Using mirrors to create illusions on a live stage has been an art form and principle used for 150 years. The techniques behind it have been refined over the years, though the basic principles still remain the same in creating the illusion of open space under a table, disembodied heads, or apparitions. Through the basic processes invented by Henry Dircks and John Henry Pepper in the 1860’s, to the variances on these famous techniques, here are the steps needed to create effective illusions using mirrors:
Open Table Illusion
Find two moderately-sized rectangular mirrors, particularly ones that have the same width of a small table. All mirror sizes are relative, depending on the size of the person taking part in the illusion.
Obtain a round-top table with four legs that’s equal width of the two mirrors.
Turn the round-top table so that one of the table’s legs is angled to the front where the audience is viewing. With a round-top table, an audience member won’t be able to know the table was turned at an angle, unlike a square table.
Place one mirror to the bottom left of the table at a 45 degree angle between the leg in the front and the leg to its left.
Place the other mirror at a 45 degree angle to the bottom right between the table leg at front and the leg to its right. Both mirrors should be facing away from each other in a V formation, with the point facing your direction.
Present your table in a location that has the same color pattern or wallpaper on the floor and all three walls. The fourth wall is open and where the audience will be viewing.
View from the audience to make sure the table is giving the illusion of having only three legs. The fourth leg won’t be seen due to the mirrors hiding it, but the audience will see it as an optical illusion and assume the fourth leg is behind one of the other legs.
Check to make sure the mirrors under the table are correctly reflecting the walls on the left and right. Reflecting properly, it gives the illusion of seeing right through the table to the back wall with the same color pattern or wallpaper.
Crouch down behind the table to below the top edge of each mirror. Find an observer to make sure you’re rendering yourself invisible so you can make objects appear alive on the table without anybody underneath abetting the action.
Consider a variation on this trick, such as cutting a hole in the top of the table to give the illusion of a talking head placed on the table’s surface.
Keep all mirrors for mirror illusions spotless, or the illusion will be given away by fingerprints and other smudges.
Consider more complex ideas with mirror illusions (see references 1 & 2), including the larger plate-glass mirror set at 45 degrees in a uniformly-patterned enclosed stage that reflects the ceiling. Use a glass cutter to cut a hole in the larger mirror to fit your head through. This creates the eerie illusion of a floating head.
Study the principles of Pepper’s Ghost (see resource 1) that are used in Disneyland’s Haunted Mansion and many other shows using ghost-like effects. Learn the difference between plate-glass projection and direct mirror reflection. Both are used interchangeably in the Pepper’s Ghost effect.
Place a soft cloth around the opening of the large plate-glass mirror for safety if you stick your head through to create the floating head illusion.
Keep your mirrors in a safe place if you're touring with a show using these illusions. They can easily break, and it's best to bring along replacements.