temper

To modify by the addition of a moderating element; moderate: synonym: moderate.

To bring to a desired consistency, texture, hardness, or other physical condition by blending, admixing, or kneading.

To harden or strengthen (metal or glass) by application of heat or by heating and cooling.

To strengthen through experience or hardship; toughen.

To adjust (the pitch of an instrument) to a temperament.