In both, the focal images were done by stamping with bleach. What is most interesting about this technique is that you really never know exactly what the bleached out image is going to look like in advance. Different colored cardstocks react differently to the bleach. And you may not even get the same result each time you use the same cardstock.
If you look at the card directly above, you can see that even within the one stamp, the flowers are not uniformly bleached out. And I love that!
How to do it? Couldn't be easier. Just make a stamp pad by putting a couple of layers of paper toweling in a shallow container and wet them down with the bleach. Press your stamp into the pad and then onto your paper. Silhouette stamps work particularly well with this technique, but try a variety of stamps on different papers and see the results. How much bleach you use and how hard you press will also affect the outcome. Have some fun and experiement!
Just remember to clean your stamps afterwards. And work in a well ventilated room!