Instructables

How to Build a Cafe-Wall Illusion Coffee Table

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Picture of How to Build a Cafe-Wall Illusion Coffee Table
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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.
 
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Step 1: How it works

Picture of How it works
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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.
shallnot2 years ago
Let us know next November if it survived the year without self-destructing due to the effects of wood movement.
HarnessedDevilry (author)  shallnot1 year ago
UPDATE:

Not quite november yet, but it's still in great shape (my friends' beer spills notwithstanding).

Granted, I live in the desert in southern AZ where it never gets that humid, so I can probably get away with worse sins than others.
HarnessedDevilry (author)  shallnot2 years ago
That's a very real possibility, although I feel that my design will resist those problems. The pieces are all very firmly glued to the mdf backing (although maybe I should have gone with thicker MDF), which will hopefully prevent splitting. The dado'ed siderails will also hopefully prevent the tabletop from torsioning too much.
tomtortoise2 years ago
Hey, im building this in woodshop and i have everything layed out but the thing is i was wondering what the best way to clamp them onto the bottom table top while the glue is drying?
(pic if you want http://gyazo.com/c5e7996b4ab0e5e121521cc52947cbc1)
HarnessedDevilry (author)  tomtortoise2 years ago
That looks awesome!

I tried to glue them up just to each other at first, and couldn't get them to come out straight- so I glued them down to a piece of MDF, while I was gluing them to each other.

To clamp horizontally, I clamped a straight board across the work table, and used a second board to press the new row (I only glued up one row+spacer at a time) against it.

To clamp vertically, I just used another long, straight board across the row, which I clamped down against the worktable on each end.

This worked for me, but since I could only get two clamps on vertically, the better thing to do would probably be to use a slightly curved caul (e.g. http://www.leevalley.com/US/wood/page.aspx?p=67309&cat=1,43838) to apply pressure across the whole row.

Does that answer your question?
Sorry for the super late reply but you helped me out a lot there and I just finished it. http://fav.me/d577itu
If you have a DA and want me to put that name in the description just send me a message.
Could I paint this design on a table top? Thanks. :) (No access to wood-working tools).
mr.frob2 years ago
Very cool! I think I want to use this pattern for my electronics workbench...
Very cool man! I think you just inspired me enough to finally try making a coffee table, haha. Did you find any other "decently easy" optical illusions that you may try after this one?
Personally, I think this may be the best of the easy-to-make illusions. I've been looking at a good decent list of illusions at http://www.michaelbach.de/ot/ .

Other possibilities are the Munker illusion (3 colors look like 4)

http://www.michaelbach.de/ot/col_Munker/index.html
and
http://www.michaelbach.de/ot/lum_white/index.html

you might also be able to make the sine illusion

http://www.michaelbach.de/ot/sze_sineIllusion/index.html

finally, the "bulging checkerboard" illusion might be possible if you could use small circles instead of the little squares (make the checkerboard, drill a hole, use maple/walnut dowels to fill)
Here's a follow-up:

RE the "bulging checkerboard" pattern I found here: http://www.michaelbach.de/ot/geom_KitaokaBulge/index.html

you might be able to make the illusion as pictured with a square mortising machine, but I don't own one (no way you could do all that by hand). I made a mock-up of the pattern with circles rather than squares in GIMP, and the illusion remains, although it doesn't seem as impressive.

It also seems like it only works at certain scales; try zooming in and out on the image. when it's a thumbnail, it looks great; when it's full-screen, it looks lousy.
bulge-checkerboard.jpg
mad_mat2 years ago
Very nice job HD :-)
Something to keep in mind when making chopping boards is that its important to only have end-grain showing. If you were to cut across the grain, you'd cut the wood fibres into short sections leading to small splinters coming free from the choppng board, not to mention blunting your knife. Check out the big chopping blocks at a butcher shop, although manufactured from smaller sized pieces of timber stuck together, they look like a huge square tree stump.

Chopping boards are relatively easy to make in the same fasion a your coffee table (which looks great btw) where you start with square timber and simply cut slices off it at whatever thickness you want your board / table. If I was going to make this coffee table, and I think I will cos its a great effect, thats probably how I'll go about it.

I loved your concernes about sharp knives, optical illusions and fingers! lol.
paqrat2 years ago
I am probably never going to build this but it looks great. Well done.
aligunome2 years ago
I was wondering if this method would be easier. In my head it makes sense but I dunno about to everyone else.
What if:
You rip the 3 maple boards and 3 walnut boards to width.
Then cut 5 strips of ash.
Glue the wood going maple, ash, walnut, ash, maple, ash, walnut, ash, maple, ash, walnut.
Cut the glued boards into long strips on the radial arm saw.
put the freshly cut wood on a piece of mdf and stagger them.
Then put strips of ash between each piece of wood.

Would that work or am I going crazy.
HarnessedDevilry (author)  aligunome2 years ago
Yes, that should work. You'd probably have more luck with it if you had your long dimension running in the opposite direction as mine (my rows are super long). I'm not sure if that would make the illusion better or worse. Get a picture, crop it both ways, and compare!
errolbert2 years ago
The table is really cool, but I'm definitely gonna build my own cross-cutting sled! A rather simple solution for getting ungainly pieces cut.

Did you get a steel bar from and particular source? Presumably you just need something that fits snugly in the groves on your table saw.
HarnessedDevilry (author)  errolbert2 years ago
Shop-made tools are enormously useful, and can be deviously clever; I don't presume to be an expert in any way. If you'd like some details on how to make them, I'd recommend Mathias Wandel's writeup, from whom I admit to stealing the idea: http://woodgears.ca/delta_saw/sled.html

There are plenty of online retailers who sell steel stock; you probably want cold-rolled steel (I used stainless, but mild steel is probably also OK). I got mine from smallparts.com through amazon, if I recall correctly. onlinemetals.com is also a good source.
I agree -- The table is truly impressive, and you should put up an 'ible for the sled as well! Nice work.
Quizicat2 years ago
This looks really cool. One question. Are the intermediate strips necessary?
Is it a structural thing or is it part of the optical illusion, or just an aesthetic preference? Thanks!
HarnessedDevilry (author)  Quizicat2 years ago
Yes, it appears that they are necessary for the illusion. However, if you google for cafe wall illusion pictures, it appears that some people leave out dividers between blocks in each row (i.e. you'd keep the long strips, but ditch the short ones) and the effect still works...
I believe from Wikipedia's description that it may be an integral part of the illusion, not sure tho so here's what i found:

"The café wall illusion is a geometrical-optical illusion in which the parallel straight dividing lines between staggered rows with alternating black and white "bricks" appear to be sloped. [...] In the construction of the optical illusion often each "brick" is surrounded by a layer of "mortar" intermediate between the dark and light colours of the "bricks"."
hascher2 years ago
This is truly beautiful work! It's given me the idea to try this to make framed wall art using paper and thin-width tape! Thanks for sharing!!
this is cool i hav a pic of the real cafe wall in this opticle illusions book i got, so its interesting and i definetly want to make it