In 1780 four rival pottery works were established in the neighbourhood which copied and imitated the pottery made at Alcora. The two most important were at Rivasalbes and Onda, the other two at Alcora itself. Many of the artists who belonged to the works established by Count Aranda worked at the rival factories; among them were Mariano Causada, Joaquin Ten, Francisco Marsal, Vicente Alvaro, Christoval Mascarós, Francisco and Miguel Badenas, and Nadal Nebot; some of these artists returned to the Count's manufactory. In order to distinguish the genuine pottery from imitations, orders were given, with the authorization of the Tribunal of Commerce, that the pottery made there should be marked henceforward with the letter A; no special mark had hitherto been used at the manufactory, the artists very often signed the specimens they made with their monograms or signatures, of which those most frequently met with will be found accompanying the list of artists' names, for the help of collectors; all of them have been copied from original documents. It is interesting for collectors to bear in mind, that all specimens which are marked with the letter A are _posterior_ to 1784. The pottery works founded in imitation of the manufactory belonging to Count Aranda came to an end before 1790, some by special agreement with the owners themselves, and others by the express orders of the authorities, in virtue of the privileges granted to the Count. Mr. Martin died at Alcora in the month of May, 1786. Knipfer left soon afterwards, and was succeeded by a French artist, M. Pierre Cloostermans, a skilful man, and well versed in the manufacture of porcelain pastes, as well as in painting and decorating them. According to his contract, which was drawn up in Paris in 1787, "Pierre Cloostermans, chemiste, natif de Paris, demeurant à Paris, Rue de Clery, au coin de celle Montmartre," agreed to "live for thirty years at Alcora as director and workman, to make soft and hard porcelains, and all the necessary colours with which to paint and decorate it."