In this video the effect has been sped up for clarity, however the same effect could be had with a high torque clockworks using the minute and second hand. I enjoy the subtle effect of using the hour and minute hands myself. Not sure what youtube did to the color in my video.
A moire pattern is caused by interference, more information is available here moire at wikipedia
Step 1: Gather Your Materials
You will need
A clock movement
assorted odds and ends
Start by removing your clock movement from a clock. Place your thumb against the time setting knob and gently twist off the hands, then unscrew the nut around the shaft, the movement should now be free. be sure to save the hands.
Step 2: Creating the Moire Pattern
There is a great deal of math available on the net about moire patterns, however, since it is spring break, we will forgo it. A moire pattern can be any pattern that causes an interference effect, for instance here's a moire pattern caused by the office walls where I work. Using a graphics program make any pattern you like, circles, grids, radial lines. I used radial wedges. Contrasting colors are nice too.
Step 3: Making the Dials
In this step we take our two patterns and print them out. One needs to be printed on photopaper and the other onto a transparency.
Once printed the photo paper dial will need to be reinforced by gluing, with aerosol glue, to a piece of thin cardboard.
Step 4: Mounting the Dials
At this point we'll trim the dials down to circles, the only other change we need make to the transparent dial is the addition of the minute hand, with the hand removed, to the center, attach it with super glue. Do NOT use a super glue accelerator on the transparency, the ink will run.
The photo paper dial is slightly different. For a proper moire effect we need not just rotation, but translation, so the hole will be off center. The easiest way to locate the hole is to overlay the transparency until you get the effect you like, the center of the transparency is now located where you will make the hole in the photo paper.
Once you have the hole in the photo paper dial, super glue on the hour hand and balance the dial, our little clock does not have enough torque to lift the off-balance dial. Here I used a pair of bottle caps with double sided tape. Balancing was accomplished by spinning on a pencil tip and balancing until it showed no preference in stopping.
Step 5: Final Assembly
Simply push the dials back onto the clock movement, make sure they're square and neither dial binds. Hang on the wall, and enjoy.