A jigsaw puzzle is a tiling puzzle that requires the assembly of numerous small, oddly shaped interlocking pieces. Each piece has a small part
of a picture on it; when complete, a jigsaw puzzle produces a complete picture.
The French term for jigsaw puzzle is "casse-tete", or
"break-head", referring to the imputed difficulty of solving.
Jigsaw puzzles were originally created by painting a picture on a flat,
rectangular piece of wood, and then cutting that picture into small pieces with a jigsaw, hence the name. John Spilsbury, a London mapmaker and engraver, is credited with creating the first jigsaw puzzle around 1760.
Most modern jigsaw puzzles are made out of cardboard, since they are easier and
cheaper to mass produce. An enlarged photograph or printed reproduction of a
painting or other two-dimensional artwork is then glued onto the cardboard before cutting.
The pieces are punch-cut with complex metal dies.
Typical images found on jigsaw puzzles include scenes from nature, buildings, and repetitive designs. Castles and
mountains have long been two of the favorite subjects. Many people solve jigsaw
puzzles as a hobby.
Children's jigsaw puzzles come in a great variety of sizes, rated by the number of pieces. Adult jigsaw puzzles typically come in 500-piece, 750-piece, and 1,000-piece sizes, and even more, currently the
biggest commercially available size is 18,000 pieces. These are not the exact counts, which always slightly exceed these. The
most common layout for a thousand-piece puzzle is 38 pieces wide by 27 pieces, for a total count of 1,026 pieces. The majority of
500-piece puzzles are 27 pieces by 19 pieces.
The method of cutting pieces varies from puzzle line to puzzle line. Many puzzles are termed "fully interlocking". This means
that adjacent pieces are connecting such that if you move one piece horizontally you move all, preserving the connection.
Sometimes the connection is tight enough to pick up a solved part holding one piece.
Some fully interlocking puzzles have pieces all of a similar shape, with rounded tabs out on opposite ends, with corresponding
blanks cut into the intervening sides to receive the tabs of adjacent pieces. Other fully interlocking puzzles may have tabs and
blanks variously arranged on each piece, but they usually have four sides, and the numbers of tabs and blanks thus add up to
four.
Some puzzles also have pieces with noninterlocking sides that are usually slightly curved in complex curves. These are
actually the easiest puzzles to solve, since fewer other pieces are potential candidates for mating. However, a solved part is
easily messed up by accidental shock etc.
The uniform-shaped fully interlocking puzzles are the most difficult, because the differences in shapes between pieces can be
very subtle. Occasionally, some puzzles have bizarre cuts to make solving more interesting.
Two puzzles of the same size and series from the same manufacturer usually have exactly the same cut, since the cutting dies
are complex and expensive to make and so are used repeatedly from puzzle to puzzle. This enables disparate puzzles to be combined
in odd ways. Bigger puzzles commonly are also divided into two or more sections, sometimes rotated against each other, that were
cut with the same standard-sized die.
A few puzzles are made double-sided, so that they can be solved from either side, which adds a level of complexity, because
one can't be certain that the correct sides of the pieces are being viewed.
Some people glue completed puzzles to a backing for permanent display. This is a fairly rare practice today, but was more
common at a time when puzzles were more of a novelty.
There are also three-dimensional jigsaw puzzles. Many of these
are made of wood and require the puzzle to be solved in a certain order; some pieces will not fit in if others are already in
place. Also common are puzzle boxes: simple three dimensional jigsaw puzzles with a small drawer or box in the center for
storage.
The (U.S.) National Jigsaw Puzzle Championship (http://home.att.net/~mike_helland/njpc.html) was formerly held in Athens, Ohio in 1982-87 and 1990.
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