John Trapp on Job 41:31

Verſe 31.Plin. lib. 9. c. 3. & 6. He maketh the deep to boyl like a pot] He troubleth the whole Ocean: he maketh a mighty commotion in the ſea, when he rouls himſelf therein upward and downward, and caſts up water on high thorow a certain conveyance, that he hath in his head.

He maketh the ſea like a pot of oyntment] Turning it into a foam, like the ſcum of a boyling pot. Beza rendreth it thus, He maketh the ſea like a Mortar, wherein colours are beaten: that is, the whirling of the water is like unto a quern that is turned round of the painter, to temper his colours.