Vinyl film is usually cast or calendered. Deciding which to use is simple once the terms are understood. The definition of calendered is having a surface made smooth and glossy especially by pressing between rollers. Cast on the other hand means to form into a particular shape by pouring it in a fluid state and letting it harden.
A calendered intermediate film is generally an 80 micron thick film. The thickness refers to the film itself and does not include the adhesive that is applied. Depending on the adhesive used it will add another 25 to 50 microns to the thickness. During the manufacturing process the raw materials such as resin, plasticizers, stabilizers, and color pigments are combined and heated. This semi-solid vinyl material is then feed into a calendaring machine, which contains a series of rollers. The first set of rollers produces a rough gauge. The following set of rollers determines the gloss level and final thickness. The film is manufactured in a continuous web process, where it is subjected to continuous stress, pressure, and heat. The film is actually stretched and pressured into its final form.
Because of the manufacturing process the film is susceptible to extreme heat and cold, and tends to shrink back to its original size. Cracking, peeling, and adhesive ooze can be problems. The material is also produced in large batches, which limits the number of colors that are available.
Cast film is made in 50 micron thickness. It is thinner than calendered film and is easier to mold over irregular surfaces and small letters and designs are easier to weed. The raw materials are of better quality and a different manufacturing process is used. After the raw materials are mixed, the film is made by flowing liquid at a controlled thickness and allowing it to harden. The material is not stressed nor stretched and no pressure is applied. The vinyl material is transferred through rollers to a casting paper. Material stress is minimal because the liquid vinyl is supported by the casing paper once it leaves the rollers. This makes the material suitable for outdoor use and long exposure to extreme heat and cold. Shrinkage, cracking, and splitting are less of a problem than with calendered films. Casting machines are much small than the large calendaring machines hence shorter production runs are possible and a wider variety of colors are available.
We now know that cast film is more expensive than calendered film do to manufacturing processes and that each film has its own characteristics. Generally speaking if a film is to be used indoors the less expensive calendered may do the job for you. If the signage is to be used outdoor or the inside of exterior glass then cast is a better choice.
A cast film resists bubbling, fading, and peeling due to long term exposure to the sun’s ultraviolet rays. Eventually the rays will cause deterioration of both the vinyl and the adhesive. If you are applying the film to uneven surfaces a cast film is the best because it has a longer life expectancy when exposed to harsh weather conditions. Cast film with appropriate adhesive will stick longer, better, and faster than an adhesive on a calandered film. The adhesives applied to calendered film are more susceptible to moisture, solvents, and sunlight and may cause signage to turn yellow or curl with time.
Always choose the film that best fits the requirements of the job. In general cast for outdoors and calendered for indoors. If you don’t know where the graphics will be used, be safe and use a cast vinyl.
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