Line your work surface with newspaper to help protect it. Lay your item that you desire to crackle on top.
Brush a layer of paint onto the item that you desire to crackle. The color of this base coat of paint will become the cracks showing through the surface of the top coat of paint. Allow the paint to dry before continuing.
Pour some of your hide glue into a disposable bowl. If small cracks are desired in the finished piece, add a small amount of water to the glue. If large cracks are desired, do not add water. Stir the glue and water with a paint stirrer.
Brush the hide glue mixture onto the painted item with a paintbrush. Allow the glue to dry for 24 hours before continuing.
Paint the contrasting shade of paint over the top of the hide glue, making sure not to overlap strokes. Work as quickly as possible in order to achieve the most natural crackle effects. The paint will shrink over the hide glue as it dries, revealing cracks in the surface.