Today I was using a Feather blade for the third time (in a new Feather AS razor). I tried a new shaving soap, and was surprised that the blade felt repetitively dull from the get go, and seemed to get worse. I normally get 4 or 5 good shaves out of a Feather in my various Merkur razors, so I'm trying to figure out whether it is the different soap, or the Feather AS razor that caused the apparently short blade life. I bowl lather but work it in on my face pretty well. I do a 3 pass shave.
What (if any) soap characteristics might tend to make a blade feel dull sooner than normal?
What (if any) soap characteristics might tend to make a blade feel dull sooner than normal?