Derek Cohen (in Perth, Australia)
What I do notice is this:

We all recall the heat that occurs when using a cabinet (card) scraper - the burned thumb experience? I suspect that high cutting angles are more likely to produce heat in plane blades.

I have observed for many years that a plane that always requires the back of the blade being cleaned is the HNT Gordon smoother (60 degree bed angle, used with a 1/4" thick and 2" wide O1 blade). What occurs is that the back of the blade becomes brown with a resinous coating. Where does this come from? Springback? What these blades in particular? Is this linked to the wood type?

The "resin" has to be scrubbed off before lapping the back of the blade. It will gum up media if this is not first done.

Regards from Perth

Derek