Luminous Chalk

Luminous Chalk is the collective designation for a family of self-emitting marking compounds held in the Tower's stores and issued under grade to the various bodies that require a mark capable of being read without a lamp. It is distinct from Memoria Chalk, which emits nothing, and from Void-Chalk, which absorbs what is directed at it. The grades run from A to E in descending order of output; only Grade B and Grade D are in general circulation. Grades A and C are reserved to the Office of Luminous Accounting and are not to be requested by the unaided petitioner, though the reason for the reservation has not been restated since the original instrument and is presumed to be sound.

Grades and issuance

Grade B, the ordinary working chalk, is certified by the Directorate of Luminance on Floor 8 and issued in sealed boxes of forty-eight sticks. It burns with a steady, low, greenish-white light for a stated eleven hours and is inert thereafter. Luminous Chalk is used by Wayfinders for temporary sigil-marking on non-material surfaces, being non-luminous only when spent and therefore incapable of interfering with a subsequent annotation. The residue should be brushed away before a volume is re-shelved. This instruction is printed on the lid, and has been printed on the lid since the fourth recension.

Grade D is weaker, warmer in colour, and issued to those working in the sub-vaults where a brighter mark would throw a shadow and be mistaken for a second object. Grade E is not chalk in any meaningful sense and is issued only to the College of Luminous Anomalies for comparison.

Conduct and interference

The compound's defining property is its activity. A mark laid in Grade B continues to emit until its charge is spent, and while emitting it is not merely visible but present in a way that the Treatise on Luminous Quarantine describes as "admitted to the room." Ordinary inks do not do this. It is therefore required that no active luminous mark be laid over, under, or across any Memoria inscription, since the two compounds interact and the interaction is not one the Tower has elected to supervise.

"A luminous mark is a mark that insists. The archivist who lays one must be prepared for the page to answer."

— Treatise on Luminous Quarantine, Section 9

The precise mechanism was set down after the Crisis of Recursive Annotations on Floor 719, in which an archivist correcting a Memoria annotation with Grade B produced a Protocol-Bound Annotation neither he nor the floor could subsequently remove. The Third Concordance treats the incident as a caution; the Seventh Concordance, drafted eleven years later by clerks who had not been present, treats it as a demonstration and cites the resulting annotation as evidence that the two media are "complementary rather than adverse." Both instruments remain in force.

Relation to other media

Grade B is frequently specified alongside Luminous Mortar in structural work and alongside Luminous Verdian in the marking of cultivated beds. The Office of Luminous Accounting maintains that all three share a common charge and differ only in binder, and has petitioned three times to have them entered under a single heading. The petition has been refused three times, on each occasion by a different committee and for a different reason. The Luminous Signature — the characteristic fade-pattern by which a spent mark can be identified to its grade — is registered for chalk, mortar and verdian separately, which the Office regards as redundant and the Registrars regard as the point.

Confusion with living specimens is common and should be resisted. Luminous Moss, Luminous Lichen and the Luminous Lichen Archival Specimen all emit, but they grow, and a mark that grows is a different category of problem. Luminous Moss in its general sense is treated at its own holding.

The winter requisition of Floor 331

In the winter of the year recorded as 331-C, the sub-librarian in charge of that floor's east gallery submitted a requisition for two hundred boxes of Grade B against a projected need of nine. The discrepancy was traced to a clerk, one Ostrev Halden, who had been instructed to count the gallery's unlit alcoves and had counted them once for each hour of his shift, producing a figure he defended as "thorough." The Office of Luminous Accounting declined to withdraw the boxes once issued. Floor 331 remained the brightest floor in its spiral for the better part of a season, and the resulting glare is still cited in the Eleventh Concordance as grounds for the rule that requisitions be countersigned by a second clerk who has actually been to the floor in question. Halden was reassigned to inventory and is remembered chiefly for the note he appended to his own file, which reads in full: "The alcoves were there. I did not invent them."

Storage and prohibition

Luminous chalk is stored in the dark, in sealed boxes, in a cool and dry recess of the Chalk Vault on Floor 1024 set aside for reactive materials. It must not be stored in the same recess as Memoria Chalk, a separation the Vault's custodians enforce without exception and without explaining, the Adjudication of the Chalk-Dust Hands having settled the matter in a manner the custodians regard as conclusive and the Office of Luminous Accounting regards as merely emphatic.

Boxes are not to be opened to check whether the chalk still glows. Opening a box admits the charge to the room and spends it; a box opened for inspection is a box consumed. This has been the rule since the first recension and has been broken in every year since, generally by clerks newly assigned and anxious to be seen to be diligent. The Office of Luminous Accounting records each such breach in a ledger kept for the purpose and takes no further action, the ledger itself being considered the remedy. Wayfinders drawing Grade B for a descent are reminded that the chalk is issued for the marking of surfaces, not the lighting of passages, and that a stick so used is to be surrendered on return and entered as spent, whether or not it is.

Records

The fullest account of the grades and their conduct remains the Luminous Signature register, which lists the fade-pattern of every certified stick by batch. Readers wishing to pursue the interaction of active and inert media should begin with Memoria Chalk and the Protocol-Bound Annotation, and should note that the Third Concordance and the Seventh Concordance do not agree on what occurred on Floor 719. The archive takes no position. The archive has two positions, filed adjacently.