# Bubble gum

Bubble gum (or bubblegum) is a type of chewing gum, designed to be inflated out of the mouth as a bubble.

## Composition

In modern chewing gum, if natural rubber such as chicle is used, it must pass several purity and cleanliness tests. However, most modern types of chewing gum use synthetic gum-based materials. These materials allow for longer lasting flavor, a softer texture, and a reduction in tackiness.

## Mechanical properties

As a sort of chewing gum consisting of long-chain polysaccharides, bubblegum can typically exhibit linear and nonlinear viscoelastic behaviors. Therefore, the distinct deformations under chewing can be affected by shear rate, shear strain, and shear stress applied through teeth. Based on these, it is helpful to characterize the intrinsic rheological properties of chewing gums for future improvement and optimization of commercial products’ texture and chewiness.
The linear viscoelastic (LVE) property can be probed on pre-shaped gum cuds through a small isothermal strain deformation (i.e., below yield strain) under small amplitude oscillatory shear (SAOS). Here the critical yield strain is defined as the modulus deviating about 10% from its initial value. Under it, gum cuds show elastic deformation that follows power-law behavior as a critical gel in the linear regime; otherwise, exhibiting nonlinear responses with increasing shear stress (plasticity). Normally, this yield strain is less than 1%.
Regarding plastic deformation, the nonlinear viscoelasticity can be explored through shear creep experiments (relaxation time) and the start-up of steady shear stress-controlled uniaxial/biaxial extension. The former demonstrates that fractional recovery, defined as the ratio between measured strain after deformation and recovered strain without adding shear stress, for chewing gums under moderate shear stress (~ 1000 Pa) is between 25% and 40%. This relatively high fractional recovery (the ability to recover its previous shape) is consistent with providing a satisfying sensory feel. On the contrary, bubble gums only show fractional recovery lower than 15%. Therefore, bubble gums can withstand more substantial stresses before break-up than normal chewing gums. This distinction is mainly due to its on-purpose design, which allows it to form and maintain large, stable bubbles when blown up through sizeable shear stress on the tongue.
The stretching experiment shows gum cuds owning strain hardening during uniaxial extension. In particular, the LVE regime is absent with applying a constant Hencky strain rate, like the plastic flow in polycrystals or polymers. Moreover, different values of Hencky strain rates can lead to either extensional viscosity plateaus before sagging (macroscopic failure) or necking (strain hardening) following a low/high strain rate. Typically, the strain softening at a low strain rate manifests the disintegration of brittle networks within gums. In contrast, the nonuniform deformation of polymers and crystallization induced by strain explain the strain hardening behavior at a high strain rate.

## History

In 1928, Walter Diemer, an accountant for the Fleer Chewing Gum Company in Philadelphia, was experimenting with new gum recipes. One recipe, based on a formula for a chewing gum called "Blibber-Blubber", was found to be less sticky than regular chewing gum and stretched more easily. This gum became highly successful and was eventually named by the president of Fleer as Dubble Bubble because of its stretchy texture.
This remained the dominant brand of bubble gum until after WWII, when Bazooka bubble gum entered the market.
Until the 1970s, bubble gum still tended to stick to one's face as a bubble popped. At that time, synthetic bubble gum was introduced, which would almost never stick. The first brands in the US to use these new synthetic gum bases were Hubba Bubba and Bubble Yum.
Bubble gum got its distinctive pink color because the original recipe Diemer worked on produced a dingy gray colored gum, so he added red dye (diluted to pink), as that was the only dye he had on hand at the time.

## Flavors

In taste tests, children tend to prefer strawberry and blue raspberry flavors, rejecting more complex flavors, as they say these make them want to swallow the gum rather than continue chewing.

## Bubble gum flavor

While there is a bubble gum "flavor" – which various artificial flavorings including esters are mixed to obtain – it varies from one company to another. Esters used in synthetic bubble gum flavoring may include methyl salicylate, ethyl butyrate, benzyl acetate, amyl acetate or cinnamic aldehyde. A natural bubble gum flavoring can be produced by combining banana, pineapple, cinnamon, cloves, and wintergreen. Vanilla, cherry, lemon, and orange oil have also been suggested as ingredients.

## Records

In 1996, Susan Montgomery Williams of Fresno, California, set the Guinness World Record for largest bubble gum bubble ever blown, which was 26 inches (66 cm) in diameter. However, Chad Fell holds the record for "Largest Hands-free Bubblegum Bubble" at 20 inches (51 cm), achieved on 24 April 2004.

## Tourism

Bubblegum Alley is a tourist attraction in downtown San Luis Obispo, California, known for its accumulation of used bubble gum on the walls of an alley.
The Market Theater Gum Wall is a brick wall covered in used chewing gum, located in an alleyway in Post Alley under Pike Place Market in Downtown Seattle.