1. Preparations 90% of the battle. Sticking a label onto a poorly prepared surface is like trying to paint a dirty gutter—neither the label nor the paint is going to stay stuck for very long. Remember how important all the scrapping was when you repainted your house! Similarly, we recommend using a cleaning solution and a Scotchbrite® pad. Remove oils. Rough up the surface slightly. Abrading the surface will allow a label to stick even to a transformer having Teflon flow agents in the paint. Also, consider using a premask. This is a very easy and inexpensive step that ensures that you can apply the label without bubbles. The premask allows you to put a great deal of pressure on the label with a hard squeegee and still not mar the surface. The premask is removed once the label has been applied.

2. Beware of the heat. Heat is the primary cause of label failure. The surface of a transformer can reach a temperature of 50°F above the air temperature. This means that labels must be designed to withstand temperatures of 160°F. The effects of heat on a label are cumulative. The films and adhesives must be able to withstand constant cycling of hot and cold. The adhesive must remain pliable and prevent transferring the expansion of hot and cold. The adhesive must remain pliable and prevent transferring the expansion resulting from the heat to the film. If not, the film will prematurely crack and deteriorate.

3. Have a little patience. Adhesives take 72 hours for final cure. A label that can be removed cleanly after 30 minutes can become virtually impossible to remove after 24 hours. Heating the transformer accelerates the cure time.
Most of the films that we recommend have a heavy coat of adhesive. The minimum thickness of the adhesive is 1 mil. We often see labels having only a 0.9 mil thick coatweight. This is called “shaving” and, although less expensive, it also means that the adhesive will not flow out as well. The label’s contact with the underlying surface is not maximized. Thicker adhesives (1.3 to 3 mils) mean that there is maximum adhesive contact with the irregular surfaces common to most transformers.

 
Another important issue is the dyne level of the application surface. Metal has a very high dyne level (700 dynes/cm) and most adhesives stick well to it. Unfortunately, paints commonly found on transformers do not have as high a dyne level. Note that the label is sticking to the paint and not to the metal! Certain polyolefins (such as polypropylene or polyethylene) have a very low surface energy (20-30 dynes) and they require a much softer adhesive. The softer adhesives will stick well, yet give you a much lower ultimate shear strength. Teflon is another plastic with a low surface energy (18 dynes) and, understandably, it is difficult to develop an adhesive to stick to it.