Lead-type printing process
The lead-type printing process was a movable type printing process that appeared in Themiclesia around 1300. A hard-metal form was driven into a soft-metal blank to form a type of the desired glyph in negative (the blank areas were higher). Hence, all printed material of the lead-type was "negative", i.e. blank areas were black. It replaced the earlier lead-plate process and was popular for materials with a great quantity of repetitive elements but not others.
The primary genre that saw extensive use of the lead-type printing process were Buddhist sutras, which were transcribed from Maverican with Mengja characters. The practice of transcription was standardized and called for a large quantity of repeated characters, which favoured movable-type priting over relief printing. The genre of official forms also saw printing by lead type, as it too was characterized by a high number of repeated characters.
History
In the 10th century, most printed books produced in Themiclesia were printed by the lead-plate process, a lead plate being the printing medium to which paper was pressed. The lead plate could be either carved or hammered to create illustrations and text; illustrations necessarily were carved, but text could be either hammered or carved. To create a hammered character, a steel type was placed over the lead sheet and hammered, creating a reversed impression of the glyph required. Earlier plates were hand-hammered, but by the 10th century a stable hammering force was achieved by fixing it on an axle; it was then lifted by the operator to a designated height—often by a beam blocking the hammer from going any higher—and then permitted to drop freely. The plate was placed under a grid guide and over a movable so that each impression was evenly spaced and that the hammer did not strike the form at an unintended angle.
Because the form was usually positive, the printing surface and resulting text was negative, i.e. the glyph was left blank, and the empty space around it in ink. Into the 1200s, negative forms were developed, but due to difficulties with controlling the resulting image they were not broadly employed.
Techniques enabling the lead type process existed prior to its emergence. Formerly, if a plate was misstruck, the entire plate might be lost, but around 950, a sharp, heavy die could be used to punch through the lead plate by repeated strikes, leaving a hole. The same die was then used to punch another lead piece whereon the correct strike was made, which would fit neatly into the hole created by the same die; molten lead then filled remaining creveces. This technique came from inserting carved illustration plates, which would be fused to the plate only after the text was struck, since the illustration was far too valuable to be lost for a misstruck glyph. The place where this correction was made is often quite visible, called an erratum (耒, literally "a hoeing", for the process of digging up the error).
In the beginning of the 1300s, larger sets of "errata" were used to add captions onto the blank space on the illustrations, which would be cut out allowing the insertion of the errata. This practice first propagated to any plate where an illustration is to be inserted, and then to all plates whether illustrated or not, by which point the only remaining part of the original lead plate was the bounding frame.
Provenance debate
As both movable-type printing and the first metal types (in bronze) were invented in Menghe, the latter during the 13th century and entering widespread usage, it has been argued that the lead-type process was a hybrid process that borrowed elements from the bronze type found contemporarily in Menghe.
Against this argument, it has been noted that the first "movable" erratum was found as early as the middle of the 10th century, well outdating the initial introduction of movable type in Menghe, and the process for creating the lead types were very different from those in common use in Menghe. On the other hand, errata were strictly employed for the correction of errors until 1300, the publication year of the earliest surviving book with intentionally-punched holes for the insertion of text in illustration, and the broad application of errata on other plates does not occur until the end of the century, when bronze type printing was widely employed in Menghe. Facts such as typesetting sequence, backing material, and binding practice have been cited in favour and against Menghean influence as early as 1902.
It is widely accepted that many Themiclesian printers travelled to Menghe during and after the 14th century when a prolonged peace, known as the Pax Mengeana, existed in East and Central Hemithea. As books were published at an unprecedented rate during the Menghean golden age, Themiclesian printers often searched for new titles not yet available in Themiclesia to be re-printed domestically. Thus, "it is difficult to rule out the possibility that some Themiclesian printers learned of the Menghean technology and sought to replicate it in spirit by existing, domestic means." The debate is also complicated by poorly-documented technicalities and working preferences in which Themiclesian printers differed from each other, e.g. some printers never use errata on illustrations at all.