glassen vs scumble

glassen

verb
  • To coat or cover (e.g. pottery, etc.) with glaze; make glassy. 

adj
  • Resembling glass; glassy; glazed. 

  • Made of or consisting of glass. 

scumble

verb
  • To apply an opaque glaze to an area of a painting to make it softer or duller. 

noun
  • An opaque kind of glaze (layer of paint). 

How often have the words glassen and scumble occurred in a corpus of books? (source: Google Ngram Viewer )