Material Identification and Composition
Aluminum foil is produced from aluminium or an aluminium alloy, most commonly the 1xxx and 8xxx series for packaging grades, and appears silvery-white with a bright, hard surface. Tin foil was historically produced from metallic tin and has a faintly bluish-white cast with a much softer, more ductile feel. The household product sold today as tin foil is almost always aluminium foil sold under an inherited name; true tin foil is now a niche material.
Packaging foil is ordered to ASTM B479/B479M, which covers general requirements for aluminum and aluminum alloy foil. Unsupported household gauges begin around 0.0005 in (about 12.7 micrometres), a thickness that keeps the sheet flexible while remaining an effective barrier.
Physical and Thermal Properties
| Property | Aluminum foil | Tin foil |
|---|---|---|
| Melting point | about 660 degrees C | about 232 degrees C |
| Density | about 2.70 g/cm3 | about 7.31 g/cm3 |
| Thermal conductivity | about 235 W/(m.K) | about 67 W/(m.K) |
| Hardness and ductility | Harder, holds a fold | Softer, stretches easily |
| Surface colour | Bright silver-white | Dull bluish-white |
The difference in melting point is the one that decides most practical cases. Aluminum foil survives oven and grill temperatures; tin foil cannot, and it becomes brittle and loses its shape well below the point at which it melts.
Barrier and Chemical Behaviour
Both metals are effectively impermeable to moisture, oxygen and light at foil gauges, so the difference is chemical rather than barrier-related. Aluminum forms a thin, self-healing oxide layer that keeps it stable in air and neutral water, but the metal is attacked by strong acids and by alkaline or strongly salty foods left in prolonged contact, which is why bare foil is not used as a long-term container for such fillings. Tin is comparatively inert to many foodstuffs and to mild acids, but its low strength and high density make a foil of practical thickness expensive and heavy.
Practical Performance and Typical Uses
Aluminum foil is chosen for baking, grilling, freezing, roasting trays, lidding and high-speed wrapping, and for laminates where a paper or film layer supplies the strength. Tin foil survives in specialist work such as decoration, some electrical applications and historical restoration, where softness and tarnish resistance matter more than strength or cost per square metre.
When a specification calls for a foil, the useful questions are the maximum service temperature, whether the contact is acidic or salty, and the required stiffness during wrapping. The answer to those three questions usually identifies the material without ambiguity.
Frequently Asked Questions
Q: Is household tin foil actually tin?
A: No. Almost all foil sold today is aluminum foil; tin foil is a niche product kept for specialist uses.
Q: What is the melting point of each material?
A: Aluminum melts at about 660 degrees C and tin at about 232 degrees C, which is why only aluminum foil is used for oven and grill work.
Q: Which material conducts heat better?
A: Aluminum, at roughly 235 W/(m.K) against about 67 W/(m.K) for tin, so aluminum both heats and cools faster.
Q: Can aluminum foil be used with acidic food?
A: Only for short contact; prolonged contact with acidic, alkaline or strongly salty fillings attacks the metal, so a lined container is used instead.
Q: Why does aluminum foil feel stiffer?
A: Its higher strength and stiffness per unit thickness let a thin gauge hold a fold, while tin stretches and deforms instead.
Q: Which standard applies to packaging foil?
A: ASTM B479/B479M, which sets general requirements for aluminum and aluminum alloy foil.