Variety is the spice of life. Mixing things up is usually a good idea. Would an un-tossed salad with all the veggies in separate little compartments be as enticing? Probably not. Who drinks rum & coke in separate glasses? Mixing things up is good in food and drink. It’s not so good in layered vinyl graphics. Vinyl can be applied in layers on most substrates. But mixing layers of cast, calendared and extruded films can lead to the sign maker’s equivalent of indigestion. Maybe even a hangover. Following some basic guidelines for layering sign vinyl will lead to sweet success. Here’s what you need to know.
Different Kinds of Vinyl
There are different kinds of self-adhesive vinyl films. Most of what we offer at SIGNWarehouse falls into four categories. These are cast and calendared PVC vinyls, metalized films, and reflective sheeting. All of these products have different characteristics based on how they’re manufactured. Cast vinyl is manufactured horizontally on a moving web. Calendared vinyl is made by squeezing a mass of PVC through a series of vertically stacked rollers. Calendared vinyl may be monomeric or polymeric. Monomeric vinyl is generally marketed as an ‘economy’ film. Polymeric vinyls are generally referred to as ‘intermediate calendared’ vinyl. You’ll find a more detailed comparison of cast and calendared vinyl here.
Metalized films such as holographic vinyls and chrome are made by embossing and extruding metallic foils. You’ll find a more complete introduction to holographic vinyl here. For the purposes of this article, we just need to understand that the foil content in the face film affects how they interact with substrates and other self-adhesive films.
Reflective sheeting is made by laminating a layer of acrylic or polyester over glass beads or a prismatic structure. The glass beads or prismatic layer give the film its reflective properties, but the top layer of PET or acrylic gives it different adhesion properties than standard PVC vinyl. Click here for more details on reflective vinyl.
All Vinyl Shrinks
The first thing to understand about successful layering of vinyl is that all vinyl shrinks. This happens over time as it’s exposed to heat and sunlight. Generally speaking, the longer the outdoor durability rating the more slowly the film shrinks in response to the elements. Monomeric calendared vinyl shrinks most quickly, hence its ‘economy’ designation. Metalized films like Schein Chrome and Schein holographics have similar shrink rates and durability ratings depending on the product. Typical life spans in this category range from two to five years. Shrinkage and aging of metalized film is accelerated by exposure to heat because the foil layer retains more heat than a standard PVC face film.
Polymeric or ‘intermediate calendared’ vinyls like EnduraGLOSS and ORACAL 651 have better dimensional stability than monomeric films. These vinyls shrink more slowly and last longer. Reflective sheeting can last up to seven years outdoors. On the top of the chart is cast vinyl, which shrinks very slowly and lasts up to 12 years outdoors. Click here if you’d like to expand your understanding of factors that affect outdoor durability.
What Not to Do
These varying shrinkage characteristics become a problem when different kinds of vinyls are applied together and respond to the elements on different timetables. It’s like listening to a band where the drummer and the rest of the musicians are on a different rhythm. It’s discordant. This is what happens when you apply different kinds of vinyl in layers. Putting a monomeric vinyl on a polymeric vinyl won’t work because the top layer will shrink more quickly than the bottom layer. This stresses the bond between the layers which can lead to tearing and other ghastly problems (Fig 1). Applying calendared film over reflective sheeting or cast vinyl can lead to similar failures. Even layering a 3 mil intermediate calendared vinyl over a 2.5 mil calendared film can result in failure for the same reason. To avoid this kind of installer indigestion, use colors from the same product line whenever possible.
What if your customer insists on a design that requires EnduraGLOSS Cherry Red and Schein Fluorescent Yellow? The best option here is to explain the dangers of applying one vinyl over the other and sell them a design that applies both films directly to the substrate with no overlapping.
Overlaminate film should also be matched with similar kinds of vinyls. Never use a calendared overlaminate on a cast vinyl or an economy calendared overlaminate on a premium calendared vinyl. The two layers must expand and shrink at the same rates otherwise delamination failure can result. For best vehicle wrap results, Use PrismJET 230 Ultra with 231 overlaminate film, ORAJET 3951RA with 290G, and Avery MPI 1105 EZRS with DOL 1060 or 1360 overlaminate.
Variety may be the spice of life, but mixing things up is not a good recipe for layering sign vinyl. Use layers from the same vinyl product line whenever possible. Apply cast on cast, intermediate calendared on intermediate calendared, etc. If your customer insists on mixing it up, apply different kinds of vinyl side by side, but not in layers. And use matching overlaminate film on your digitally printed vinyl graphics and vehicle wraps. It is a proven formula for success.