A Hillhouse student’s eyes widened as he applied grape juice and heat to what appeared to be a blank piece of paper — but instead held a secret message in invisible ink, written as part of a course ...

Have you ever wanted to send a secret message to a friend that no one else can read? Invisible inks can help you do that! When you use an invisible ink to write a message, it quickly disappears. The ...

Click to share on Facebook (Opens in new window) Facebook Click to share on X (Opens in new window) X Hillhouse students at work writing invisible ink messages ...