The backing material (or liner) for a label is usually coated with a silicon layer on the upper side (closest to the label stock adhesive) to allow the face stock to release from the backing as it is applied to the end product.
The backing material choice may matter depending on whether you require clarity or visibility through the backing (such as when overprinting) or the strength needed for particular types of machine applicators.
Backing materials come in 3 main types: Glassine, Kraft or Filmic.
- General purpose uncoated transparent backing paper.
- Comes in a range of colour and weight variations (though usually white, yellow or a faint blue).
- Used for labels being overprinted as sensors can detect gaps between labels.
- Coated on one side and used when extra stiffness is required.
- Comes in a variety of weights and colours (white and brown).
- Used for sheeted or A4 laser labels as it maintains good rigidity when fed through laser and ink-jet printers and copiers.
- Comes in either clear polyester (PET) or polypropylene (PP).
- Used when the backing needs to be clear and very strong for high speed applicators.