How to remove blur on hover

I've figured out how to add blur to images with: filter: blur(8px); But I don't understand where to put the custom css to unblur the image on hover. When I add this to the styles for an image block, nothing happens.  Help? -webkit-transition: 1s -webkit-filter linear; -moz-transition: 1s -moz-filter linear; -moz-transition: 1s filter linear; -ms-transition: 1s -ms-filter linear;