You and Kris toughened me up.
Hell toughened him up, yet this was one challenge he couldn.t figure out.
Being very brittle, the spar is rather difficult to work on the lathe, and is often toughened by means of resin.
From the nitrate are made (a) argenti nitras indurata, toughened caustic, containing 19 parts of silver nitrate and one of potassium nitrate fused together into cylindrical rods; (b) Argenti nitras mitigatus, mitigated caustic, in which 1 part of silver nitrate and 2 parts of potassium nitrate are fused together into rods or cones.
Generally towards the end of the first year the original thin protective layer of a stem or branch is replaced by a thin layer of "cork," that is a layer of cells the living contents of which have disappeared while the walls have become thickened and toughened as the result of the formation in them of a substance known as suberin.