Like a face primer, an eyeshadow primer works in a similar fashion. Mostly, it 'holds' the powder that usually flies off one's face as the day progresses. Think of it like 'sticky glue' that will stick your eyeshadow to your lid until you're ready to call it a night. I use primer everyday, whether I'm toning it down for work, making it sassy for a girl's night out or chaneling TayMom's rocker girl look for a great party.
Want proof? Observe:
I have an olive pigmentation so of course the colors look different on everyone. The samples on the left are the ones using a primer and 2 brush strokes. The ones on the right are no primer and also 2 brushstrokes. I'd also like to say that while doing this post and moving about the one on the right is nearly gone while the sample on the left is still there waiting for me to clean it off. The lesson? Use primer.
I've personally used the Too Faced one & the Mary Kay but here are some good ones that I've heard of people recommending:
(great if you have sensitive skin)
MAC's Prep & Prime $16.50
Let me know if you know of any other good ones I love to try new stuff!
ETA: I had one of you email me and tell me that if you use regular face primer it will do the same thing and you're right! I tried it on an eyeshadow I never use because as you can see without primer it's quite a dissaster. I used my regular Smashbox primer and voila! I think this one is going out tomorrow night with me when I meet my friend at Season's 52.