Syntax for using 'not'? I want to show a list of entries that excludes two or more specifically by id.

This works:

{% for entry in craft.entries.section('boardOfDirectors').id('not 12') %}


This does not:

{% for entry in craft.entries.section('boardOfDirectors').id('not 12,18') %}


Is this possible?
Anyone know the correct syntax?
You need to start with and, and put not in front of each ID...

{% for entry in craft.entries.section('boardOfDirectors').id('and, not 12, not 18') %}