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A jigsaw puzzle is a tiling puzzle that requires the assembly of numerous small, often oddly shaped, interlocking and tessellating pieces. Each piece usually has a small part of a picture on it; when complete, a jigsaw puzzle produces a complete picture. In some cases more advanced types have appeared on the market, such as spherical jigsaws and puzzles showing optical illusions.
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 commercializing jigsaw puzzles around 1760. Jigsaw puzzles have since come to be made primarily on cardboard.
Typical images found on jigsaw puzzles include scenes from nature, buildings, and repetitive designs. Castles and mountains are two traditional subjects. However, any kind of picture can be used to make a jigsaw puzzle; some companies offer to turn personal photographs into puzzles. Completed puzzles can also be attached to a backing with adhesive to be used as artwork.
During recent years a range of jigsaw puzzle accessories including boards, cases, frames and roll-up mats has become available that are designed to assist jigsaw puzzle enthusiasts.
Some jigsaw enthusiasts[who?] suggest that it is bad form (against the rules) to look at the picture on the box while working on the puzzle, but most people find it to be perfectly normal to look at the box.
Most modern jigsaw puzzles are made out of cardboard, since they are easier and cheaper to mass-produce than the original wooden models. An enlarged photograph or printed reproduction of a painting or other two-dimensional artwork is glued onto the cardboard before cutting. This board is then fed into a press. The press forces a set of hardened steel blades of the desired shape through the board until it is fully cut. This procedure is similar to making shaped cookies with a cookie cutter. The forces involved, however, are tremendously greater and a typical 1000-piece puzzle requires a press that can generate upwards of 700 tons of force to push the knives of the puzzle die through the board. A puzzle die is a flat board, often made from plywood, which has slots cut or burned in the same shape as the knives that are used. These knives are set into the slots and covered in a compressible material, typically foam rubber, which serves to eject the cut puzzle pieces.
Beginning in the 1930s, jigsaw puzzles were cut using large hydraulic presses which now cost in the hundreds of thousands of dollars. The cuts gave a very snug fit, but the cost limited jigsaw puzzle manufacture only to large corporations. Recent roller press design achieve the same effect, at a lower cost.By the early 1960s, Tower Press was the world's largest maker of jigsaw puzzles, acquired by Waddingtons in 1969.
New technology has enabled laser-cutting of wooden jigsaw puzzles, which is a growing segment of the high-end jigsaw puzzle market.
Jigsaw puzzles typically come in 300-piece, 500-piece, 750-piece, and 1,000-piece sizes; however the largest commercial puzzle has 32,256 pieces and spans 544 cm by 192 cm. The most common layout for a thousand-piece puzzle is 38 pieces by 27 pieces, for a total count of 1,026 pieces. The majority of 500-piece puzzles are 27 pieces by 19 pieces. Children's jigsaw puzzles come in a great variety of sizes, rated by the number of pieces. A few puzzles are made double-sided, so that they can be solved from either side. This adds a level of complexity, because it cannot be certain that the correct side of the piece is being viewed and assembled with the other pieces.
There are also Family Puzzles, which come in 400-piece with three different sized pieces from large to small. The pieces are placed from large to small going in one direction or towards the middle of the puzzle. This allows a family or puzzlers of different skill levels and different size hands to work on the puzzle at the same time. Companies like Springbok, Cobble Hill, Ravensburger, and Suns Out make this type of specialty puzzle.
There are also three-dimensional jigsaw puzzles. Many of these are made of wood or styrofoam 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.
Another type of jigsaw puzzle, which is considered a 3-D puzzle, is a puzzle globe. Like a 2-D puzzle, a globe puzzle is often made of plastic and the assembled pieces form a single layer. But the final form is a three-dimensional shape. Most globe puzzles have designs representing spherical shapes such as the Earth, the Moon, and historical globes of the Earth.
There are also computer versions of jigsaw puzzles, which have the advantages of requiring zero cleanup as well as no risk of losing any pieces. Many computer-based jigsaw puzzles do not allow pieces to be rotated, so all pieces are displayed in their correct orientation. These puzzles are thus considerably easier than a physical jigsaw puzzle with the same number of pieces.
Puzzle pieces 
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. The uniform-shaped fully interlocking puzzles are the most difficult, because the differences in shapes between pieces can be very subtle.
Some puzzles also have pieces with non-interlocking 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.
Most jigsaw puzzles are square, rectangular, or round, with edge pieces that have one side that is either straight or smoothly curved to create this shape, plus four corner pieces if the puzzle is square or rectangular. Some jigsaw puzzles have edge pieces that are cut just like all the rest of the interlocking pieces, with no smooth edge, to make them more challenging. Other puzzles are designed so the shape of the whole puzzle forms a figure, such as an animal. The edge pieces may vary more in these cases.
Potential Alzheimer's prevention 
According to the Alzheimer Society of Canada, doing jigsaw puzzles is one of many activities that can help keep the brain active and may contribute to reducing the risk of developing Alzheimer's disease.
World records 
The world's largest commercially-available jigsaw puzzle was released by Ravensburger AG (Germany) in September 2010. It consists of 32,256 pieces and measures 544 cm by 192 cm. The world's largest-sized jigsaw puzzle measured 58,435.1 ft² (5,428.8 m²), with 21,600 pieces. It was assembled on November 3, 2002 by 777 people in Hong Kong.
See also 
- Jigsaw puzzle accessories
- Lost in Translation (poem)
- Three-dimensional edge-matching puzzle
|Wikimedia Commons has media related to: Jigsaw puzzle|
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- "Ravensburger Shatters Record with 32,000+ Piece Puzzle". Wired. 2011-02-11. Retrieved 2011-12-07.
- Healthy Brain Alzheimer Society of Canada Accessed 30 March 2011
- "Largest commercial jigsaw puzzle - most pieces". Guinness World Records. 2010-09-01. Retrieved 2013-03-04.
- "Largest jigsaw puzzle". Guinness World Records. 2002-11-03. Retrieved 2013-03-04.