[Hox501s]

Hello, first post here.

I want to do a particular experiment with my high school 1st year Chemistry class that I did quite some time ago when I was in school. As I recall, I used lycopodium powder dusted over a shallow pan of water. I dropped oleic acid and used the radius of the resulting oil spill to calculate an approximate atomic radius (Equivalent volumes and whatnot.)

My question is this; in trying to replicate that experiment with the materials on hand, I can't seem to figure out why some oils spread easily on the surface of the water while others do not. I've used standard vegetable oil, various olive oils, and mineral oil to name a few. Any ideas for why some oils spread quickly and thinly (allowing the assumption of the 1 molecule thickness of the oil layer,) where others stay pooled?