# Sealant shelf life after opening: what still works

> Unopened shelf life is printed on the cartridge; opened is the number nobody prints. How long PU sealant lasts after opening, and how to tell it has gone.

Updated: 2026-11-12 · Source: https://karmindadhesive.com/resources/sealant-shelf-life-after-opening/

Every cartridge prints an unopened shelf life. None prints what happens after the cap comes off, which is the number a workshop actually needs: the cartridge that was opened for one windscreen and sits on the shelf for a month, the sausage left in the gun overnight, the bottle of PUR that has been in the van since spring.

## What the printed figure covers

A six-month shelf life means six months in the unopened container, stored between roughly 5 °C and 25 °C, away from direct sun. It says nothing about a cartridge that has been opened, half-used, and re-capped with a blob of cured sealant in the nozzle.

The clock after opening is set by moisture. One-component PU cures by reacting with water in the air; every time the cartridge is open, the surface meets moisture and starts to skin.

## What happens after opening, by product

| Product | After opening | Why |
|---|---|---|
| PU cartridge (310 ml) | 2–4 weeks with a clean nozzle and tight cap | Skin forms in the nozzle first; the body stays workable while the cap seals |
| PU sausage (400/600 ml) | Same day; do not return to the foil | The film is opened at the nose and cannot be resealed against air |
| PUR wood adhesive (bottle) | 4–8 weeks if the nozzle stays dry | Moisture cures the glue line; a wet nozzle cures the bottle |
| Activator or primer (can) | Up to the printed date if closed properly | Solvent loss, not cure, is the failure mode |
| Two-component product | Pot life after mixing, not shelf life | Once mixed, the clock is minutes to hours |

## Heat, cold and the container

- **Heat** accelerates skinning and can gel a cartridge. A container that crossed an equator in August is a different risk from one that went from factory to warehouse.
- **Cold** slows the cure but does not reset it; frozen-and-thawed PU can separate. Let a cold cartridge reach room temperature before use rather than warming it on a heater.
- **Sun** on a pallet raises the temperature far above air temperature. Store cartridges in the shade, not against a south-facing wall.

## How to tell a cartridge has gone

1. **Skin in the nozzle** — normal; remove it and purge.
2. **Lumps or grit in the bead** — cured particles from the nozzle or the cap; the cartridge is contaminated.
3. **Stringy, short bead** — the product has thickened; it will not tool or wet the joint.
4. **Skin-over in minutes on a coupon** — the cartridge is older than its working life.
5. **Tacky after the full cure time** — the balance of the system has moved; do not use it in a joint that matters.

## What to do with old stock

Test it, do not guess. Run a bead on an offcut of the actual substrate, cure it at site temperature for the full cure time, and pull it. A bead that tears at the interface, or stays soft in the core, is finished — use it for a non-critical mock-up or discard it.

For a visible or structural joint, the calculation is simple: a cartridge costs less than the labour to redo the joint, and far less than the claim that follows a failed one.

## What this means for buyers

Order against the production date, not the delivery date. Ask for the batch number on the carton and the date of manufacture; a supplier who cannot state either is selling you an unknown number of months. For a project with a long installation programme, stage deliveries instead of holding six months of stock in a warm container.

## Evidence note

The ranges here are manufacturer and workshop practice, not measured curves. The only evidence for a specific cartridge is the cure test on your substrate; treat the two-to-four-week figure as planning, not as a guarantee.