That knowledge of the hieroglyphic system and the principles upon which it was devised had not become diluted with time is attested by two phenomena: cryptography and the development of the hieroglyphic writing during the last millennium of its existence. From the middle of the 3rd millennium but more frequently in the New Kingdom (from c. 1539 to c. 1075 bce), hieroglyphic texts are encountered that have a very strange appearance. The absence of familiar word groups and the presence of many signs not found in the canon characterize these texts at first glance as cryptographic, or encoded, writing. This kind of hieroglyphic writing was probably intended as an eye-catcher, to entice people to seek the pleasure of deciphering it. Composed according to the original principles of the script, these inscriptions differed only in that certain features excluded when the original canon was formulated were now exploited. The new possibilities involved not only the forms of the signs but also their selection. For example, the mouth was not drawn in front view (), as in the classical script, but in profile (), although it had the same phonetic value. An example of a change in the choice of signs is the case in which a man carrying a basket on his head (), a determinative without phonetic value in the classical script, was later to be read as f and was used in lieu of the familiar sign having this phonetic value, that of the horned viper. In the new selection of the sign, the phonetic value is obtained from the word f + š + ỉ “to carry” (neglecting its two weak consonants), in accordance with a principle that the inventors of the writing had applied in 3000 bce. These cryptographic inscriptions prove that alongside the method of instruction in the schools, which was based on memorization or recognition, not upon analytical understanding, there was another tradition that transmitted knowledge of the basic principles of the hieroglyphic script. A command of the principles of hieroglyphics similar to that which the composers of the cryptic inscriptions had was presupposed for the puzzle-happy decipherers.

The later development of hieroglyphic writing

About the middle of the 1st millennium bce, Egyptian writing experienced new developments and a revival of interest. Again the inscriptions abounded with new signs and sign groups unknown in the classical period, all generated according to the same principles as the classical Egyptian script and the cryptographic texts. The writing of this late period was distinguished from the cryptograms in that this script, like every normal system of writing, developed a fixed tradition, being intended not to conceal but to be read easily, whereas the cryptography strove for originality.

The development of hieroglyphic writing thus proceeded approximately as follows: at first only the absolutely necessary symbols were invented, without a canonization of their artistic form. In a second stage, easier readability (i.e., increased rapidity of reading) was achieved by increasing the number of signs (thereby eliminating some doubts) and by employing determinatives. Finally, after the second stage had endured, essentially unaltered, for about 2,000 years, the number of symbols increased to several thousand about 500 bce. This rampant growth process occurred through the application of hitherto unused possibilities of the system. With the triumph of Christianity, the knowledge of hieroglyphic writing was extinguished along with the ancient Egyptian religion.

Tools

The tools used by the craftsmen for writing hieroglyphic symbols consisted of chisels and hammers for stone inscriptions and brushes and colours for wood and other smooth surfaces. A modified form of hieroglyphic writing (called cursive hieroglyphs), in which certain details of the monumental signs were abbreviated, was used for the decorative and minor arts—that is, for inscriptions chased into metals, incised in wood, or lavishly painted onto papyrus. Only for the truly cursive scripts, hieratic and demotic, were special materials developed. Leather and papyrus became writing surfaces, and the stems of rushes in lengths of 6 to 13 inches (15 to 33 cm), cut obliquely at the writing end and chewed to separate the fibres into a brushlike tip, functioned as writing implements. The split calamus reed used as a writing implement was introduced into Egypt by the Greeks in the 3rd century bce.