Tearing a deck of cards in half is another common feat of strength. It
requires intense hand strength to hold the deck in place with one hand
while the other tears it off like a paper cutter. Requires a strong
pinching grip but not necessarily in the same manner most people train
their pinch.
This is just one method of tearing a deck of cards in half, another
being to grip the deck with the hands facing the opposite way and twist
it apart.
It is a progressive
exercise as you can start with less cards and work
your way up to a full deck or even beyond. More advanced card tearing
feats involve tearing it into quarters or eights, notching the deck and
more.
Different cards will have different difficulty. You can start with
easier decks and work your way up to harder decks like the Bicycle
brand.
Some people fake this stunt by baking the cards in an oven. This would
make them brittle and easy to tear.
If you want to be able to tear cards you are going to have to get a
bunch of decks to practice with. Here is my recommended resource from
Amazon. The best part is you get a variety of decks with different
difficulty levels. And at a good price too!
If you need more information on card tearing you'll want to check out
the Card
Tearing ebook
by the Diesel Crew. It has tons of training information, covering
different techniques, how to train and much more.