Aluminium Foil Temper Grades Explained: O, H14, H16, H18, H22 and H24
Temper decides whether your foil folds, wraps or springs back. Here is what each designation actually means on the rolling line, and how to pick the right one.
Temper is the one specification buyers most often get wrong. Two rolls can have identical alloy and thickness and still behave completely differently on your converting line, because temper describes how much the metal has been work hardened after annealing.
What the designation means
The letter tells you the condition, the number tells you how hard it is. O is fully annealed, the softest and most ductile state. H means strain hardened, and the two digits that follow describe the amount of cold work and any partial anneal applied afterwards.
- O — fully soft. Wraps around fingers, dead-folds without springing back. Standard for household, food service and laminating foil.
- H14 / H16 — quarter and three-quarter hard. Moderate strength with some formability left. Common for fin stock and light forming.
- H18 — full hard. Maximum strength from rolling alone, minimal elongation. Used where stiffness matters more than formability.
- H22 / H24 — strain hardened then partially annealed. Similar strength to H14 and H18 respectively, but with better ductility, which is why they are preferred where the foil must form without cracking.
Why H24 is often the better choice than H18
If a specification calls for H18 but the part has to be drawn or bent, the foil may tear at the bend. H24 reaches a comparable strength while retaining enough elongation to survive forming. If your press is rejecting material, the temper is the first thing to review, before you blame thickness or alloy.
What we control on the line
Temper is set by the amount of cold reduction and the annealing cycle, and verified by tensile strength and elongation testing per batch. Test certificates are issued with each shipment so your engineers can confirm the material matches the specification before it reaches the press.
We supply O, H14, H16, H18, H22 and H24 across our aluminium foil roll range, and fin stock tempers for heat exchanger fins. If you are unsure which temper suits your process, send us a sample of what you run today and we will match it.