  Graph-bootstrap percolation, also known as weak saturation, was introduced by
Bollob\'as in 1968. In this process, we start with initial "infected" set of
edges $E_0$, and we infect new edges according to a predetermined rule. Given a
graph $H$ and a set of previously infected edges $E_t\subseteq E(K_n)$, we
infect a non-infected edge $e$ if it completes a new copy of $H$ in
$G=([n],E_t\cup e)$. A question raised by Bollob\'as asks for the maximum time
the process can run before it stabilizes. Bollob\'as, Przykucki, Riordan, and
Sahasrabudhe considered this problem for the most natural case where $H=K_r$.
They answered the question for $r\leq 4$ and gave a non-trivial lower bound for
every $r\geq 5$. They also conjectured that the maximal running time is
$o(n^2)$ for every integer $r$. In this paper we disprove their conjecture for
every $r\geq 6$ and we give a better lower bound for the case $r=5$; in the
proof we use the Behrend construction.
