Skylighter occasionally stocks pre-framed, round screens which are imported.
They also sell un-framed, square sections of stainless-steel screen, 11.75-inches square, in the 10, 20, 40, 60, and 100-mesh sizes.
Larger mesh sizes are available from various online sources. These stainless steel screens are not inexpensive, but being stainless steel, they can last a long time, especially if they are secured into a well-built wood frame.
Here’s how I would frame a 20-mesh, 11.75-inch square screen.
I want to end up with a wood frame, which is 1/2-inch smaller than the unframed screen in both directions. Having the screen overlap the sides of the frame helps when it comes to stretching the screen tight.
I like to make the wood frame 3.5-inches deep so that plenty of chemical can drop through the screen and accumulate on the paper as I’m using the screen, without piling up and clogging the mesh.
For that reason, I use 1×4 lumber, which actually measures 3/4-inch by 3.5-inches.
I prefer poplar wood, which is readily available from stores like Home Depot. Poplar doesn’t have much grain, so it doesn’t warp much. Although it is classified as a hardwood, it is soft enough for my nails and staples to be easily driven into the wood. Certainly other woods like fir, pine, oak or maple could be used, but I’d be afraid that my staples wouldn’t drive well into the harder woods like the oak or maple.
I showed how I cut paper tubes with a hand miter box and saw in Fireworks Tips #107. If you don’t have a power saw, this same setup can be used to cut the lumber in this project.
I cut four pieces of the 1×4, 10.5-inches long. This will result in a frame with 11.25-inch outside dimensions, which is 1/2-inch smaller than my screen.
At the same time I cut four, 11.25-inch-long pieces of 3/4-inch wide, pine half-round trim, also from Home Depot. These wood strips will form the trim, which will cover the edges of the screen once it is installed on the 1×4 frame.
I use some sandpaper to smooth the corners, edges, and ends of my wood. Then I apply two coats of fast-drying, spray polyurethane to all the surfaces of the wood before assembly. This finish will prevent the wood from soaking up water or chemicals over the years of use and cleaning that the screen will get.
After the polyurethane coats are dry, the 1×4 frame is glued and nailed together. I like to use 6d (2-inch) galvanized finish nails, and polyurethane construction adhesive when assembling the frame.
I pre-drill the nail holes with a 1/16-inch drill bit to prevent the wood from splitting when the nails are driven in. Then I put a thin line of the glue onto the joint, after which I install 3 nails in the joint.
Once the frame has been glued and nailed, I make sure it will sit flat on my workbench. I also check the two, diagonal, corner-to-corner measurements to make sure they are the same, which proves the frame is square. I make any adjustments necessary to ensure the frame is flat and square.
Time to install the screen: I use 1/4-inch long, galvanized staples, and a staple gun to attach the screen to the frame.
I first staple one of the sides onto the frame, with the screen in about 1/16-inch from the edge of the wood on two of the sides. I don’t want any wire sticking out from the sides of the framed screen once it’s done. Such wires could stick and cut my hands while I’m using the screen.
While I’m stapling this first side of the screen, I’m pulling it taut to make sure the side is stretched and straight as it is attached to the frame.
Then, as I make sure the screen is lying flat and that the second side is pulled square, tight and straight, I staple that second side to the frame. After each side is stapled, I hammer all the staples flush into the wood.
Now, I stretch the fourth, unsecured corner, out in the diagonal direction. This can be facilitated by inserting a sharp awl through the screen, and down into the wood. Then the awl can be “cranked” outward, stretching the screen in the process. This works best in the coarser-mesh screens. One has to be careful not to tear the screen when doing this with fine-mesh screens.
I staple the fourth screen corner while stretching it out tightly, and then I staple the third and fourth sides. As I staple those sides, I pull the screen outwards, holding onto the extra 1/2 inch of screen, and pushing the wood inward with my finger as I do so.
This slight inward bow of the wood will hold the screen tight once it’s stapled. Having that 1/2 inch of screen to pull on, is why I made the wood frame 1/2 inch smaller than the screen in both directions in the first place.
Now, I can slice off the extra screen, in 1/16 inch from the outside edge of the wood, with a sharp razor knife. The knife can be used to cut screens up through 20-mesh. For coarser screens and wire, the screen must be cut to the final size initially, and the awl method must be used to stretch the screen throughout the process.
Warning: Please be careful when trimming with the razor knife. I’ve worked with power tools my whole life, and I’ve never injured myself worse than I have with one of these knives. They can slip during the cutting and stitches will be necessary. Keep your “other” hand out of the way as you use the knife. All of this is supposed to be fun. Let’s keep it that way.
And, in a final step, I use more of the glue and some 1-inch, zinc-plated wire brads to install the 3/4-inch, half-round, trim strips. I like using this trim because the inner sloping edge directs the chemicals toward the screen, and the rounded profile is soft on the hands during use.
As I’m using the glue I’m careful to apply enough so that the screen ends up embedded in the glue, which is stuck to both the top and bottom wood surfaces. This ensures that even with pressure from the hands during use over the years, the screen will stay in place, good and taught and straight, instead of developing a downward bow.
But, I don’t apply so much glue that excess oozes out as the trim is applied. That would make a mess and clog some of the pores in the screen. Any excess glue that is present once the wood trim has been installed is carefully wiped off with fingertips. Paint thinner will remove glue from the screen if this is necessary.
I make sure there are no wires or screen-edges sticking out before the glue is dry. If there are, I can trim them now and seal those edges with a bit more glue.