[header] How to clarify stock [title] Allow your stock to simmer until the soup's fat floats to the surface. [step] As you let your stock simmer, the fat will rise to the top creating a foamy buildup. [substeps] If there is an excess of foam or fat buildup, it's possible that you have your heat turned too high. 
Stock needs to be slowly simmered over a long period of time, not boiled. Typical stocks should be simmered anywhere from 4 to 6 hours long.