When a dispersion of stable colloidal particles is dried the particles pack and form a solid network. If the particles are weak enough they deform and a continuous film, with a particle volume fraction of unity is formed. For polymeric particles, interdiffusion of polymer chains blurs out the existence of the original particles and a continuous polymer film is created. This process is called film formation.
For harder particles, the film is weak and cracks upon drying to relieve stress. The crack pattern and spacing has been the subject of much work and we have shown how flow of solvent away from defects in the film set the spacing and lead to a stick-slip motion of the crack through the drying film.