This is a common problem many new artist to Blender might come across. You spend a lit of time creating your materials assign them and create new ones and reassign them. You would think by saving your file would store all those materials one file. However opening up the file again you notice your material list have shrunk. This is because Blender does not save materials that are not assign to an object. I learnt hard way myself. To over come this problem next time you can select the material and click on the shield icon. This will put an F next to the shader sphere. Repeat any materials you wish to protect and [...]