Obviously this answer needs a disclaimer: I do not know Karate, and
neither do you. The art of "breaking" should not be attempted by
beginners - the most likely outcome is a broken bone. You should read
and understand all the principles involved, for it cannot be explained
in a sentence or two. It involves correct selection of timber or
bricks, understanding laws of motion, using precise parts of your
body, and much training.
I hope that you will start with the thinnest, driest piece of timber
you can find, and pay attention to the direction of the grain.
Something so easy a 7-year-old could break it. Then slowly and
patiently try thicker pieces.
Having said that, here are some tips and techniques I found online.
Please read everything, especially the links at the bottom which lead
to lengthy articles:
"One key to understanding brick breaking is a basic principle of
motion: The more momentum an object has, the more force it can
generate. When it hit the brick, McNair's hand had reached a speed of
11 meters per second (24 miles per hour). At this speed, his hand
exerted a whopping force of 3,000 newtowns--or 675 pounds--on the
concrete. A slab of concrete could likely support the weight of a few
people weighing a total of 675 pounds (306 kilograms). But apply that
amount of force concentrated into an area as small as a fist and the
concrete slab will break.
Another key to brick breaking lies literally in the palm of your hand.
Feel the bone on the edge of your hand, directly below your little
finger. This bone (known as the fifth metacarpal) bears the brunt of
McNair's hand strike. Human bones can actually resist 40 times more
stress than concrete. (Picture a piece of concrete the size of a bone,
and imagine how easily it would break.) The natural engineering of the
human hand also lessens the severity of the impact. The muscle,
tendons, ligaments and other soft tissue in the hand provide a natural
cushion, dispersing the impact energy up through the arm.
If you attempt brick breaking without proper training, you'll end up
with an injured hand and possibly serious nerve damage! You must be
instructed by an expert in proper technique. Proper training protects
your hand because regularly striking a striking pad or post causes
your skin to develop calluses, your muscles to strengthen, and your
bones to thicken. Extensive training is also necessary to train your
brain and muscles to bring your hand down just right--exactly as it
reaches its full speed and right smack in the center, at the brick's
"Probably the most important aspect of breaking is learning to go
through your target, not just hitting to it. Not only is that an
important concept in developing explosive power in your techniques but
I find that when one "hits through" the target no only will they be
successful in the break attempt but one will not hurt the hand or
foot. If however you merely hit to the target and stop; you will
suffer both the pain of the strike as well as the ignominy of
disappointment. To be successful, hit to a point at least several
inches beyond your target."
"We learned all about selecting the right breaking materials. Titles
had to be picked up just before a demonstration from the Marley Tile
works in Dunton Green. Fresh off the production line they were
incredibly fragile and broke as easily as a couple of digestive
biscuits. In fact, one had to be very careful not to snap them
accidentally while setting up the break. Other seasoned tiles of the
same type were left lying around lest anyone wished to examine the
material to be smashed. Bricks were selected with a care second to
none. Bricks in particular are varied and diverse. A blue gort
engineering brick is not a brick for breaking by hand. Light and soft
red bricks are. As for wood, this was specially selected in large
twelve by two-inch pine planks of ten feet or more in length. This was
then sawn up into eight inch lengths so that the grain ran across the
width of the board and not along its length.... All breaking materials
were better if very dry. Any moisture in tiles and particularly bricks
made the task of breaking very much more difficult."
"...The most troublesome were older brittle roofing tiles that had a
sand covered surface. We used these if they were donated and we could
not get fresh ones from Marley. As the hand or fist smashed into the
tiles, the abrasive surface would cause rough abrasions to the
striking part. Sometimes fragments of tile would explode and cut the
hand or forearm. Some of the cuts sustained were nasty deep gashes
that needed medical treatment."
Also, carefully read:
To Break or not to Break
Breaking (with video clips)
The Specifics of Breaking
Search Strategy: Kiai bricks
I hope you reach the status of impressive party trick without hurting