Enchantment

The technical definition of enchanting an item, according to the Epacsi, is to give it additional properties through magically linking it to an arbitrarily plane with altered laws of reality.

Enchantment is a relatively young practice, only truly becoming a field a few centuries after the Age of Myths' end. It's commonly confused with artifice, which creates superficially similar results with dramatically different methods and philosophies.

Compositions

A composition is a mix of multiple extremely finely ground elemental dusts which when together, form a magical signature linked to a portion of Chaos which grants the relevant properties. An elemental dust does not necessarily have to consist of a single atoms- quartz dust is silicon dioxide. Dusts from complex molecules do not necessarily have any correlation with their base elements, bronze dust having no relation with the Plane of Blood for example. Every dust has a series of ideas associated with it, empirically derived over time. The true nature of what the dusts actually represent and correspond to is unknown beyond these vague concepts.
Note that a dust being associated with characteristics similar to an elemental plane do not necessarily link the two- the Plane of Fire is hardly the only place in the magical universe which contains heat. Simply distributing a composition and then magically charging the piece will not grant it any additional properties.
Top-quality elemental dusts are generally ground with mithril tooling, as mithril cannot contaminate samples. Additionally, they are stored in vacuums to maximize purity- dust below the coherency limit simply results in a weaker form of the same connection so long as it's in a vacuum, as it simply results in a lower density of the same material.

Catalysts

Most materials have higher imbuement states which lack any sort of dimensional linkage. In order for them to take in magical charge and convert it to dimensional linkage, one generally requires a catalyst material which naturally gravitates towards doing so when taking in magic. Graphite, being carbon, is one of the most common examples of this for three reasons- stability, neutrality and cheapness. Due to the fact that it links to the human plane, it acts as a dimensional anchor to reduce the effects of other reagents along with its function as a catalyst. It consequently does not push any traits onto the item, making them lean more towards 'earth normal' than anything. Diamond is an odd structure of carbon in that it does the opposite, strengthening other dimension's links while acting as a catalyst. Diamond is rarely made use of, as the increase in volatility makes compositions extremely difficulty to work with. On top of that, diamond dust is ludicrously expensive- obtaining the raw material is only the first part, the energy and tooling requirements to grind it into near-molecular size constitutes the bulk of its cost.
Charcoal acts as a decent substitute for graphite- famous anecdotes have charcoal pencils be ground up in moments of desperate inspiration. However, it's definitely sub-optimal due to the potential for impurities.
Other catalysts are often used when their dimensional properties are desirable, though they are generally far more expensive than graphite and tend to have undesirable aspects. Compositions generally require at least half of their total volume to consist of catalyst(s).

Origins

The origins of enchantment can be traced back to the ancient binding practices of the north (and now Whirlpool). Next in its heritage came the development of arcanism, which the Midlanders were always fascinated by: both cultures had extremely positive attitudes towards light. One due to its necessity in maintaining livable conditions; the other from its association with fire. While arcanism and its effects were considered beautiful, it was also taboo: midlands culture traditionally has very strong sentiment against manipulating one's soul (likely stemming from historically bad relations with Eidel and their heavy use of grotesque, soul-modifying magic). In a way, its forbidden nature likely only increased its appeal to curious minds. As technology improved, some individuals on the western border of the empire find a way to generate hard light and such without direct input from the soul: so began the Age of Enchantment.