I think foundation would be too easily confused with foundation that is used on the face.

Clinique Lash Building Primer + Clinique Lash Doubling Mascara, 01 ...
Clinique Lash-Building Primer: Lash-conditioning **undercoat** boosts the benefits of Clinique mascaras. Unique polymer combination holds mascara to lashes for ...
shopwiki.com/detail/d=lash_building_primerlash_doubling_mascara,_01_black/jumpToFirst=true/

Jack & Hill: A Beauty Blog - make-up, cosmetics, perfume, and the ...
Guest contributor Helena Handbasket continues her series: The Mascara Trials of ..... XXL Mascara that includes a white, microfiber **undercoat** and black, ...
jackandhill.typepad.com/jack_and_hill_a_beauty_bl/mascara/index.html

Mascara
Clear Mascara - why?? at Beaut.ie - The Irish Beauty Blog ...
Another useful application is as an **undercoat** before your regular mascara. A couple of coats of clear mascara will build up and give body to your lashes. ...
beaut.ie/blog/?p=159

Mascara -- 15 Mascara Tricks & Tips
Tip #11: Use a **mascara primer**. Primers coat lashes and separate them before you apply mascara. Makeup artists swear by mascara primer. ...
beauty.about.com/od/mascara/a/mascara.htm

I am Fashion: Beauty Trend FW05 I: The essentials
Use an eye-curler (like this Shu Uemura one) to curl the lashes, and swipe on a layer of **mascara primer**. (I like the Lancome Cils Booster. ...
iamfashion.blogspot.com/2005/09/beauty-trend-fw05-i-essentials.html