Glue cure time calculator
"When can I unclamp?" depends on the glue, the temperature, and the humidity. The bottle says 30 minutes; in a 55°F shop that's a lie. This calculator adjusts three cure milestones (open time, clamp time, full cure) for your actual shop conditions.
Calculator
The three numbers and what they mean
Open time is the working window: the glue is wet enough to transfer and assemble. PVA at room temp is ~5–10 min; polyurethane is even shorter; hot hide glue can be a few seconds.
Clamp time is when the glue has enough green strength to hold under no load. You can take the clamps off and the joint will hold its shape — but it isn't fully cured.
Full cure is when the glue reaches design strength (typically 80–100% of its ultimate value). Planing, scraping or stressing the joint before full cure can crack the partially-cured adhesive.
Why cold slows everything
Glue cures through a chemical reaction (PVA: water loss; poly: moisture-driven; epoxy: cross-linking). All of these slow down in the cold. The rule of thumb: cure time roughly doubles for every 10°C (18°F) drop below 70°F. At 50°F, you're looking at 2–4× the bottle's stated clamp time.
Limitations
- Open / clamp / cure times are typical values. Always test with your specific bottle — manufacturers vary.
- Doesn't model joint gap. A loose joint (no clamp pressure) takes much longer to reach strength, regardless of glue.
- Doesn't predict glue-line failure under shock load — that's a different (worse) test.
- Epoxy "5-minute" is a set time, not full cure — most epoxies take 24 hours to reach design strength.
Frequently asked questions
Can I speed up cure with a heat gun?
For epoxy, yes — most epoxies cure faster with mild heat (up to ~100°F). For PVA, the cure is water loss, not heat-driven; a heat gun mostly dries the surface before the water has migrated out, leaving a weak joint. Use a space heater and time, not a heat gun.
Is Titebond III actually waterproof?
Yes — Type III PVA passes ANSI/HPVA HP-1 for water resistance. It's not marine-grade for immersed use, but it's fine for outdoor furniture, cutting boards (with a food-safe finish) and kitchen items that get wet occasionally.
Why does my glue joint keep failing?
Three usual suspects: (1) wood too dry (<6% MC) sucks the water out of PVA before it can cure. (2) insufficient clamp pressure — the joint was starving. (3) glue starved — too little glue spread. Check your process, not the glue brand.