How to Build a Cafe-Wall Illusion Coffee Table

I wanted to see what I could pull off in the way of illusions, with fairly simple carpentry techniques. After some research, I settled on the cafe-wall illusion. With a repeating pattern of light and dark squares (yes, they are squares- all angles are 90 degrees), the illusion of bending appears.

I never think my projects are going to be interesting, so I don't take mid-project pictures. So I apologize if my intermediate steps are unclear due to lack of pictures. Feel free to drop me a line and I'll try to explain what I did in more detail.

I've entered this project to the Epilog contest, so please vote for me if you think I deserve it. As a university student, I'd probably drag it on-campus, and set it up to allow other students to use it for free/at cost for their projects, personal and professional. I know I've got a whole bunch of ideas I've been sitting on without the extra cash to burn on laser/CNC cutting; I'm sure others here do too.

The basis of this pattern is rows of alternating light and dark squares, each offset by about 1/2 square from the next. The rows alternate back and forth- forward two steps, backward two steps, repeat.

Also, a key aspect is an intermediate color (in my case, grey-ish) in between the squares.

Materials:

For this table, I used three different woods. You can use whatever you want, but you need two with significantly different colors, and a third that is in-between. In my case, I went with white-black-grey. To get this, I used:

• (Black) Walnut
• Hard (White) Maple
• Ash (grey- I wandered the lumberyard and picked the grey-est board I could find)
• 1/4" MDF sheet, somewhat larger than the ultimately desired shape

I exclusively used 4/4 lumber (that's actually around 2 cm thick, for you non-americans), although some thicker wood would have been nice for the legs- I just laminated two pieces for those.


Tools:

I made every cut on my table saw, using a fence and a cross-cut sled (I won't go into all the details of how to make one-it's fairly self explanatory, and you can always look elsewhere for details). You can probably use a chop/miter saw instead of a cross-cut sled, but you'll still need a tablesaw to rip your boards into the right width. Given all the cuts you'll be making, I strongly advise you avoid hand-tools here.

You'll want a modest pile of woodworking clamps, as well as a pair of nice straight-edges to clamp across the whole row. A nice straight board will do well- I'd recommend giving it a layer of furniture wax to keep it from getting accidentally glued to the workpiece. you can always remove it later if you want to use the board in something.

If you don't have access to the power tools, you might be able to get someone to do the cuts for you; I think many woodworking stores (like the one I go to) have shops for doing custom jobs. If you're just getting started in woodworking, have no fear; this project is about as simple as things come- it's just lots of repetition. There's no fancy cuts anywhere.

I went with squares about 2 inches on a side; the size isn't critical. Clean up the sides (get rid of rough edges, ensure all sides are 90^o from each-other), and rip all the walnut and maple boards to the width you've chosen. Also cut the ash boards into thin strips, maybe 1/8"-3/16" or so (I didn't really experiment here- just eyeballed something that seemed right relative to the size of the squares). You'll need several long strips of the intermediate wood, and lots of short ones, so make sure you've got enough.

Once everything is cut to the right width, set up your crosscut sled or miter saw with a stop so you can easily cut all your boards to the right length. Once you hit a rhythm, you should be able to churn out squares very fast- I also stacked the ash strips to cut them 3 or 4 at a time, although I don't know if that would work on a chop saw.

I tried to just glue them to eachother, but that failed miserably. So I used a thin sheet of MDF as a bottom, and glued them down to it, and to each-other. Lay up one row at a time, remembering to intersperse the thin spacing strips. Once the layer is completed, add a long strip on the side.

Then clamp it all together. I had the whole thing up against my tablesaw fence (nice and straight!), with a long straight-edge clamping against it. I had one long clamp across the whole row, and another straightedge across the top, clamping down the row. I allowed each row to set-up before I added the next one.

You'll have rows starting and stopping in different places; just make sure the surface is at least as big (or bigger) in every dimension as you want.

Once you've finished all the layers you want, put it back into the tablesaw. Trim the long edge(s) (you should have mdf overhanging on three sides if you went with my layup scheme). The short edges are a bit trickier- luckily, my tabletop just barely fit into the crosscut sled.

From here, you can go anywhere with this. I had initially planned to use it as a jumbo cutting board, but nixed that idea (confusing optical illusions, sharp knives, and fingers didn't seem like a good combination).

My minimalist coffee table is quite simple: I took some extra 2" wide maple, and dado'ed it lengthwise so the tabletop would fit snuggly inside. I made 4 pieces of this maple, for each side. For the legs, I took four pairs of 1-3/4" walnut boards and laminated them together (so I got 4 leg pieces with a square cross-section), and turned them into octagons using my jointer (you could just keep 'em square if you don't have one). I finally created a recess (I don't know the technical term) in the legs for the corner of the table to fit inside. I did this manually, using a hammer and chisel. There might be a better way, since I seemed to keep chipping off the top of the table-leg (the part that sticks out over surface of the table). It wasn't too bad, since I could just re-glue it, though.

Sand everything, and finish to your tastes. I used walnut oil, personally.

I think the optical illusion turned out very well, and the table's fairly sturdy- I can sit on it, although I wouldn't rough-house on it. Living in the desert, my main complaint with my table design is the sharp inside edges (where the maple edges and walnut legs meet the tabletop) tend to collect dust. I'd suggest either filling in this area with a custom sheet of glass, or sloping the border to avoid this nook.

I used a hand plane to do most of the smoothing of the table, and I hit a snag I made for myself; I shuffled all the squares in the course of cutting them, so all the grain ended up being randomized. I think it would probably look a lot nicer if you kept track of all the pieces relative positions (even better, make all the squares from one piece of walnut and one piece of maple, if possible, and keep them all in the same relative position). It would also make smoothing and finishing it easier.