After doing any kind of card effect in which you find the
spectator's chosen card, or even if you just want the spectator
to choose a card solely for the purpose of using the
"Invisible Pen," you end the routine in this way: You
remove an "Invisible Pen" from your pocket and hand it
to the spectator. "Be careful!" you tell him.
"This is an old fashioned pen with liquid ink in it. Don't
get any on you!"
The pen, of course, is completely invisible and only exists
in the spectator's imagination. Guide him through removing the
top and placing the top on the back of the pen. "Whoops! You
dropped it! That's OK, you didn't get ink on anything yet. Here's
the top. Just try not to drop it as you push it on the back of
the pen."
The spectator's chosen card is placed face down on the table.
"Don't touch the card," you warn, "but just write
in the air over the card. Sign your name just like you always do,
but in the air space above the card. Good! Now put the top back
on the pen. Hand me the pen. I'll just put it back in my pocket.
Any questions?"
Eventually the spectator will get around to turning over the
chosen card and find that his signature is written on the face of
the card. Give it to him to keep as a souvenir.