Which Primer For Architectural Film Substrates (Part II)

Architectural film guru, Brent Williams, talks us through some of the common mistakes people make when selecting the correct primer for projects.


Last month we went into an introduction to primers and how choosing the right one is crucial to the success of a project. This month we’re going into detail on each primer and how to determine which one will work best for you based on the surfaces you’re going to be wrapping. 


To make this as simple as possible, I’ll break it down to the major points. These are very broad strokes, so reach out if you need me to really get into the works. 


First, the surface needs to meet the expectation of the client. If the finish is supposed to be “stainless steel”, you MUST be able to get the surface to the finish state of the final material. In this case, if the substrate is rough-hewn oak, you’re just not going to be able to install a stainless finish on it…it’s never going to be smooth as a metal, so this will be a situation where you should suggest a change of finish to something that complies with the existing conditions more efficiently. Sure, you can do things like apply a high-pressure laminate over that oak to make it slick enough to apply the stainless, but now you’ve introduced significant additional cost to the project and may make the use of the architectural film moot, simply because of cost. 


Next, ascertain the porosity of the substrate. Simply stated, is it hard and non-porous, or is it softer and porous? Things like metal, glass and plastics are completely non-porous. In these cases, you will use solvent-based primers like Primer 94 in most situations, because of its quick drying properties. With these primers, you are able to apply them quickly and efficiently. On the other end of the spectrum, there are the porous substrates, like gypsum, unfinished wood, wall coverings and other surfaces that are able to absorb and hold liquids. Our solvent-based primers don’t work at all with these types of surfaces, because they flow into the porous surface and are effectively “gone” with regard to being able to assist with helping the material adhere to the surface. Instead, you need a more robust priming solution for these surfaces that take into account porous surface conditions. 


Primers like 3M’s PW-2000 Water-Based Primer are able to bridge the pores on these kinds of surfaces and provide the necessary bond strength required for the project. As a side note, the PW-2000 is a product specifically engineered for these architectural film adhesives… and Primer 94 is not. That primer was created specifically for 3M’s VHB Tapes series but was later discovered to be very powerful as a primer for architectural film adhesives. But that primer isn’t as strong in overall bond strength as the PW is. 


In between the “hard” and the “soft” non-porous categories are some oddballs that are a little bit of both. Materials like MDF and PVC Board will have hard, non-porous surfaces, but the cut edges have porous cellular structures. In these cases, you will need to possibly either use both types of primers or do something to further prepare these surfaces. In the case of PVC Boards, you can lightly sand the edges to remove the ragged, open cellular structure, rendering that surface smooth and non-porous…and ready for Primer 94. If you do NOT sand that surface, you can apply a water-based primer to those porous surfaces but use a solvent-based primer on the hard faces. 


In the case of MDF, even sanding does not get the required surface hardness…the solvent-based primers simply soak in and are effectively “gone” providing zero quality bond strength. On very porous surfaces like gypsum, these water-based primers are a godsend, as they have a very high bond strength on these kinds of surfaces. When applying these primers, you are going to apply the primer to 100% of the surface, as the gypsum surface is never going to be directly compatible with the architectural film finishes. In some cases where a very high bond is required, you may need 2 or even 3 coats of the water-based primer to be sure that you have the bond strength that you require. 


Similarly, there are certain situations where you need advanced holding power, things like undulating surfaces or compound curves. In these situations, you may need an additional adhesive. In thermoformed applications, you are “stretching” the material…making it larger than it originally was. This also means that the “X amount” of adhesive per square inch is a lower ratio. You have spread a fixed amount of adhesive over a larger area, therefore lowering its adhesive strength. In those cases, you will be adding a proper adhesive over an equally properly prepared and primed surface. In these cases, you will need to experiment in advance on how these surfaces and primers interact to assure that you have the proper amount of adhesion requisite to the needs of the project and the requirements of the design professional on the project. 


Next month we’ll dive a little more into the architectural film-related geekdom, with a look at how these finishes are built and the properties of the materials and adhesives that make each of these different surface finishes distinctly different from one another. That’s why I’m here, effecting to help the entire architectural film industry move forward. I’ve learned, frequently through paying some “stupid tax”, how these materials work, how it is applied, specifically how to prepare surfaces and how to manage application projects to help you ensure total success. Onward and upward!


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