This video is courtesy of Ceramic Arts Daily. Potters Don Ellis and Randy Brodnax demonstrate how to create a crackled texture on a wheel thrown piece.
http://ceramicartsdaily.org/pottery-making-techniques/ceramic-decorating-techniques/pottery-decorating-video-what-a-stretch-how-to-use-sodium-silicate-to-create-crackled-texture-on-pottery-surfaces/