Here's an original concept (or so I believe) that may be adapted to many venues--celebrations, cultural events, children's shows etc., especially those involving colour schemes.
EFFECT: The performer deposits two unopened packs of toy balloons (of various colours) on the table and asks a volunteer to choose one. The bags are opened and the magician and the participant each extract three WHITE BALLOONS. The challenge is to be the first to create, inflate, and tie-off a set of RED, WHITE AND BLUE balloons out of the three white ones. For this purpose, two felt-tipped markers (one red, the other blue), are allotted to each of the contestants.
For a sort of 'head start', one of the white balloons may be inflated before the competition begins, leaving the other two to be coloured.
As the challenge ensues. the volunteer uncaps one of the pens and starts vigorously to dye one of the balloons, yet the smug magician folds his or her arms and encourages the participant to do a good job. "That's great! It doesn't have to be perfect--so long as you get some decent coverage. The ink will spread out (and get lighter) when you blow it up, anyway".
When the volunteer is finished with the colouring, and is about to inflate one of the balloons, the performer merely wields the blue marker like a wand over a WHITE balloon, raises it to his or her lips and inflates it. It visibly changes to a BLUE BALLOON. The magician ties it off and sets it on the table.
The astonished participant is entreated to proceed with colouring the remaining white balloon, but again, as soon as he or she attempts to inflate it, the performer takes the red felt-tip pen, waves it over his or her last white balloon and blows it up. It turns RED before the spectators' eyes!
SECRET: This trick requires some preparation. While the two packages of assorted, multi-coloured balloons are perfectly normal (as are the felt-tip pens), you need to have a few 'gimmicked' white balloons at the ready.
First, purchase a jar of LIQUID LATEX from a craft or art supply shop (or from a theatrical supply company that sells it for making masks, facial appliances, etc.). Preferably clear, white, or neutral in hue.
Open a pack of toy balloons and pick out a RED and a BLUE one. Pull at the balloons repeatedly prior to rigging them, so that they shall be 'pre-stretched', and easier to inflate when you go into your act.
Carefully snip the mouth of each of these balloons with a pair of scissors (approximately 1/2" from the top, but conserve at least 1/2" of the neck) and fit the truncated body onto a small tube that is slightly larger in diameter than the flaccid balloon (say, 1" in diameter). The "tube" can be anything cylindrical--a hairbrush handle, for instance.
Draw the balloon taut over the form until it can go no further without forcing (until the bottom of the tube touches the bottom of the balloon).
Now take two white balloons (of the same size and shape) and fit one over each of the coloured (red and blue) balloons that are on the forms--but make certain that the necks of the white balloons reach about 1/2" HIGHER than those of the red and the blue. Eliminate any wrinkles or air pockets by gently tugging at the balloons on the forms as needed.
Peel the lip of each of the white balloons downward an inch or so and dab some liquid latex round the circumference of the necks of the red and blue balloons with a small artist's paintbrush, being mindful to avoid getting the substance into the actual bladder of the balloon. Then fit the necks of the white balloons back in place so that the adhesive is trapped tightly between the layers. Allow to dry for several hours.
Remove the gimmicked balloons from the forms. You ought to have what appear to be two WHITE BALLOONS with a coloured balloon inside of each, secured only at the neck.
TO PERFORM: Provide two ordinary packages of assorted coloured balloons (that have at least three white ones in them) and two sets of felt-tip markers consisting of a red and a blue.
Keep the two gimmicked balloons hidden in a pocket or elsewhere, but DO NOT place them on the table, as spectators will be eager to examine them once they suspect some kind of contrivance.
Instead, lay three of the ORDINARY white balloons from the pack on the table before you, and carry on as in the effect above. There should be sufficient opportunity to switch one of the regular white balloons for a gimmicked one while the volunteer is labouring to tincture his or her first balloon.
When the moment is right, mystically gesture with the appropriately coloured pen, raise one of the gimmicked balloons to your lips and inflate it. It is best to rehearse this all-important part of the performance in order to learn just how much air pressure (breath) is required to fill up the DOUBLE-WALLED balloon. Caution is advised, as if the balloon is inflated too energetically, it could burst and ruin the routine. Teach yourself to blow it up steadily and surely.
The white balloon, being distended, shall be virtually
transparent, and the colour of the inner balloon shall become evident. Both balloons shall be snug together, producing the illusion that they are one. Tie the neck and set the balloon on the table.
Should you feel that the colour of the balloon is too pale for the crowd to distinguish, compare the shade of yours with that of the volunteer (side by side), and invite the spectators to judge which is more intense.
If someone is suddenly moved to seize the remaining white balloon before you in order to examine it, he or she shall discover that it has not been tampered with.
Again--choose your opportunity to switch the regular white balloon for the gimmicked (RED-lined) one, and dumbfound everyone in your midst!
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NOTES: For best results, use white balloons that are as thin and translucent as possible for your gimmicks. The tenuity makes for a more appreciable colour change (and renders it less difficult to engross them with the exhaust from your lungs). They should yet be opaque enough when lax to conceal the colour of the inner balloon. As for the blue and the red, they should be the most RICHLY PIGMENTED that you can find.
Initially, the latex bond (having been established on the oversized forms) shall make the necks of the balloons unusually wide, but A FEW DAYS after removing them from the cylinders, they will have shrunk to normal proportion. Set them near a moderate heat source in order to hasten the process.
Your gimmicks are going to look bulkier than empty balloons of course, so try to hide all but the head and/or tail with your hand until you begin to blow them up. Or at the very least, keep them in motion in order to deter scrutiny.