ShelfYears

Does lacquer go bad?

Sherwin-Williams gives a straight lacquer 24 months unopened — but if it is a pre-catalyzed lacquer, the catalyst is already at work in the can and the window drops to 6 months from the day it was catalyzed.

Updated

Lacquer
Sealed
2 years
Opened
6 months if catalyzed
SOLVENT LOSS & ACID CATALYSIS
Degraded performance

Sealed: 2 years Tier 1

Sherwin-Williams lists package life for Sher-Wood CAB-Acrylic Lacquer as 24 months, unopened. Its catalyzed (pre-cat) lacquer sheet gives the same 2 years unopened, then adds the number that actually governs a pre-cat can: 6 months once catalyzed. Two years is the figure for the can on the shelf; six months is the figure for the can someone already added catalyst to.

By manufacturer — the disagreement is information
Brand Sealed window
Sherwin-Williams (Sher-Wood CAB-Acrylic Lacquer) 24 months, unopened
Sherwin-Williams (Sher-Wood Catalyzed Lacquer, pre-cat) 2 years unopened, 6 months once catalyzed

After opening: 6 months if catalyzed Tier 1

For a straight lacquer, opening the can mostly costs solvent: the thinner flashes off, the material thickens, and it stops atomizing properly. For a pre-catalyzed lacquer the clock is chemical and it does not stop. Sherwin-Williams is explicit — the catalyst causes a chemical reaction in the package and dissipates after 6 months, and performance properties are downgraded. Adding more catalyst does not restore film properties.

How to tell it's gone off

  • Lacquer that has thickened and strings off the stir stick instead of running off it.
  • A hard ring of set resin around the inside of the rim where solvent escaped.
  • Cloudiness or a milky cast in a finish that should be water-white.
  • Sediment or seeds that do not stir back into the material.
  • A pre-catalyzed can more than 6 months past the date it was catalyzed, however good it looks.

If you use it anyway

Degraded performance

Lacquer that has gone off sprays badly and dries soft. A thickened can goes on orange-peeled and cloudy; a stale pre-cat lays down a film that stays softer than it should and marks under a fingernail long after it ought to be hard. Both faults come back off with lacquer thinner and another coat, so what it costs is the re-spray.

Why it goes off — SOLVENT LOSS & ACID CATALYSIS

A straight lacquer is resin dissolved in solvent, and it dries by the solvent leaving — which means the only thing that ages it in a sealed can is solvent finding a way out. A pre-catalyzed lacquer is different in kind: an acid catalyst has been stirred into it to cross-link the film, and that acid does not wait politely for you to spray. It works inside the container, spending itself over about six months, so a pre-cat can that sat too long dries to a softer, weaker film than the label promises — and Sherwin-Williams says more catalyst will not bring it back.

Every page here commits to one of four states — Harmless · Degraded performance · Equipment damage · Safety issue. How the verdicts work.

How to store it

Sherwin-Williams' storage line for a catalyzed can is the one worth copying: store at room temperature, under 80°F, after catalyzation — higher temperatures will reduce the storage life. Keep the can tightly closed so the solvent stays in it, and keep a catalyzed can labeled with the date it was catalyzed, because that date, not the purchase date, is the one that counts.

Never store lacquer near heat, sparks or an open flame — Sherwin-Williams lists its flash point at 37°F.

Sources