The 10th of Av is also considered a solemn day, as the Temple still burned on this day. The Temple was only set alight at the end of the ninth and burned through the tenth. Jews refrain from eating meat during the "Nine Days", but also on the tenth.
From the 10th of Av onwards we will start seeing a turn in negative energy. It will dissipate by the time we reach the 15th of Av, (Tu B'Av) an ancient Biblical festival that carries tremendous light. More on that soon...