White VS Black Grease Clogs

[10" pipe]

Does anybody know why some grease clogs are white and chalky while others are black and creamy? Been running into a lot of each lately and can't figure out why the difference.

 

[Terry]

I don't do much snaking. I heard my sister-in-law mention the other day that she always poured grease down her kitchen sink. I almost fell over when I heard that. She was at my mothers, and that would be a mess if someone started doing that to her 250 foot sewer line.

Kitchen lines that were cut out, filled with grease.