Thursday, June 26, 2014

Film at Eleven

My friend Nik, in a reference to the film Lawrence of Arabia, likes to call Pasadena "The Sun's Anvil." This is an apt description. I've lived in hotter areas around the Southland, but I've never lived in a place where the sun is more merciless. I've discussed at length the damage the sun has done to the south-facing elements of the Farm House exterior, but in the afternoon it's pretty hard on the west face as well. The sun coming through the front dormer windows will fade anything fadeable within its reach in record time.

For this reason, I have planned all along to install clear UV-blocking film to the front dormer windows when I finished them. I forgot this step when I did the north dormer sashes, but I remembered in time to have some on hand for the south sashes. Thus, after I varnished them, I turned my attention to the task of applying the film to the glass.

I approached this task with considerable trepidation, because I've heard reports for years that it is quite a difficult task, and I've seen my share of badly-done installations. Still, I had the film, and I had everything necessary to install it, so I figured I'd give it the old college try.

I unwrapped the package of film and found this:

(Please forgive those green horizontal bands; I forgot to turn off the overhead fluorescents.)

Great. Both the film and the backing were clear. How was I supposed to know which was which? More importantly, how was I supposed to separate one from the other?

Fortunately, the instructions provided the answers to these questions, in the form of a neat trick that's sure to come in handy in the future: simply apply a piece of tape on each side of the film-backing sandwich near a corner, leaving an inch or so trailing off the edge as a handle. Then, use the tape pieces as handles to pull the film and backing apart. The film is the side that has adhesive on the back of it, in case that isn't already apparent.

Before doing this, you have to cut the film to size. The instructions say to add an inch to both dimensions to provide a trim allowance. I did this for the first sash only, just to make sure I had the process down correctly before I did any more cutting.

The next step is to get the glass surface scrupulously clean, so that nothing comes between the film and glass to cause a visible bump or air bubble. After a thorough cleaning with Windex and Invisible Glass, I scraped the entire surface of the glass top-to-bottom and then side-to-side, using as lubrication a water-based surfactant spray that came with the installation kit.

I was surprised to discover how much junk came off of glass that had appeared perfectly clean. As per instructions, once I was done scraping I marshaled the junk and the remaining surfactant into one corner using the supplied squeegee, then removed it all from the glass using a lint-free cloth.

Now, I was ready to apply the film. The basic idea is to wet the glass uniformly with a thin layer of the surfactant in order to keep the adhesive from adhering to the glass while you position the film. Then, remove the backing from the cut piece of film, being extremely careful not to allow the exposed back of the film fold over on itself and get stuck together. 

Then, you place the film adhesive side down on the glass, slide it into position, then use the squeegee to remove the air bubbles and excess surfactant from under the film, starting in the middle and moving towards the edges, sopping up the excess surfactant periodically from the outside of the film.

The idea here is that once this step is done up to the edges, then you trim the excess film along the edges using the supplied trimmer. This trimmer leaves a 1/16" gap between the film and the edge to provide a route for the remaining air and surfactant to exit. Then, you finish the squeegeeing right up to the edges, then allow the film to sit undisturbed until the whole shebang dries.

Everything was going so incredibly well for me as I followed these instructions that I was positively ecstatic, until I got to the trimming part. I ran the trimmer down one edge, and it trimmed effortlessly right up until I got to the corner. It was at this point that I realized that I still had the overlap to cut through, and nothing to cut it against except for my freshly-varnished wood. Oops. The only thing I could do was pull the trimmed edge back up carefully, finish the cut with a pair of scissors, then squeegee it back down. This did not go extremely well, but it went well enough. Here's what I had at this point:

The side on the right of the picture is the one already trimmed.

Okay, I thought. Now I just have to come at this corner down the other side with the trimmer and it will be done. The thing is, I did, but it wasn't. The last eighth of an inch would not get cut, no matter what I did with that stupid trimmer. The film just refused to yield. I finally tossed the trimmer aside and used a utility knife blade, but instead of the film's cutting, it just tore. I probably should have used an X-Acto knife, but that simply did not occur to me in the heat of battle. I did a better job with the remaining corners, and miraculously, the finished sash turned out looking pretty good—if you didn't look too closely at the corners.

Still, it was obvious after that experience that these instructions were not written with this situation in mind. They would have worked with a car window or a modern aluminum-framed sash, but not with a wood sash, nor in fact with any situation where the glass is so deeply recessed on all sides.

Thus, for the remaining sashes I cut the film to as close as possible to the exact size before application. I cut it a bit too small in two of the three sashes, but I did cut all the pieces straight and true, so because the film is clear, you have to know what you're looking for to see the gap. In any event, with the sills back in place the film is as a practical matter invisible.

So, I would say that this job is not really terribly difficult after all, as long as you can take the sills out and put them flat to work on them. Installing them in place would not only be much more difficult, it would also be quite messy. Oh, and one other thing: That surfactant spray is nothing but water with a little detergent in it to lower its surface tension; one could easily make it with a few drops of liquid dish detergent (such as Joy or Dawn) in a quart of distilled water (you don't want any dissolved solids in it) put in a spray bottle. Many people also say that a credit card works just as well as that squeegee, but I think the squeegee provided in the installation kit makes for a faster job, simply because it is bigger and a bit more flexible.

I'll go back and install the film on the north dormer windows when workflow allows, but I'll have Wifey measure and cut the film. Because of her considerable skill at sewing, she can cut any pattern perfectly.

* * *

My faithful assistant, always there to lend a paw.


  1. Yeah, I am always pretty -- pardon the expression -- torn when doing this kind of work. About the only thing I find that almost kinda sorta reliably works is just starting with a brand new blade and hoping for the best.

    1. That's the problem with the trimmer I was using: the blade is irreplaceable, and obviously had given up the ghost pretty quickly. I did use a fresh utility blade, but it wasn't really the proper tool to be using at that point. Next time I'll know better, unless I forget.

  2. Film at eleven, I get it! Hopefully there is clear sailing ahead.

    1. Coming up with a snappy title is often the hardest part of writing this blog. If I can think of one that is both relevant and contains a pun, it goes right up at the top without further ado, no matter how corny it may be.

      Okay, actually, the corn is a feature, not a bug.

  3. UV blocking film is a grand idea. It looks totally invisible from the picture and worth all the extra work.


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