When purchasing aluminum foil, the most critical factors are thickness (measured in microns) and alloy grade. For food packaging, Alloy 8011 is the industry standard due to its high tensile strength, while Alloy 1235 is preferred for flexible packaging and laminations. You must specify the temper (usually O for soft annealed) to ensure the foil is flexible enough for wrapping. Additionally, verify the pinhole rate, as high-quality foil should have near-zero pinholes to provide an absolute barrier against light, oxygen, and moisture.