[00:00.00]W1: I know you’re all excited about our class project.[00:04.00] But before we get started on the design of our mural, let’s review some of the technical requirements for murals. [00:10.66]What factors do we need to keep in mind? Yes, Lydia?
[00:15.36]W2: The mural has to be permanent. [00:17.06]It has to last as long as the building. [00:19.26]And it has to be sturdy enough to put up with conditions like the walls being washed.
[00:23.16]W1: Good points. Yes, David?
[00:25.16]M: It should have a flat finish so you can look at it from all angles without seeing any glare.[00:29.86] And the design should be laid out so you can see it while you’re walking rather than standing still.
[00:34.66]W1: Yes, those are all things we need to bear in mind. [00:37.96]We want people to take in our mural—all of it—from a moving position, since they’ll be observing it as they walk through the lobby to the elevators. [00:47.06]And let’s not forget that our mural is more than just a large-scale work of art done on a wall instead of a canvas. [00:54.46]The term “mural” implies a distinct feeling or nature, a quality that’s appropriate to the architecture and the function of the room. [01:03.46]A mural is an integral part of the building. [01:06.66]If it’s painted in an existing building, like ours will be, it should be planned to fit into the architectural design, instead of giving the impression that it’s a surface decoration. [01:18.46]Now, what are some of the technical requirements for our wall?
[01:22.36]M: Obviously, the wall shouldn’t move.[01:24.66] It shouldn’t shrink or settle because that could cause cracks in the paint or plaster.
[01:29.36]W1: Yes, it’s vital that our wall be perfectly immovable. [01:33.26]And for murals like ours—remember, our mural will be on the interior side of an exterior wall—another important requirement is that dampness should be excluded. [01:44.66]Dampness can result from water seeping through porous materials or through joints, corners, or flaws in the building construction. [01:53.46]When water leaks through a wall, it may dissolve the salts that are in the building materials. [01:59.06]When the moisture dries, the salts are deposited in the form of white, moldy-looking film on the surface of the plaster.[02:07.26]This greatly weakens the plaster, which can crumble or crack, and, of course, it’s disastrous to the mural.
[02:14.66]W2: Can moisture make the paint peel off?[02:16.66]W1: Yes, it can. When moisture penetrates a wall coated with paint, it causes the plaster to expand and the paint to peel off—either in small flakes or in big pieces. [02:28.16]And we don’t want that happening to our , work, so we’ll need to take measures to prevent it.[02:33.46] Our goal will be to reduce expansion of the plaster and to lessen the condensation of moisture on the surface.[02:40.86]So our first rule is to exclude dampness as much as possible.
[02:46.26]M: Don’t we also need to guard the plaster from extreme changes in temperature?
[02:50.16]W1: Yes. So, how are we going to do this?
[02:52.86]M: We could create an air space between the outer wall of the building and the plaster.[02:57.86]We could do this by building a screen or, um, like a false wall just inside the exterior wall, and then we put the plaster for the mural on this false wall. [03:08.46]There’d be like an inch of air space between the false wall and the exterior wall. [03:13.06]The air space would have an insulating effect. [03:15.86]What I mean is, it would slow down any temperature changes on the plaster.
[03:20.46]W1: Yes, you’re correct about the insulating effect of an air space.[03:25.46]Now, to do this—it’s called “furring” the wall—what we do is, we attach thin strips of wood to the exterior wall, and then we build another wall on top of this. [03:36.56]The furring of the wall creates an air space of one-half to one inch between the outer and inner walls.[03:44.16] That’s enough to protect our mural from moisture and temperature changes, as well as the mechanical strains and stresses of the wall itself.
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