A jigsaw puzzle is a type of jigsaw puzzle that requires the assembly of many small, usually odd-shaped, interlocking and inlaid pieces. Each piece usually has a small part of the picture; when completed, the puzzle will generate a complete picture. In some cases, more advanced types have appeared on the market, such as spherical puzzles and puzzles that display optical illusions.
The puzzle was originally created by drawing a picture on a flat rectangular piece of wood, and then using the puzzle to cut the picture into small pieces, hence the name. John Spilsbury, a cartographer and engraver in London, commercialized puzzles around 1760. Since then, puzzles have been mainly made of cardboard.
Typical images found in jigsaw puzzles include scenes from nature, buildings, and repeated designs. Castles and mountains are two traditional themes. However, any kind of picture can be used to make jigsaw puzzles; some companies propose to turn personal photos into jigsaw puzzles. The completed puzzle can also be attached to the backing with adhesive and used as a work of art.
In recent years, a series of puzzle accessories have appeared, including boards, boxes, frames and roller shutters, designed to help puzzle lovers. Some puzzle enthusiasts think that it is bad form (violating the rules) to look at the pictures on the box while the puzzle is in the puzzle, but most people think that it is completely normal to look at the box.
Most modern puzzles are made of cardboard because they are easier and cheaper to mass produce than original wooden models. An enlarged photo or printed copy of a painting or other two-dimensional artwork is glued to cardboard before cutting. The plate is then fed into the press. The press forces a set of hardened steel blades of the desired shape through the plate until it is completely cut. This process is similar to using cookie cutters to make special-shaped cookies. However, the forces involved are much greater. A typical 1000 piece puzzle requires a press, which can generate up to 700 tons of force to push the tool of the puzzle mold through the board. The jigsaw mold consists of a flat plate, usually made of plywood, with cut or fired grooves in the same shape as the knives that will be used. These knives are placed in the slot and covered on a compressible material, usually foam rubber, whose function is to eject the cut puzzle.
New technology makes laser cutting of wooden puzzles possible, which is a growing segment of the high-end puzzle market.
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.
Since the earliest days of jigsaw puzzles the manufacturers have constantly endeavoured to create new cutting styles that differentiate their work. Even among modern, mass-produced puzzles there is considerable variation in the size, shape and intricacy of individual pieces.
The method of cutting pieces varies from puzzle line to puzzle line. 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. Larger puzzles are commonly cut into two or more sections.
More recently, technology such as computer controlled laser and water-jet cutting machines have been used to give a much wider range of interlocking designs in wood and other materials. These methods, however, have the undesirable effect of removing a small amount of material giving a loose fit with the adjoining 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 the roller jigsaw Puzzle machine (https://www.alibaba.com/product-detail/Roller-style-Jigsaw-puzzle-machine-TYC30_60288780681.html?spm=a2747.manage.0.0.1f1c71d2lIwMJb) achieve the same effect, at a lower cost.
The most commonly-used approach to building a puzzle is to start by separating the edges from the inside pieces. Once the edges are connected it is easier to move inward. For those new to puzzles, it is recommended to choose one consisting of multiple areas with contrasting designs and colors. This enables the narrowing down of potential portions of the puzzle where a particular piece will fit.
One puzzle solving strategy is the use of the picture on the box as a guide. Once the edge is completed and the location of a particular piece is discovered (in the picture), it can be placed inside the overall puzzle at the approximate location it belongs. Done enough times and, eventually, interlocking the pieces will be possible.
Another approach is to sort the pieces by color, and work on one color at a time. When working large areas with the same color (such as the sky in many landscape puzzles), shape is important. All the pieces of a particular color can be laid in a grid and tried against other pieces in the grid.
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