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One summer back in the early 1970's, my grandfather took an empty tomato juice can, a piece of window glass and some tape, then put them all together in a way that made my time at the cottage that year one of the best. His glass-bottomed can -- dubbed the underwater viewer -- let me and my sister peer clearly into the shallows, getting to know the crawfish, minnows, clams and water-wigglers that lived there.
Following in Grandpa's tradition, I made my own kids some underwater viewers, and I'm pleased to say these simple playthings are still as popular 25 years after the original. The one you see here is held by my 9-year old, Robert. It's made from the same size juice can that Grandpa used, with small refinements that make it easier to build, safer to use and more reliable. The clear bottom pane is shatterproof acrylic plastic instead of glass (Plexiglas and Lexan are two brand names), and the waterproof seal between it and the can is made using silicone caulking and several wraps of a new kind of self-fusing tape that's great for lots of other things, too. You can get both at hardware stores. The tape is usually sold as a plumbing repair product. It's thicker than other kinds of tape, with a peelable backing that prevents fusing to itself on the roll. Most glass shops carry acrylic plastic, but if you can't find any locally, order it from Lee Valley Tools (800-267-8767). They carry the tape, too.
Start work with a washed juice can, one that's had both ends removed using a can opener. Use pliers to flatten any sharp edges around the inside of each opening, then trace the can's circular end onto your
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plastic using a pencil. All brands of acrylic come with peelable, factory-applied paper on both faces, both for protection and to reduce the chance of damage while cutting. A handheld jigsaw with a fine-toothed blade, or a coping saw, does a great job sawing-out your lens. You can't do that with real glass!
When you're done cutting, peel the paper from one side only of the acrylic, then set it aside on your workbench, paper side down. With the juice can sitting upright, lay a continuous bead of silicone caulking all around the rim. Any breaks in the bead will cause leaks later, so be careful. Use a traditional formulation of silicone -- the kind that smells like vinegar. I've tried low-odour and paintable versions, but they don't hold the clear plastic reliably.
Now nestle the peeled side of your lens down into the silicone, rotating it a bit to spread the caulking. Let it dry for at least 12 hours before you go onto the next step.
Painting the viewer isn't necessary, but color is nice. With the outside face of the lens still covered in paper, spray or brush on some exterior metal paint. A couple of coats will do. When this has dried, peel off the paper and get out your roll of self-fusing tape.
Peel off some backing, then wrap the tape over the joint between the lens and the can. Self-fusing tape isn't very sticky, so you'll have to hang onto the end until you get a couple of complete wraps in place. Stretching the tape as you put it on helps it conform to the 90-degree outside corner of the can and lens, and also helps it to self-fuse better. In a couple days the tape will have formed a continuous ring that'll hold the lens in place better than the silicone alone. Just what the little people in your life need to have a great summer by the water.
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