How Safety Match is Made

A match is a small stick of wood or strip of cardboard with a solidified mixture of flammable chemicals deposited on one end. When that end is struck on a rough surface, the friction generates enough heat to ignite the chemicals and produce a small flame. Some matches, called strike-anywhere matches, may be ignited by striking them on any rough surface. Other matches, called safety matches, will ignite only when they are struck on a special rough surface containing certain chemicals.

History

In 1831, Charles Sauria of France developed a match that used white phosphorus. These matches were strike-anywhere matches and were much easier to ignite. Unfortunately, they were too easy to ignite and caused many unintentional fires. White phosphorus also proved to be highly toxic. Workers in match plants who inhaled white phosphorus fumes often suffered from a horrible degeneration of the jawbones known as "phossy jaw." Despite this health hazard, white phosphorus continued to be used in strike-anywhere matches until the early 1900s, when government action in the United States and Europe forced manufacturers to switch to a nontoxic chemical.

In 1844 Gustaf Pasch of Sweden proposed placing some of the match's combustion ingredients on a separate striking surface, rather than incorporating them all into the match head, as an extra precaution against accidental ignition. This idea—coupled with the discovery of less-reactive, nontoxic red phosphorus—led J. E. Lundstrom of Sweden to introduce safety matches in 1855. Although safety matches posed less of a hazard, many people still preferred the convenience of strike-anywhere matches, and both types continue to be used today.
 

Raw Materials

Woods used to make matchsticks must be porous enough to absorb various chemicals, and rigid enough to withstand the bending forces encountered when the match is struck. They should also be straight-grained and easy to work, so that they may be readily cut into sticks. White pine and aspen are two common woods used for this purpose.

Once the matchsticks are formed, they are soaked in ammonium phosphate, which is a fire retardant. This prevents the stick from smoldering after the match has gone out. During manufacture, the striking ends of the matchsticks are dipped in hot paraffin wax. This provides a small amount of fuel to transfer the flame from the burning chemicals on the tip to the matchstick itself. Once the paraffin burns off, the ammonium phosphate in the matchstick prevents any further combustion.

The heads of strike-anywhere matches are composed of two parts, the tip and the base. The tip contains a mixture of phosphorus sesquisulfide and potassium chlorate. Phosphorus sesquisulfide is a highly reactive, non-toxic chemical used in place of white phosphorus. It is easily ignited by the heat of friction against a rough surface. The potassium chlorate supplies the oxygen needed for combustion. The tip also contains powdered glass and other inert filler material to increase the friction and control the burning rate. Animal glue is used to bind the chemicals together, and a small amount of zinc oxide may be added to the tip to give it a whitish color. The base contains many of the same materials as the tip, but has a smaller amount of phosphorus sesquisulfide. It also contains sulfur, rosin, and a small amount of paraffin wax to sustain combustion. A water-soluble dye may be added to give the base a color such as red or blue.

The heads of safety matches are composed of a single part. They contain antimony trisulfide, potassium chlorate, sulfur, powdered glass, inert fillers, and animal glue. They may also include a water-soluble dye. Antimony trisulfide cannot be ignited by the heat of friction, even in the presence of an oxidizing agent like potassium chlorate, and it requires another source of ignition to start the combustion. That source of ignition comes from the striking surface, which is deposited on the side of the matchbox or on the back cover of the matchbook. The striking surface contains red phosphorus, powdered glass, and an adhesive such as gum arabic or urea formaldehyde. When a safety match is rubbed against the striking surface, the friction generates enough heat to convert a trace of the red phosphorus into white phosphorus. This immediately reacts with the potassium chlorate in the match head to produce enough heat to ignite the antimony trisulfide and start the combustion.

Match boxes and match books are made from cardboard. The finned strips of cardboard used to make the matches in match books are called a comb.

The Manufacturing (Safety match production line)

Process

Matches are manufactured in several stages. In the case of wooden-stick matches, the matchsticks are first cut, prepared, and moved to a storage area. When the matchsticks are needed, they are inserted into holes in a long perforated belt. The belt carries them through the rest of the process, where they are dipped into several chemical tanks, dried, and packaged in boxes. Cardboard-stick matches used in match books are processed in a similar manner.

Here is a typical sequence of operations for manufacturing wooden-stick matches:

Cutting the matchsticks

1 Logs of white pine or aspen are clamped in a debarking machine and slowly rotated while spinning blades cut away the outer bark of the tree.
2 The stripped logs are then cut into short lengths about 1.6 ft (0.5 m) long. Each length is placed in a peeler and use our rotary cutting machine to form a long, thin sheet of wood from the outer surface of the log. This sheet is about 0.1 in (2.5 mm) thick and is called a veneer. The peeling blade moves inward toward the core of the rotating log until only a small, round post is left. This post is discarded and may be used for fuel or reduced to wood chips for use in making paper or chipboard.

Stripped logs are placed in a peeler, which cuts a sheet about 0.1 in (2.5 mm) thick, called veneer, from the log. The veneer proceeds to the chopper, which cuts it into small sticks. The sticks are soaked in a dilute solution of ammonium phosphate and dried, removing splinters and crystallized solution. The matches are dumped into a feed hopper, which lines them up. A perforated conveyor belt holds them upside down while they are dipped in a series of three tanks. The matches are dried for 50-60 minutes before they are packaged.

3 The sheets of veneer are stacked and fed into a chopper. The chopper has many sharp blades that cut down through the stack to produce as many as 1,000 matchsticks in a single stroke.

Treating the matchsticks

4 The cut matchsticks are dumped into a large vat filled with a dilute solution of ammonium phosphate.
5 After they have soaked for several minutes, the matchsticks are removed from the vat and placed in a large, rotating drum, like a clothes dryer. The tumbling action inside the drum dries the sticks and acts to polish and clean them of any splinters or crystallized chemical.
6 The dried sticks are then dumped into a hopper and blown through a metal duct to the storage area. In some operations the sticks are blown directly into the matchmaking facility rather than going to storage.

Forming the match heads

7 The sticks are blown from the storage area to a conveyor belt that transfers them to be inserted into holes on a long, continuous, perforated steel belt. The sticks are dumped into several v-shaped feed hoppers that line them up with the holes in the perforated belt. Plungers push the matchsticks into the holes across the width of the slowly moving belt. A typical belt may have 50-100 holes spaced across its width. Any sticks that do not seat firmly into the holes fall to a catch area beneath the belt and are transferred back to the feed hoppers.
8 The perforated belt holds the matchsticks upside down and immerses the lower portion of the sticks in a bath of hot paraffin wax. After they emerge from the wax, the sticks are allowed to dry.
9 Further down the line, the matchsticks are positioned over a tray filled with a liquid solution of the match head chemicals. The tray is then momentarily raised to immerse the ends of the sticks in the solution. Several thousand sticks are coated at the same time. This cycle repeats itself when the next batch of sticks is in position. If the matches are the strike-anywhere kind, the sticks move on to another tray filled with a solution of the tip chemicals, and the match ends are immersed in that tray, only this time not quite as deeply. This gives strike-anywhere matches their characteristic two-toned appearance.
10 After the match heads are coated, the matches must be dried very slowly or they will not light properly. The belt loops up and down several times as the matches dry for 50-60 minutes.

Packaging the matches

11 The cardboard inner and outer portions of the match boxes are cut, printed, folded, and glued together in a separate area. If the box is to contain safety matches, the chemicals for the striking strip are mixed with an adhesive and are automatically applied to the outer portion of the box.
12 When the matches are dry, the belt moves them to the packaging area, where a multi-toothed wheel pushes the finished matches out of the holes in the belt. The matches fall into hoppers, which measure the proper amount of matches for each box. The matches are dumped from the hoppers into the inner portions of the cardboard match boxes, which are moving along a conveyor belt located below the hoppers. Ten or more boxes may be filled at the same time.
13 The outer portions of the match boxes move along another conveyor belt running parallel to the first belt. Both conveyors stop momentarily, and the filled inner portions are pushed into the outer portions. This cycle of filling the inner portions and pushing them into the outer portions is repeated at a rate of about once per second.
14 The filled match boxes are moved by conveyor belt to a machine, which groups them and places them in a corrugated cardboard box for shipping.
Quality Control

The chemicals for each portion of the match head are weighed and measured exactly to avoid any variation in the match composition that might affect performance. Operators constantly monitor the operation and visually inspect the product at all stages of manufacture. In addition to visual inspection and other normal quality control procedures, match production requires strict attention to safety. Considering that there may be more than one million matches attached to the perforated belt at any time means that the working environment must be kept free of all sources of accidental ignition.