Apartment Therapy has a thread on how to frost glass temporarily when you are renting. Readers from years back might remember I had a page about using squares of clear contact paper to create this effect. However, the third place I used this in the contact paper didn’t pull off cleanly, much to my dismay. The adhesive was left stuck to the window and I spent an entire day with plastic scrapers and various Goo Gone products getting it off.
The thread has some first hand experience from people who have applied the frosting film you can find at home improvement stores, or used glass frosting sprays. I’m also going to point out Ikea’s Amorf Frost, someone wrote to tell me this is applied with a little bit of soapy water.