Smash hit

The Wong (or centrifuge) method: First, put the lid on the bottle and grip it at its base. Then swing your arm as if you were throwing a ball overarm. This method, which uses the principle behind a centrifuge, forces the ketchup to the top of the bottle, allowing you to pour it out. (Whether you can use such a flamboyant technique in a posh chippy is open to question.)

The Lloyd-Evans (or thixotropic) method: Ketchup is gloopy because it is thixotropic. This means that, when it is at rest, it has a thick gelatinous consistency that can be altered to a runny consistency by the input of energy, typically by shaking. The thixotropy is provided by the starch used in ketchup. Starch molecules come in the form of long chains and, when starch powder is mixed with water and heated or subjected to enzyme treatment, weak links are formed between the long molecules. This is what happens when the ketchup is made at the factory and there is a physical change in the ketchup, creating a pasty, gelatinous matrix. These thickening and gelling abilities of starches such as corn flour, rice flour, potato flour and powdered arrowroot are used in sauces, gravies and soups. To get the ketchup out of the bottle, first ensure that the lid is on, unless you want to upset the person sitting directly opposite you, then give the bottle some vigorous but not over-athletic shaking. This will break some of those weak bonds between the starch molecules. Now turn the bottle upside down over your plate and watch the ketchup emerge in a slow, gentle stream.

The Bellis (or vibration) method: Rapidly hit the side of the bottle with the soft edge of your fist while holding the bottle at an appropriate angle. The vibration of the rapid thumping will break down the structure as above, allowing the ketchup to flow easily. This is the same principle used to settle concrete into moulds. In the case of concrete, however, a vibrating device is probed into the mix and the rapid vibrations shake the concrete, allowing it to spread downwards into the mould.

The Hann (or temperature) method: To get a nice even coating on your chips the best thing you can do is to warm up the ketchup. Provided you remove the metal cap, a burst of no more than 15 seconds in a microwave usually does the trick. Obviously, the amount of sauce in the bottle and how chilled it was will affect the success of this method, but heat is a guaranteed way of making the ketchup runnier as the bonds between layers of molecules become easier to break with shear stress and slide past each other more easily as the temperature increases. This property of viscous fluids – the phenomenon by which their viscosity tends to fall (or, alternatively, their fluidity increase) as their temperature increases – is known as the temperature dependency of liquid viscosity.

The Goldstein (or poking) method: Take a long, thin object (a chopstick works well) and poke a hole into the ketchup through the mouth of the bottle. This breaks the air/liquid seal and lets the sauce flow freely.

The Medhurst (or ‘what-not-to-do’) method: Leave the bottle in the back of your store cupboard for a few years until fermentation sets in. Pressure will have built up inside the bottle so that when the lid is removed the sauce will eject dramatically from the opening. This certainly removes the ketchup from the bottle but whether it fulfils the ‘no splattering’ criterion is open to debate. Howard Medhurst, who suggested this method, admits that his kitchen now has a 10-cm-wide red streak across the entire ceiling, one wall and half of the floor.

PS: Ogden Nash, renowned for his witty light verse, had something to say on the subject. His granddaughter, Frances R. Smith, of Baltimore, Maryland, who is the family representative of Nash’s back catalogue, kindly supplied us with the following poem: ‘The Catsup Bottle’ (catsup being an American variant spelling of ketchup):

First a little

Then a lottle

The catsup bottle.

For more experiments go to www.newscientist.com/hamster

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