Bacta was a synthetic chemical substance that consisted of gelatinous, translucent red alazhi and kavam bacterial particles that were mixed within a colorless, viscous fluid known as ambori. When a patient was exposed to bacta, the bacterial particles within sought out wounds and promoted rapid tissue regeneration while preventing the emergence of scar tissue. Bacta was often thought of as a "miracle fluid", and seemed to be effective against almost every type of injury and ailment across an incredible cross-section of species throughout the galaxy. It was considered to be the best medicine available anywhere, with kolto as its short-lived competitor.
Bacta could be administered through disposable bacta patches, through direct injection, consumption (via bactade), through the application of a salve or out of a Bio-Bacta tank, or by submersion in a standard bacta tank. When bacta immersion was used, the patient would either be clothed in white shorts or a white gown depending on the person's gender. The method of administration depended on the severity of the wounds. It was imperative that bacta was applied in a solution of clear synthetic fluid which mimicked the body's own vital fluids.
Bacta had a smell that was described as 'sickly-sweet'; immersion in a bacta tank could leave one with the taste and smell of bacta within their mouths and nasal cavities for weeks afterward, and even bacta patches left a smelly residue, although it was weaker. Bacta tanks themselves came in two varieties: there were the large, permanent or semi-permanent tanks installed within medical facilities, as well as emergency tanks that were collapsible and portable. Such field tanks actually required the patient to lie on their backs or stomachs; the bacta within often had to be taken out and run through filters.
Bacta was invented by the Vratix on the planet Thyferra in antiquity, with the galaxy at large learning of its properties around 4,100 BBY. The Vratix were willing to share the technology, but the substance could only be made on their homeworld where the needed resources were abundant. Struggles on Thyferra were often caused by disputes over control of bacta, often between the two main producers of bacta, the Zaltin Corporation and the Xucphra Corporation, or over the bacta the planet produced. Before its obsolescence, kolto was used along with bacta for medical treatments. Bacta later outsold kolto and eventually replaced it altogether. After the reorganization of the Galactic Republic during the Clone Wars, the new Galactic Empire only allowed bacta to be produced on Thyferra, which was then stockpiled on Bespin.
At some point, Emperor Palpatine had the chemical sequence for bacta stored at his stronghold on Wayland with the possible intention being the development of a weapon designed to neutralize the properties of the compound. However, his scientists never developed a weapon and the sequence remained stored on Wayland. When the Yuuzhan Vong War gripped the galaxy, the Yuuzhan Vong conquered the planet Wayland where Shapers managed to analyze the bacta formula whereupon they created a virus that targeted the alazhi plant on a genetic level. This was in order to create a bio-weapon designed to kill anyone who was treated by bacta. However, their plans were thwarted by Klin-Fa Gi along with Uldir Lochett as well as his crew.
During the Swarm War, the Killiks staged a coup against the Thyferran government, which cut off the Galactic Alliance's supply of bacta during the Battle of Tenupe, thus crippling the medical abilities of the Alliance. During the Clone Wars, bacta dispensers were used by the Republic troops; the dispenser would hook up to a standard commando suit and dispense bacta into the suit's life support systems.
Bacta was often produced in various strengths and potencies based on many different factors. A batch's quality depended upon how the various ingredients were blended together, the site where the ingredients were produced, and the Vratix vrachen that oversaw the blending. As Thyferra was the source of almost all of the bacta in the galaxy while it was produced under the Imperial-backed duopoly of Xucphra and Zaltin, it was also the source of the strongest bacta. Such high-quality product was generally not exported; if it was, it was sold at incredibly high prices. Export-quality bacta was, typically, nowhere near as effective, meaning that more grievous injuries required longer exposure in order to be properly treated and healed.
Ashern rebels once contaminated a portion of bacta. The contaminated bacta caused allergy to bacta in all that used it. Upon discovery of the contamination, Ysanne Isard had much of it funneled into the black Market. Ton Phanan and Gil Bastra both possessed an allergy to bacta.
In terms of in-universe chronology, the earliest mention of bacta occurred in the Tales of the Jedi: Dark Lords of the Sith audio drama. It was also mentioned (later in galactic history) in Star Wars Knights of the Old Republic 3: Commencement, Part 3. However, the author, John Jackson Miller, admits that this may be a continuity error, and proposed a possible retcon, asserting that Marn Hierogryph was referring to some other thing coincidentally named bacta in the comic. The issue was resolved with a reference in The Essential Atlas to bacta's discovery about a century before the Tales of the Jedi series.
There is some controversy as to bacta's color. Many official sources have indicated that bacta is blueish in hue and pictures provided on LFL seem to strengthen this claim. Rumor has it that it only appeared clear in The Empire Strikes Back because of the lighting and camera angles. In the novelization of The Empire Strikes Back, it says that bacta was a thick red liquid.
Kolto tanks were the predecessor to bacta tanks, and of course were later replaced in favor of bacta, which explains the similarity in appearance between the two.
The Bacta tank was likely inspired by Dr. John Lilly's flotation tank, a vertical soundproof tank of warm salt water, first created in 1954. This device, first used by neuro-psychiatrists to study the Human brain, was later used for therapeutic benefits and referred to by Peter Suedfeld and Roderick Borrie as Restricted Environmental Stimulation Therapy. John Lilly was an adviser to George Lucas in the late 1970s.
Para-aminobenzylbacta, often abbreviated as PABB, was an organic regenerative chemical.
Marketed by Suerth Biochemicals as the "third-generation bacta" after kolto and bacta, PABB was a chemical derivative of the standard massive biopolymer bacta. However, its organic modifications greatly increased the yield of PABB in terms of tissue regeneration.
While only slightly more effective at treating standard battlefield wounds than standard bacta, PABB had a greatly enhanced yield at limb regeneration, with trace enzymatic functions that made controvertible stem cell treatment an obsolete option for dismembered soldiers. Two weeks of complete immersion in PABB could lead to complete limb regeneration, and an enhanced basal metabolic rate in the regenerated limbs for most species, including humans - matching the remarkable Wookiee feat of regenerating limbs in two weeks.