Clearing the "old" scrollback buffer

Clearing the "old" scrollback buffer

This might seem to be a duplicate question but it isn't.
I know that I can use printf "\033f" to clear the scrollback buffer of the
"current" session but that doesn't work for old sessions.
My problem is I access several VM's through XVP viewer (a java web browser
based VNC) and if I don't make a effort to clear the screen before logging
out every time everything can be viewed by scrolling the screen.
Please suggest a way to clear this old scrollback buffer.
PS: Rebooting clears it but I can't do that on production VMs