A blister pack is made by the combination of two separate sheets of material where, in one of them, cavities have been formed that allow the product to “sit in” without bulging so that the other material can be sealed on top without punching a hole in it. There are two main types of blisters used in the pharmaceutical industry: plasticaluminium and aluminium-aluminium. The former uses thermoforming to heat the plastic in a continuous motion whilst in the latter the cavities are formed by punching the aluminium in an intermittent motion. This is an intermittent-motion machine that can do aluminium-aluminium blister packs which offer better protection than plastic-aluminium blisters both as a moisture barrier as well as from light and oxygen.

 There are four stages in blister packing: forming, filling, sealing and cutting.

· Forming: The aluminium film is fed to the machine by means of a roll that is placed onto a horizontal roller on the left-hand side of the machine. The aluminium film is pulled up and passes over a metallic plate called a mould that has cavities or “pockets” according to the shape and size of the product to be packed. Another metallic plate with “punches” (protrusions) is directed with force into the aluminium and form holes in the shape and size of the tablets or capsule to be packed. This is called “cold forming” since, unlike with the use of plastic film, no heat is used. · Filling: The formed film continues to the middle of the machine where product is guided down from a hopper and falls into the cavities. A scraper ensures that no cavity has more than one unit of product. In modern factories, an inspection system is also employed to check that each unit of product is free of defects and that it is the right colour, shape and size.

· Sealing: As the filled film travels to the other end of the machine, it passes over a heated roller that also has cavities in the shape and size of the product to be packed, on top of which passes an aluminium film (containing the name and other important information on the product) which is heat-sealed onto the lower film by means of another roller.

· Cutting: The combined film containing the product then travels down and toward the lower middle section of the machine where it is cut into individual blister-packs by cutting knives of the required shape and fall either into a container for collection or onto a conveyor belt to be taken for boxing into cartons.

Blister packs are useful for protecting products against external factors, such as humidity and contaminationfor extended periods of time. Opaque blisters also protect light-sensitive products against UV rays and also make the tablets / capsules invisible to children thereby avoiding the temptation to put them in their mouth should they ever get hold of one.

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