Pathfinder Alchemy Rules
Alchemy in Pathfinder is one of the game's most mechanically layered systems — a crafting and combat framework that rewards players who plan ahead and punishes those who improvise badly. This page covers how the Alchemist class interacts with the Crafting skill, how Quick Alchemy and Advanced Alchemy function as distinct subsystems, and where the rules draw hard lines that trip up even experienced players.
Definition and scope
The Alchemist class, introduced in the Pathfinder Second Edition Core Rulebook (Paizo Publishing), is built around the creation and use of alchemical items — bombs, elixirs, mutagens, and poisons — without the spell-slot economy that governs other magic-adjacent classes. Instead, the Alchemist runs on resonance with the Craft skill and a daily resource called reagents.
Reagents are the fuel. Every Alchemist receives a number of "batches of infused reagents" each day equal to their level plus their Intelligence modifier. These reagents are not physical inventory — they represent the character's trained intuition about improvised formulas. Unused infused reagents expire at the next daily preparation. That expiration is not optional and not negotiable under the published rules.
The scope of the Alchemist's toolkit is defined by their formula book, which works analogously to a wizard's spellbook. A formula must be in the book before it can be crafted. The Core Rulebook grants Alchemists 4 starting formulas from the Alchemist list, and additional formulas can be acquired through leveling, downtime Crafting, or finding written formulas in the world.
How it works
The system splits into two distinct modes, and confusing them is the single most common rules error at Pathfinder tables.
Advanced Alchemy happens during daily preparations. The Alchemist spends batches of infused reagents — 1 batch per item, unless modified by a class feature — and produces a set of items before the session begins. These items are infused, meaning they carry a 24-hour expiration. A 5th-level Alchemist with an Intelligence modifier of +3 starts each day with 8 batches, producing up to 8 items through Advanced Alchemy, or fewer if some batches are reserved for Quick Alchemy.
Quick Alchemy is the in-combat option. As a single action, an Alchemist spends 1 batch of infused reagents and 1 gold piece worth of base materials to produce 1 alchemical item from their formula book. That item is immediately usable but expires at the start of the Alchemist's next turn if unused. The gold piece cost is often overlooked at tables — the rules text in the Core Rulebook (Paizo, Chapter 3: Classes) is explicit on this point.
The key distinction: Advanced Alchemy produces items with a 24-hour window; Quick Alchemy produces items that expire in roughly 6 seconds of game time. The Alchemist cannot stockpile Quick Alchemy items between encounters.
Perpetual Infusions, a feature unlocked at 5th level, allows the Alchemist to produce a small set of items — defined by their research field — without spending any reagents at all. The available items are limited to 3rd-level or lower items from a restricted list, and the feature does not scale with reagent batches. It is reliable, not powerful.
Common scenarios
Three situations generate the most rules questions at organized play tables:
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Can an Alchemist craft items for the party during downtime? Yes — using the standard Crafting skill rules from the Core Rulebook (Chapter 4: Skills), not the infused reagent system. Downtime-crafted items are permanent, do not expire, and follow the 4-day minimum crafting period with daily Crafting checks against the item's DC. They are not infused and have no Intelligence modifier dependency.
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Does the Investigator's Alchemical Sciences methodology give full Alchemist access? No. The Investigator (introduced in the Advanced Player's Guide, Paizo Publishing) gains a limited version of the Alchemist's toolkit — specifically Advanced Alchemy and a formula book — but the reagent pool is calculated differently and the class does not gain Quick Alchemy unless the player takes the Alchemical Crafting feat chain separately.
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Can an Alchemist take the Alchemist Dedication multiclass archetype? Yes, but the Core Rulebook multiclass rules require a character to not already be an Alchemist. The Dedication provides a scaled-down reagent pool (level ÷ 2, rounded down) and access to a 4-formula book — meaningfully weaker than the base class, intentionally so.
Decision boundaries
The rules establish clear priority when items or effects conflict:
- Infused items crafted through Advanced Alchemy cannot be sold — the rules text in the Core Rulebook states they are too unstable for commercial transaction and expire too quickly to hold value.
- A non-infused alchemical item crafted during downtime can be sold, traded, or stored indefinitely.
For players building Alchemist characters across different campaign structures, the Pathfinder site index covers the full range of class and system references available. The mechanical logic underlying these subsystems — action economy, resource pools, and crafting timelines — connects to broader design principles explained in how recreation works conceptual overview.