Chrism is a compound rather than a single substance, olive oil mixed with balsam or another fragrant resin, and the mixing itself is only the preparation, not the consecration.
Who is permitted to bless it
Only a bishop may consecrate chrism, and in Catholic and Orthodox practice this happens once a year at a dedicated service, the Chrism Mass, usually on Holy Thursday, when a bishop blesses enough oil for every parish in the diocese for the coming year. The blessed oil is distributed to parishes in small sealed vessels called ampullae or stocks, and a parish priest administers it at baptism, confirmation and ordination but cannot consecrate a fresh batch himself.
Storage and disposal
Chrism is kept in a locked cabinet called an ambry, separate from the plainer oils used for anointing the sick, since only chrism carries the Holy Thursday blessing. When chrism is spilled or a vessel needs cleaning, the cloths and cotton used to wipe up any trace are burned rather than laundered or thrown away, the same rule applied to communion linens that have touched the consecrated host, because a substance this specifically blessed is not treated as ordinary oil once its purpose is served. Leftover chrism from a previous year is typically used up before the new batch arrives rather than discarded early.