In 1764 he brought forth that synthesis of the resources of his art which was to shake the Ukioye world. Whether he was the actual inventor of polychrome printing is not certain; some authorities attribute the invention to an engraver named Kinroku; but it is very clear that Harunobu was the first to seize upon and realize the possibilities of the discovery. Some technical hindrance, such as the difficulty of securing perfect register from many blocks on the wet stretching sheets, had prevented the earlier completion of the process; and it is possible that it was a printer who discovered the simple device needed to overcome the difficulty. This, however, is a matter of mere mechanics and has no bearing upon the question of the real glory of Harunobu. What is important is that he seized the new technique and made out of it an instrument responsive to every subtlest breath of his beauty-haunted spirit.
[Illustration: HARUNOBU: LADY TALKING WITH FAN-VENDOR.
Polychrome. Size 11 × 7½. Signed _Harunobu ga_. Chandler Collection.
The old three-colour prints had achieved fine effects by means of powerfully conceived but essentially simple mosaics of colour. Now Harunobu turned the three-stringed lute into the violin, capable of expressing the most delicate modulations of tone. Beginning with combinations of only four or five colours, he gradually increased the number of blocks used. It is certain that he used eight blocks on at least one 1765 calendar print. In the end he had at his command a palette which, by the use of no less than twelve or fifteen blocks, and with the limitless number of shades obtainable by superimposing one colour upon another, made the whole rainbow his. Constant experiment marked his further progress. We have, for example, one print which he originally printed from eight blocks, and later varied by increasing the blocks to ten, and still later to thirteen. From year to year an ever fresh succession of complex colour-harmonies emanated from his fertile brain.
Until the invention of polychrome printing, Harunobu had not adequately expressed himself; now, having found his true instrument, he played divinely. The year 1765 was a Jubilee year, celebrating the nine-hundredth anniversary of the entrance of Sugawara Michigane, the great statesman, painter, and humanist, to the Court of the Emperor. This circumstance, in connection with the desire of literary men to present to their friends specimens of the new prints as New Year cards, led Harunobu to produce a number of dated calendar-prints of this year--a fortunate occurrence which has been of great aid to students of his work. The theory that these dated prints are the expression of Harunobu's naïve exultation over the new discovery is now generally discredited. Since the calendars are dated 1765, Mr. Gookin's suggestion that they were probably made in the last months of 1764 seems reasonable; and this date must therefore be regarded as marking the beginning of polychrome printing.