Blu-Tack is a blue, malleable, adhesive material normally purchased in sheets stored between pieces of something like industrial-strength greaseproof paper. It is commonly used for temporarily sticking one surface to another, preferably a fairly light material to pretty much anything else that's reasonably dry and not too textured. So, usually it's used to stick pictures and posters to painted or wallpapered interior walls.

Why Blu-Tack?

An oft-considered question is why is Blu-Tack blue? Or called Blu-Tack, for that matter? The most likely reason is in connection with Blue Tacks, pins used for fixing objects in place in the past, like furniture materials, clothing hems, etc. The tacks were blue due to the sterilisation fluid used¹ that was intended to prevent health problems for upholsterers and tailors who put the tacks in their mouths while working with them².

Another possible advantage in the colour is for the same reason that some brands of Band-Aid are blue - to ensure that the material is suitably visible if accidentally dropped into food³.

Material Composition

The manufacturers of Blu-Tack, the adhesive specialists Bostik, are completely closed-lipped about the composition of the material. They are willing to provide information on the material in general, but the specifics of its ingredients are a closely-kept secret.

The material is described as a synthetic rubber compound without hazardous properties under normal conditions. It's recommended that it should be stored in a cool location away from sunlight or sources of heat.

Although to be avoided, it can be swallowed without harm, except for mild stomach discomfort. It has no carcinogenic hazard or toxicity. It is not soluble in water and doesn't float in it either - with a specific gravity almost twice that of water. The material will burn under extreme heat, with a flash point⁴ of 93°C/200°F, at which point it will release quantities of carbon dioxide and monoxide, water vapour, oxides of nitrogen and toxic fumes.

Physical Characteristics

Initially, Blu-Tack is a matt blue material. It can be torn apart and rolled like clay, but maintains strong elastic qualities if pulled. Rolling the material until warm makes Blu-Tack more pliable and flexible, a state which is recommended before it is used to adhere one surface to another.

Once rolled it becomes slightly glossy. If exposed to dirt or coloured materials, through painting or inking, it will begin to progressively discolour, usually turning an unpleasant greyish-blue in the long term. Materials like paint or dirt will normally also result in small flecks and a gritty texture when rolled in the hand. The material will maintain its stickiness even if dirty, though it may become progressively more difficult, and unpleasant, to work with.

The packaging highlights that Blu-Tack may occasionally leave an oily stain. Poor quality or porous paints and wallpapers will discolour over long exposure and may begin to disintegrate. The first warning of this is normally too late when you try to remove the Blu-Tack from a wall and half of the surface appears to come with it. Without resorting to some form of solvent, which is probably going to stain the surface as well, this is pretty much impossible to avoid. Bostik suggest the use of lighter fuel or dry-cleaning fluid, both of which should be handled with extreme caution.

Blu-Tack will not adhere to wet or heavily-textured substances - like brick, for example. The material requires something that can be readily adhered to - and neither of these characteristics is helpful in this respect.

Using Blu-Tack tends to result in a slow loss of mass. While it comes away from most materials quite easily there is generally a small residue that remains and in time this is where the Blu-Tack will go⁵.

It has a very similar texture and effect on shoes as chewing or bubble gum, filling the grips in a shoe sole to ensure that it's difficult to remove easily. The easiest material to use to remove reasonably soft Blu-Tack is more Blu-Tack. If you have a stubborn piece stuck in shoes, on walls or wherever, take a chunk of fresh Blu-Tack and press it against the offending piece. It's best to use a dabbing or light rubbing motion, seeking to remove a little at a time rather than the whole lot as this can cause damage to fragile materials - like the corners of posters or cheap wallpaper.

Recommended Uses

The primary use, as stated, is to fix pictures or posters to interior walls. It is recommended that both materials involved are clean, dry and grease-free. A small piece of Blu-Tack is ideally needed for each corner of the item that is being hung. A chunk should be torn off and rolled between the palms of the hand - which should also be as clean and dry, as possible - until the material is warm. At this point small pieces should be torn from the mass and applied to the corners of the poster or picture. Once applied the item can then be positioned against the required wall or surface and the areas where the Blu-Tack has been applied pressed lightly, but firmly.

The poster or picture should ideally be as light and small as possible. Heavier items will adhere for a shorter amount of time. The weight of the object, over time, will stretch the Blu-Tack until it breaks - so heavier items will fall down more quickly than lighter ones.

It can be used as temporary filler for holes or to fix objects in place. For example, it can be used to keep small ornaments in place on a mantelpiece or fix items of equipment adhered to an action toy's hand. It can be used as an alternative to sticky tape to fix pictures into albums.

It also has uses in cleaning, providing a means to adhere to substances that need to be removed from something else. For example, it can be used to remove fluff and lint from an item of clothing or strip off a build-up of ink and paper debris from typewriter letter heads.

Other Uses

The firm, but malleable, nature of Blu-Tack means that it does have a number of uses beyond simply adhering one thing to another.

• Like clay, and similar materials, it is capable of taking an imprint from another object. It's possible to either press an object into the Blu-Tack or press it against something with a raised or printed image on it. It can be used to raise print from most run-of-the-mill newspaper (ie not the fancy ones with ink they claim doesn't rub off on your hands). It can be pressed against a coin, a piece of jewellery or something else with a raised pattern and then used as a mould for Plaster-of-Paris or used as a stamp with poster paint or ink.

• It can be used as an art material, providing a medium for Sculpting. For those with an artistic streak is can be used to make rough prototypes for models or to make interesting knick-knacks for your home or desk. It can be used by modellers or wargamers to provide impromptu props or scenery - for example, it could be used as a rock or a hill⁶ - or used to support kinks in railway track. It can be painted on and varnished for permanent use in any of these forms.

• In much the same way that clay can be used as a form of 'art therapy' for the stressed, Blu-Tack can be a highly effective means of relieving tension. Rolling, kneading, pounding, tearing - the fact that Blu-Tack can suffer any of these abuses without permanent damage means that any level of stress can be handled and it will still be there for next time.

• In schools, colleges and more playful offices Blu-Tack can be used as a projectile weapon or modelled into small handguns. Individual pieces can be thrown or flicked using fingers or a ruler. The temporary adhering nature due to weight can provide a means to create a surprise by pressing a large piece into a ceiling or on the mantle above a doorway. The weight of the piece of Blu-Tack means that eventually it will loose its grip and fall on an unsuspecting passer-by.