Prior to his visits at Auschwitz, Pressac, a French national, was instructed by Faurisson on how to go about conducting his onsite examinations in Oświęcim. He was warned against the tendency to see "falsehoods" everywhere. Instead, he was asked to study and photograph the ruins of crematoria in search of "false interpretations" of visible objects. Upon his arrival in Poland, Pressac believed that he was prepared to "revise" the official history of the camps. Pressac visited Auschwitz Birkenau ten times between 1979 and 1984, according to registered letter from the Auschwitz Museum director Kazimierz Smoleń, sent on 11 September 1985. Pressac used only authentic documents concerning the construction of crematoria and the gas chambers, which originated from the Nazi German office of Zentral Bauleitung der Waffen SS. Museum staff provided him with assistance, convinced of his honourable intentions. Pressac was given access to blueprints which had survived due to being located in the construction office rather than the administrative offices. The analysis of material proof convinced him that his former views shaped by the Faurisson case were in error. He described his experience dramatically in the 'Postface' of Auschwitz: Technique and operation of the gas chambers, saying that he "nearly did away with one evening in October 1979 in the main camp, the Stammlager, overwhelmed by the evidence and by despair". Pressac wrote:
Holocaust publications
Pressac published his conclusions along with much of the underlying evidence in his 1989 book, Auschwitz: Technique and operation of the gas chambers by Beate Klarsfeld Foundation of New-York with translation from the French by Peter Moss. In his 1993 Les Crématoires d'Auschwitz, he further delineated the operation of the crematoria at Auschwitz, and their integration into the larger Nazi program to eradicate the Jews of Europe. Pressac estimated that between 631,000 and 711,000 were killed at Auschwitz.
Criticism
His first 1989 book featuring the totality of Pressac's original research was a soft coverlimited print already translated from French, sponsored financially by the Klarsfeld Foundation. It was a 564-page oblong 'coffee-table' book resembling a profusely illustrated building construction manual. The broader impact of his research was achieved only with the translated version of his second book titled The machinery of mass murder at Auschwitz : design, construction, use, modifications, and destruction of the crematoria and gas chambers which was published in 1993. Reporting from France for The New York Times, Roger Cohen wrote on 28 October 1993: The book written by Pressac was a subject of Ron Rosenbaum's interview with Claude Lanzmann in Paris, conducted for his own book Explaining Hitler. Rosenbaum noted how much the 1985 release of Lanzmann's controversial film Shoah "had raised him to the vatic, prophetic heights" from which he hurled criticism at others. Pressac was no exception. Lanzmann said:
