Anton Raphael Mengs (1728-1779), though born in the Kingdom of Bohemia, resided much of his life in Rome. At the point where Casanova visited him in Rome, Mengs lived at Via Vittoria 54, not far from the Spanish Steps. J. Rives Childs also tells us that Francesco de Rossi ran the boardinghouse (p. 140). At this point, Mengs had been a successful painter for years and had also taken as his pupil Giovanni Casanova, Giacomo’s younger brother. When Casanova had visited Madrid in 1768, he was accused of illegally possessing a weapon; he hid at Mengs’ house before being arrested on February 20 and imprisoned for two days at Buen Retiro.
Giacomo was extremely reluctant to visit Mengs while in Rome because his brother Giovanni was in disrepute at this time. Added to that, when they had all met in Madrid, Casanova felt that he had been ill-treated by Mengs and he held a grudge. But Mengs, seeing Casanova at a painting prize ceremony, approached him and offered this explanation: “If you had known Madrid as I do,” Mengs said, “and the necessity I was under to give no opening to evil tongues, you would not have forced me to do what I did. Learn that I was believed to be a Protestant, and that to add color to the suspicion I had only to show myself unconcerned by your behavior.”
Mengs invited Casanova here, to Via Vittoria 54, for dinner “under the auspices of Bacchus” to clear the air. Mengs also assured Casanova that his brother Giovanni would not be present.
You see, Giovanni had fraudulently tried to pass off a couple of his own paintings as antiquities in 1761 to the renown painter Johann Winckelmann, also a friend of Mengs. When the fraud was discovered, Winckelmann sued Giovanni Casanova in absentia; however, Giovanni did visit Rome in 1771, but his brother Giacomo wanted nothing to do with him, afraid to tarnish his own reputation. Over dinner and wine, Mengs and Casanova were able to repair any past harms and appeared to make amends.
There seems to be a discrepancy about C’s dates for visiting Mengs in Rome. Casanova writes about this visit in Vol. 12, Ch. I, which would be 1770. But Willard Trask notes that Mengs did not come to Rome from Madrid until February of 1771, so C must have seen him at that time, after Casanova had visited Naples and then returned to Rome. (See Trask’s note 17, Vol 11, Ch. IX.)
(Some info from J. Rives Childs. Casanova: A New Perspective. Paragon House Pubishers, 1988.)