Why do masking tapes sometimes leave residue?
This is a very common question and there are usually two possible answers depending on the application. Firstly, the wrong tape is being used or secondly, the tape is being removed at too high a temperature when the adhesive is still ‘soft’.
Choosing the wrong tape is a common issue and is usually driven by a lack of knowledge of the construction of a masking tape – specifically the adhesive. With the exception of very high temperature masking tapes, such as for powder coating, a rubber adhesive is used. For general purpose masking tapes, if used indoors and kept out of direct sunlight, a good quality tape will remove cleanly after up to 3 days use, but there are others which will leave residue even after a few hours! As the process temperature increases (driven by the required curing temperature of the paint system) then it becomes even more important to match the masking tape to the application. This is because to provide the necessary temperature resistance, the amount of ‘cross-linking’ (or ‘curing’) of the polymer chains in the adhesive needs to be increased accordingly, and the greater the amount of cross-linking, the ‘harder’ the adhesive and the higher the temperature resistance. In manufacture, a process called ‘electron beam curing’ is used as the amount of cross-linking can be precisely controlled.
However, temperature and UV radiation (sunlight) can also initiate cross-linking, so if a masking tape with a stated temperature resistance of 80˚C is used when the required oven temperature is 140˚C, there is a very great chance further cross-linking will occur and the masking tape will cure onto the surface to which it has been applied.
So next time you’re at a DIY shop at the weekend and need a masking tape for painting windows and can’t decide between the more expensive, UV resistant option, and the cheaper version, think about how much time and frustration you’ll save by picking the recommended one compared to the few extra pounds out of your pocket.