coarsen

coars|en /k'ɔː^rs^ən/ (coarsens coarsening coarsened)
1 [VERB] V, V-ed, also V n
If something coarsens or is coarsened, it becomes thicker or rougher in texture.
Skin thickens, dries and coarsens after sun exposure.
...his gnarled, coarsened features.
2 [VERB] V, V n
If someone's behaviour or speech coarsens or if they coarsen it, they become less polite or they begin to speak in a less pleasant way.
Her voice has deepened and coarsened with the years...
He had coarsened his voice to an approximation of Cockney.