LCL is an amber-colored, translucent liquid, which allows an Eva pilot to mentally link with their Evangelion Unit. The Entry Plug of an Eva Unit, containing its cockpit, is completely flooded with LCL, and, because it is oxygenated, upon being submerged Eva pilots can "breathe" the liquid (similar to real-life experiments involving liquid breathing).
Upon Evangelion activation, an electrical current is run through the LCL and it undergoes a phase shift, after which its density, opacity and viscosity appears to approach that of air. However, the LCL remains in a liquid phase and does not undergo a transition: the pilots appear to be surrounded by air, however occasionally air bubbles will float away from their mouths, revealing that they are still in a liquid medium.
When an Eva activates, with the pilot is totally submerged in LCL in the entry plug, the LCL acts as a mediator allowing the pilot's nervous system to electro-chemically directly interface with the nervous system of an Eva. The greater the degree of interfacing between an Eva and its pilot's minds, the higher the "synch ratio" between the two.
LCL is strictly the only thing a pilot absolutely requires to synch with an Eva: plug suits "cut down on interference" but on several occasions the pilot hasn't worn one, and while Interface Headsets are much more necessary to synching, when Shinji piloted Eva-01 for the final time in End of Evangelion he did not wear an Interface Headset (although by that time he was essentially a passenger inside the Eva). Case in point, Toji and Kensuke, wearing neither plug suits nor interface headsets, manage to induce interference in Episode 03 when they enter the entry plug.
It is stated several times in the series that LCL smells "like blood". LCL is, in fact, the blood of the Second Angel, Lilith, which is restrained in the deepest level of Nerv HQ, "Terminal Dogma". The "LCL Plant" in Terminal Dogma is actually an entire lake formed from the blood of Lilith.
LCL shares similar properties with the hypothetical "primordial ooze" from which life on Earth first evolved. This is because non-Angel life on Earth actually originally evolved from the LCL spread by Lilith when she landed on Earth. During Third Impact, Lilith's Anti A.T. Field causes the A.T. Fields of human beings and all other Lilith-based life to collapse, reverting their bodies to puddles of LCL.
LCL apparently has sources in addition to Lilith's body. In Episode 20, Shinji's body reforms from LCL within the core of Eva-01. LCL is also seen escaping Eva-00's core in Episode 23' and Eva-01's (again) in Episode 26'.
An amber-colored fluid, visually identical to LCL, escapes from Leliel's body (the ultra-flat "shadow") when the bullets of Eva-01's handgun strike in Episode 16.
In Other Media
- In the Rebuild of Evangelion continuity, LCL is colored blood red, not orange.
- Here, LCL is used in a dilute form to ease the strain on the pilot. This is seen in Evangelion 2.0: You Can (Not) Advance, when Gendo increases the concentration of LCL in Shinjis cockpit to the limit in order to avoid further damage to the Geofront from his outburst after forcing Eva-01 to destroy Eva-03 using the Dummy System. The concentration increase resulted in Shinji losing conciousness, which made it possible to detain him.
- Due to its orange color, LCL is often referred to as Tang™, an orange juice drink, by fans. Instead of saying "reverting to LCL," fans will often say, "(character) was Tanged", "Tangification", etc.
- The color of LCL was changed to blood red instead of orange for Rebuild of Evangelion, thus depriving fans of further comparisons of it to Tang.
- LCL is definitely an acronym for something: other words in the series spelled using all-capital letters such as "Nerv", "Gehirn", and "Seele" are not acronyms, but instead were simply spelled using all-capitals as a quirk of translation. "LCL", however, is confirmed to be an acronym because it is sometimes seen spelled as "L.C.L." on computer displays, though simply "LCL" is much more common.
- It is unknown what the initials "LCL" stand for, but we do know what they don't mean. According to the Evangelion: Death and Rebirth theatrical program (special edition):
- "Incidentally, the widely circulated idea that L.C.L is the abbreviation of "Link Connected Liquid" is incorrect."
- However, nowhere does it say what it does mean. Why they would go out of their way to say what it doesn't stand for, but not go on to explain what it does stand for, is unknown, and a cause of much fan frustration. Evangelion Chronicle suggests that one of the Ls stands for "Lilith". In the Manga the Dossier at the beginning of a chapter states that LCL does mean "Link Connected Liquid".
- The Spanish word for "sky" or "heaven" is "El Cielo". The Sea of LCL in End of Evangelion seems to be in space. If this similarity is deliberate and not a coincidence, it makes LCL a wordplay on "heaven".
- Looking at the similarities and references of LCL to the hypothetical primordial soup of life, a possible meaning to the acronym LCL could very well be "Life Component Liquid", or a derivative thereof.
- In the Old Testament/Torah blood is equated with the lowest aspect of the soul in qabalah called nepesh (נפש). See Leviticus (ויקרא) xvii:xi and Deuteronomy (דברים) xii:xxiii.
- The LCL fluid inside of the Entry Plug is oxygenated, thus when Ramiel's energy beam strikes Eva Unit 01 in Episodes 5 and 6 and Shinji is being "boiled alive", you can see that the heat is causing all of the oxygen to bubble out of solution.