How many projects are needed to go up to the ‘scratcher’ level?

We have a quite useful topic about this here. The short of it is there's no set amount of projects that will make you a Scratcher.

jvvg wrote:

Just be active, post constructive comments on peoples' projects, make projects, and generally be helpful around the site, and you will eventually find a link on your profile that says “Become a Scratcher”. Click it, and you will be promoted.

Hope that helps!