Single rafter in attic with white substance on all sides.
Not paint - felt “chalky” and did not wipe off by just rubbing. A little saliva and some light rubbing and it did come off.
First thought is it is an old form board, but curious as to why only one, out of all the rafters in the attic.
There were other random framing members painted white also.
I don’t know. That first picture looks a lot like fungal growth. Was it hard and chalky, or was is softer?
Certainly chalky - not wet. Hard or soft is tough ot tell. If you put a gun to my head I’d say it wad hard rather than soft.
If you put a gun to my head, I’d say they were form boards. The second picture sure looks like that. The first one makes me wonder though.
Me too, that’s why I asked.
Thinking I’ll note the condition (unknown substance) mointor and test if desired.
Of course, this one particular board is the third from the end, farthest from the hatch with about 20-24" of clearance below the collar ties. :shock:
Perhaps it was a form board that now has growth!?!?!?
Looks nasty in that attic.
Did they have any venting?
If you put a gun to my head…
I’d have to change my pants!
Looks moldy to me.
Sure you did not steal your picture? :):)
If you put a gun to my head
I would say anything you wanted me too -
Looks like sumatorocrapus. Probably dry but can be activated by small amount of moisture…like saliva. Be careful out there. 
I would vote for mold / fungus.
What I’ve seen in the past, when the boards are used for the forms, the stuff left on the board is rather hard and crusty in places where sometimes the concrete stuck more to the board. Can usually feel the grains of sand and particles.
That is what must happen when the gun is put to your head!:mrgreen:
