Frequently Asked Questions
What Is A Self-Adhesive Label?
As the term implies, this is a label coated with an adhesive which is self-sticking (or pressure sensitive). Unlike a label that won’t stick by itself, i.e. a label to which moisture (gummed paper), heat (heatseal) or glue (plain paper) has to be applied, a self-adhesive label is pre-coated with an adhesive which is protected by a backing material or liner. When this backing paper is removed, the label will stick to a surface against which the adhesive side is placed. The adhesive does not need to be activated by moisture or heat. It merely requires a small amount of pressure to cause adhesion – it is pressure sensitive! The basic construction of a pressure sensitive label consists of five layers:-
- The face material, on which information and/or decoration is printed
- The primer, or anchor coat, which improves anchorage of the adhesive to the face paper. The primer also acts as a barrier to migration of chemicals that could stain the label face paper
- The adhesive which allows the label to be affixed to a surface
- The silicone coating which allows for easy release of the label from the backing paper
- The backing paper
What is the surface to be labelled?
Is the label to stick permanently, or is removable adhesive required?
Is the label required to stick permanently under ‘deep freeze’ conditions?
To avoid problems it is important that both the printer and the end-user is aware of the importance of these questions. Within reason, self-adhesive laminates can be produced for almost any labelling requirement but the manufacturer cannot be held responsible if the application is incorrect. The GOLDEN RULE is to TEST FIRST. It must be up to the end-user to make sure he has the right label (with the right adhesive) for the job. It is recommended that the following simple TEST FOR ADHESION is carried out before ordering:-
- Apply several sample labels to the surface of the product
- Leave for a minimum of 24 hours
- Lift up one corner of the label and peel slowly away. Good adhesion is indicated by a clearly noticeable fibre tear
- Removable labels can be tested in the same way but there will be no fibre tear and the surface of the product must not be damaged
There are a number of surfaces to which SATISFACTORY ADHESION IS DIFFICULT.
The ones most likely to be encountered are:-
- Low energy surfaces such as those that are silicone treated or contaminated, chemically treated for corrosion resistance, waxed or greasy, or printed polyethylene
- Rough surfaces where surface contact is likely to be low such as wood, metal, lacquered finishes, cork, foam, open weave fabrics, embossed finishes and unglazed pottery
- Moist or cold surfaces such as those caused by condensation, ice or deep freezing
- Irregular shaped surfaces such as glass phials, ampoules or spirit miniatures where the label is applied to a convex surface of less than 25mm diameter
- Dusty surfaces such as plaster, asbestos and fibreglass
- Surfaces which may be extensively exposed to the atmosphere (resulting in eventual failure of the adhesive) such as steel drums.
There are also a number of SURFACES WHICH CAN BE DAMAGED by the application of self-adhesive labels. The more usual ones are:-
- Plasticised plastics such as P.V.C.
- Weak bonded surface finishes such as flock coated fabrics and acrylic vehicle paint
- Animal skins and natural fibres such as suede, leather and wool
- Metal surfaces such as copper, brass and silver
- Some glass surfaces such as optical lenses