Assertion: flat surface | /r/HasProperty | refined to precise flatness
Facets:
value: by rubbing them
type: MANNER
value: progressively
type: MANNER
value: in this process
type: TEMPORAL
Source sentences:
text: In this process, three approximately flat surfaces are progressively refined to precise flatness by manually rubbing them against each other in pairs with colouring matter in between, and then hand-scraping the high points.