The Green Lantern Corps are one of the most powerful groups in the DC Universe, but one small detail implies that they might have some massive unexplored weaknesses. Even worse, it is likely that the Green Lanterns aren’t even aware of this vulnerability, as if this theory is true, it means that their basic understanding of their powers is completely wrong. The Guardians have lied to the Lanterns about many important matters over the years, but this would be their most dangerous lie yet.
The Green Lantern Corps are a group of intergalactic peacekeepers who each possess a green power ring. These rings were created by the Guardians of Oa and allow the Lanterns wielding them to perform a variety of feats based on the strength of their willpower. This often manifests in green energy constructs that are made of hard light. Or at least, that’s what the Lanterns were told. A fun bit of banter from the '90s may reveal that these constructs are made from something completely different.
In The Flash #135 (written by Grant Morrison and Mark Millar, and drawn by Paul Ryan), the Flash’s wife Linda Park is drinking from a coffee cup created by the Green Lantern Kyle Rayner when she points out that the mug makes everything taste like vinegar. While seemingly a fun little jab at Kyle’s expense, when examined further, it reveals a frightening possibility. If the ring’s constructs are actually made out of solid light, then they shouldn’t have a taste or influence how liquids contained inside them taste. A change in taste indicates a chemical reaction, and this means that the constructs must have some other component to them. Since the mug made coffee taste like vinegar, it is highly likely this component is acetic acid, which would have potentially horrifying consequences.
Since acetic acid is a byproduct of bacterial fermentation, the presence of it in the constructs implies that the Green Lanterns' rings may rely on the presence of a special type of bacteria to function. The user’s willpower could cause the bacteria to rapidly ferment, producing acetic acid as a byproduct, which the ring could then shape into constructs. If any villain figures this out and then discovers a way to kill or neutralize the bacteria, then the rings could lose all functionality, leaving the ring bearer completely helpless.
Acetic acid can also become quite unstable when exposed to heat or freezing temperatures, and concentrated solutions of it can spontaneously combust at temperatures exceeding 800 degrees Fahrenheit. Given some of the extreme temperatures that can be encountered in fighting supervillains, this means the constructs could become unstable or even combust at a crucial moment. And when acetic acid decomposes due to heat, it releases toxic gases, meaning that the constructs would poison those around them as they are failing. Even worse, acetic acid can ignite or explode when it comes into contact with a variety of compounds. While these compounds aren’t common, Green Lanterns have adventures all over the galaxy, and if a villain ever discovers this, they would have an easy way to destroy the constructs.
Of course, Kyle could have used his ring to make the mug construct Linda was using have a specific chemical structure, as this is a functionality the rings have. However, he would have no real reason to do this, and it is definitely the less interesting theory behind Linda’s statement. If the constructs do contain acetic acid, then the Guardians are putting all of their Green Lanterns at risk by not informing them how their rings really work.