quadratics and lighting

for some reason sometimes when i make a quadratic-- not always, apparently-- the world’s lighting is brightened. i have no idea how this could happen, does anyone else?

This could be related to something like missed call to

glEnable(GL_NORMALIZE).

If GL_NORMALIZE enabled, normal vectors specified with glNormal are scaled to unit length after transformation. It is disabled by default (as I recall). And non-unit-length normals cause intresting (and strange) effects on lighting.

Yuri