Oobleck is a simple mixture of cornstarch and water known as a non-Newtonian fluid. This means its viscosity, or resistance to flow, changes based on the force applied. When handled gently, Oobleck flows easily and acts like a liquid. However, applying rapid pressure, like a punch or a quick squeeze, causes the cornstarch particles to jam together, making the mixture temporarily behave like a solid. This unique shear-thickening property makes it popular for science demonstrations, but its high water content limits its lifespan.
The Typical Lifespan of Oobleck
The usable lifespan of Oobleck kept at room temperature is typically short, lasting anywhere from two to five days before its properties begin to change significantly. The primary factor limiting its longevity is water evaporation, which is a continuous process when the substance is exposed to air. As the water molecules escape into the atmosphere, the mixture’s delicate ratio of cornstarch to water becomes unbalanced. Environmental conditions, such as high temperatures and low humidity, can drastically accelerate this evaporation process. If left uncovered in a warm environment, Oobleck can dry out completely within 24 hours, reverting to a crumbly, non-responsive solid mass of cornstarch powder.
Optimal Storage Methods for Longevity
To extend the lifespan of Oobleck, the focus must be on maintaining its water content and discouraging microbial growth. The most effective strategy is to store the mixture in an airtight container, such as a sealed plastic tub or a heavy-duty zip-top bag. Creating a complete seal prevents the water from evaporating, which is the quickest way the Oobleck spoils. For longer-term storage, refrigeration can provide an extra layer of protection against biological spoilage. The cooler temperatures slow down the reproduction rate of airborne mold and bacteria that can contaminate the mixture. Even with airtight storage, the cornstarch’s organic polymer structure makes it a potential food source for microbes. If the Oobleck appears too stiff or crumbly, it has likely only lost a small amount of moisture. Slightly dried Oobleck can easily be revived by adding a very small amount of water and mixing it in slowly. This restoration process allows the cornstarch particles to re-suspend properly.
Identifying When Oobleck Has Expired
There is a distinct difference between Oobleck that is merely dried out and Oobleck that has truly expired and should be discarded. The clearest sign of expiration is biological contamination, which typically manifests as visible mold growth. Mold often appears as fuzzy, discolored spots that can be green, black, or pink on the surface of the mixture. Once these biological contaminants are visible, the Oobleck is no longer safe for play and must be thrown out. Another strong indicator of spoilage is a foul or sour odor, which signals bacterial decay of the starch. This putrid smell is sometimes compared to rotten cheese or sour milk. Additionally, if the Oobleck has separated into a layer of liquid and a hard, dense layer of cornstarch that cannot be easily stirred back together, it may have fundamentally broken down. If discoloration, mold, or a rancid smell is present, the mixture should be disposed of immediately in the trash, not down a drain, to prevent pipe clogs.