Gypcrust is like a really hard fairy bread that you make on walls and ceilings!
When people build houses, they often use a special powder called gypsum to make walls and ceilings. To make gypcrust, you mix gypsum powder with water until it becomes like a thick paste.
Then, you spread this paste over the surface you want to cover, like a cake. You can use a special flat tool called a trowel to help you spread it out smoothly.
Once you've spread the gypcrust over the surface, you can decorate it with pretty patterns or leave it plain. It dries really hard, like a cookie, and becomes part of the wall or ceiling that it's on.
Gypcrust is often used to decorate fancy buildings or historic homes. It lasts a really long time and helps to protect the walls and ceilings from damage.