I am using 3" x 6" blank flash cards on which I print a single digit on one side and then present them face down, blank side up, to the audience. Each card has been manufactured to have a single rounded corner. I need to know which card has which digit on the underside for the arithmetic-based trick to work. Of course, the cards should look the same to the specators, including the one called up to put their finger on one of the cards (after which a sequence leads them to derive a number which just happens to be the one on the underside of the chosen card).
My first method was to shave off a corner of a card so that the position of the shave-off relative to the rounded corner that each has reveals to me the digit on the bottom. This has worked well a number of times, but the last time I did it a spectator suggested that the cards were marked. I had put them away and when she asked to examine them I smiled and said, "No." Then she hypothesized that the corners were clipped (correct!). She's a teacher at a school where I'm performing several times and I don't want to use that method again when she is there. Also, I found it difficult to ID the small clipped corners from a distance of about 6 feet, where I would prefer to stand (my eyesight isn't great).
My new method is to slightly fold the cards so that a narrow or a wide side is slightly raised. I seem to be able to see this from 6' away, depending on the lighting. I will use this next Wednesday at my next show.
This leaves me with the question for you: if this second method is easily spotted by a spectator (some are within about 3' of the performance) then what OTHER methods might be used to mark the cards. I'm reluctant to put marks on the back but will if I'm called out too often. But marks might be even worse. Ideas??

You could try using juice. It's great to see the marks from a distance. Check out NUCONcept products.

Thanks Claudio!
Are you referring to a transparent type juice such as lemon juice or something that stains more like grape or tomato juice? It would have to be put on so that the spectators wouldn't notice it. What's the best way? Size? Pattern? Thanks for the help!
Barney

Not quite and I must admit that I myself don't know what it really is, but I have bought some. You'll find some recipes here and there, but you have to be wary of out-dated formulas and expensive fraudulent products. I suggest you search this forum (using "juice mark"). Expertmagician's posts are particularly informative.

Here's a marked card with juice: http://marked-cards.weebly.com/juice--n-dust.html

The marking (7) starts roughly 4th diamond from the top and 3rd diamond from the left. The stem of the 7, finishes rouhgly 5 diamonds from the bottom. It's about 3 diamond thick. To be able to see it, make sure you're about 1 meter away and that you play with the angle of your laptop screen.

It'll take some serious training to be able to see the marks which are then easily (for a trained eye) seen from 6 foot away, but impossible to see up close.

Juice Dust has been recommended by some knowledgeable members: https://www.youtube.com/watch?v=gxircrssY64

Good luck in your search.

P.S. If you do not want to take the trouble of juicing your cards, bear in mind you could have a regular set of cards, that you could hand over for examination after the effect, if you were again in the same situation. Or, a switch might work well too, so that "pesky" teacher could examine the cards before the effect.

Do you permit yourself to touch the cards? If so, then Ian Rowland's excellent Sense of Touch book should be next on your reading list (if you are able to find a copy of this coveted tome).

Claudio: interesting stuff, but my current cards are white-backed flash cards (for educators who wish to make their own flash cards), shiny on one side (the "back") and matte on the other (where I have written a large numeral). They should appear all white, clean and identical to the spectators in a class room, a few feet away from me at the closest. I never knew about that N-dust so I appreciate the pointer!

ddyment: I turn over cards with the numerals 1, 2 and 3 on them so only the white unmarked backs are showing. There is no secret there as the spectator called upon puts their finger on one of them. At the end of the trick I ask that person to mix up the cards so the order is changed and then I call up another spectator to do the trick again, never touching them after they have been mixed up by the first spectator. However I imagine that the book you recommended will be useful for me in other situations so I'll have to look it up!

Barney

Hello, barneyS.

I am wanting to find some good card stock material that, like most decks of cards, cans be easily spread (and not stick together in clumps). I can easily find the pojer0size double-blank in playing card stock. What I'm trying to find such cards in 4" X 6" (or maybe 4" X 5"). I need the material to be "slick" (like playing card stock) and the cards must be thick enough and non-absorbent enough (like blank playing card stock) so that numbers written on one side with a large-tipped Sharpie will not soak/bleed through and or be able to see the numbers through the cards because of lighting condition(s).

I'm performing Vincen Dalbam's "Mental Numbers" from Annemann's "The Jinx"...and typical index cards are unsatisfactory because:

1. Too thin and the writing on one side can be seen from the other side, and,
2. If a sharpie is used, the Sharpie ink soaks through the card and bleeds through to the other side. At the very least, this is unsightly; at worst, you can ascertain the writing.
3. Index card stock is totally unsatisfactory for ease of handling and spreading of the cards into a nice-looking fan.

Anyone have any ideas on acceptable card stock to eliminate the above three issues, and, if so, where I can get such card stock?

Thanks for any info in these regards.

Mike

Hi Turk,
I think that my 4"x6" cards have the characteristics that you are looking for, and a box of 100 of them is pretty cheap. The box is titled "Make-Your-Own" and is from TREND enterprises, Inc., St. Paul, MN 55164 USA, www.trendenterprises.com
I bought it at a teacher supply store.
Good luck,
Barney

Barney,

Thanks for that info. It is much appreciated.

Mike

P.S. I've sent you a PM in this regard.

For very good card stock go to: http://www.lybrary.com/blank-aircushion-......762.html

Ferrymagic,
Thanks for the info. It is much appreciated.
Mike

Just to give an update on the method I am using to mark the blank-backed flash cards I use (numbers written on the face-down side) which started this thread: After a number of uses the method of slightly bending 2 of the 3 cards in the middle (opposite to each other so I can detect the difference as the overhead lights play on them) has been undetectable. 2 days ago I performed with them for 5 hours at a Maker Faire. After doing the trick some would say that the trick couldn't be done if the cards were mixed up so I said that I would turn my back, they would mix around the order and I would do the trick again. Then some people looked at the cards closely, moving them around with their fingers and no one detected the method of marking. One person noted that people's finger prints on the backs of the cards, which were slightly visible, could be a method of marking the cards and I agreed but I told them that I didn't use that. No one noticed the slight bends. If, in the future, someone DOES detect them then I'll just shrug it off and congratulate them, but the method still would have worked such a high % of the time that I expect to keep it (and try to gently clean off the fingerprints...)

My personal holy grail would be a 'marked' double blank playing card deck stacked as a hypnodeck. Although I understand how to make the juice markings for 52 cards,liquid solutions do not seem to cut it with blanks and sunglasses are are not an option for me.

Natural markings or creases are the way to go with up to six or so double blank cards.

I do not have his Sense of Touch book but Ian has released some free books on his website ( www.ianrowland.com/magic ). One of them, Tricks and Stuff has a trick titled "The Lying Game" wherein a blank card is marked in an invisible way (but you need to be able to touch it).