![HB Dobbie’s blue fern albums](http://static.sciencelearn.org.nz/images/images/000/001/236/full/HB-Dobbie-s-blue-fern-albums20160620-8847-16ah4um.jpg?1674165741)
These books have full-sized, white silhouettes of ferns on a blue background and are known as the ‘blue books’. They are made using an early form of photography called the cyanotype process.
These books have full-sized, white silhouettes of ferns on a blue background and are known as the ‘blue books’. They are made using an early form of photography called the cyanotype process.