemical plant
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