I'm spraying a two-component polyurethane on some metal doors.

Pot Life (Working Time): The window after mixing Part A & B where viscosity stays low enough to spray properly. Once exceeded, the mix cross-links in the pot—viscosity spikes, film build drops, and you risk dry spray or clogged tips. Rule: Mix only what you’ll shoot within this time (usually 2–4 hrs at 70 °F). Hot weather cuts it drastically.

Induction Time (Sweat-in Time): Mandatory wait after mixing before spraying (typically 15–30 min). Allows the chemical reaction to initiate and solvents to equilibrate. Skipping it causes:

• Poor flow/leveling (orange peel)
• Solvent pop/blisters
• Inconsistent gloss/cure

Day-to-Day Impact:

1. Batch size: Calculate sq. ft. per mixed gallon. Mix ≤ 75 % of pot life capacity.
2. Sequence: Mix → start induction timer → prep next door/tape off → spray.
3. Cleanup: Flush gun before pot life ends. Cured poly in lines = new hose/whip.
4. Recoat window: TDS lists min/max recoat times tied to the same chemistry. Miss the max, you must sand.

Pro tip: Keep mixed pail in shade/cool bucket. Use a viscosity cup (Zahn #2) to verify sprayability if pushing time limits.

Ref: SSPC-PA 1, ASTM D1640; always defer to manufacturer’s TDS for exact times at your substrate temp.

Pot life is the time (usually in minutes) after mixing the two components (resin + hardener) during which the coating remains usable — you can still apply it without significant viscosity increase or curing. Once pot life expires, the material begins to gel or cure in the container, making it unusable and potentially damaging your spray equipment.

Induction time (also called “sweat-in time”) is the required waiting period after mixing before application — typically 5–30 minutes — to allow the chemical reaction to stabilize and ensure proper crosslinking, adhesion, and performance. Skipping induction can lead to poor film formation, bubbles, or reduced durability.

How they affect your day:

• Mix only what you can apply within the pot life (e.g., if pot life is 20 min, mix batches no larger than you can spray in 15–18 min).
• After mixing, wait the full induction time before spraying — don’t rush it.
• Monitor ambient temperature: higher temps shorten both pot life and induction time; lower temps lengthen them.
• Always check the TDS for exact values — they vary by product and conditions.
• Never try to “rehydrate” or thin expired material — it’s ruined and can ruin your finish or gear.

Safety note: Two-component polyurethanes often contain isocyanates — use proper respiratory protection (supplied-air respirator recommended), gloves, and ventilation. If unsure about mixing, application, or PPE, consult a licensed industrial coatings professional. OSHA 1910.134 and ANSI Z87.1 apply.