On May 7, 1840, Dr. Pignier was forced to retire from the position of director of the Institute and was succeeded by his former assistant, Pierre-Armand Dufau. Dufau did not approve of Louis Braille's code and banned its use by students and teachers at the Institute. It is said he did not like Louis' code because he was afraid that there would be no need for sighted teachers if everyone who was blind could read as a result of using braille.
In April 1843, Louis was forced by ill-health to convalesce for six months in Coupvray. When he returned to Paris he discovered that Dufau had burned 73 books produced by Guillié and Pignier using Haüy's embossing method. The director thought a different embossing system, in use in the United States and Scotland, was superior to Haüy's system. The method was called Boston Line Type, and eventually it was found to be less effective than Louis Braille's code.