Now, I very rarely say with any seriousness that a product is needed or necessary - but I'm about to, because if you ever wear eyeshadow you NEED Darling Girl 'Glitter Glue'. Glitter Glue takes eyeshadow from 0 to 100 in 1 second, making it look far more incredible than you could have ever guessed it was. You might as well just stop reading now, go buy it, then gush about it to me later on Twitter. Maybe I should indulge you to an actual review and some pictures first, though? Oh, go on then...
Before anything, lets have a chat about the difference between primers and bases. Primers make things stay put and bases make things look bolder, for maximum effect a primer followed by a base will never do you wrong. I've been using Darling Girl 'Glitter Glue' as my base since it was first released (a couple years ago?!) and haven't looked back since.
Glitter glue has the appearance of PVA glue and a similar texture, which might sound pretty unappealing! Fear not, it's 100% eye safe, wont glue your lids together and wont peel off like sheets of snake skin (don't pretend you never 'accidentally' spilt glue on yourself at school...) I use a teeny tiny amount and apply it to my lid with my fingers; it becomes clear and leaves a tacky base for your eyeshadow.
The above swatches show eyeshadow straight over primer, then over primer and glitter glue (with hearts.) I'm pretty sure you can tell the difference! 'Glitter Glue' grasps to glitter and shimmer, keeping it firmly in place - meaning your eyeshadow never goes from 'BOOM!' to 'blah' through the day. I've also found that 'Glitter Glue' makes the colour switch in duochromes more evident, which is only ever a good thing!