Because its by the door Andy and and because of weather conditions and wind it got walked on plaster trodden it to it.Why are you asking? Seems strange that OSB would need to be spot (stain) less, and if it did, why wasn't it covered before you plastered?
What so OSB is being used as a finished floor? That's got to be a first? Could possibly look effective if treated right.Because its by the door Andy and and because of weather conditions and wind it got walked on plaster trodden it to it.
Because its not a house/home. its only the mrs studio and storage and will get minimum traffic from her hooves.
In total it is 700sq ft. it would cost a fortune to cover it with a floor of some kind.
Or turn the osb board over so clean side is showingShould scrub clean. Worst case, just replace the osb.