The first picture shows the material in an untreated condition, whereas in the second picture the material was treated with a nylon-diamond internal brush (Grit 400, diameter 10 mm, min-1 1.500, clockwise and counterclockwise rotation for 5 sec.).

Likewise, the first picture shows the material in an untreated condition. On the following picture, the material was treated with a microabrasive tube brush (aluminium oxide, Grit 600, diameter 8,2 mm). On the third picture you can see the working results after the use of a nylon-diamond internal brush (Grit 400, diameter 8,0 mm).