rehardenv.

1605 J. Sylvester tr. G. de S. Du Bartas I. Posthumus Bartas 71 in Deuine Weekes & Wks. (new ed.) The Kings [sc. Pharaoh's] repentance endeth with his paine. He is re-hardned [Fr. il s'endurcit].

1678 J. Moxon Mech. Exercises I. i. 11 You must..harden the point of it..because the heat of the Iron will soften it fast enough,..but then you must re-harden it.

1678 T. Hobbes Decameron Physiologicum vii. 75 I conceive now how a Body which having [sic] been Hard and softened again, may be rehardned.

1771 W. Newton tr. Vitruvius Archit. i. iv. 11 When it is thus soft and burning hot, if it is cooled again by being steeped in water, it is rehardened and restored to its former strength.

1843 C. Holtzapffel Turning & Mech. Manip. I. 246 The knife edges..being found too soft..were re-hardened.

1874 T. Davies Prepar. & Mounting of Microsc. Objects (ed. 2) 160 If curved by heating and bending to any required shape they may be re-hardened by putting them whilst hot into cold water.

1912 Times 20 Apr. 12/5 Apart from the fact that the excess lime re-hardens the water, it is not desirable to give the consumer lime-water to drink.

1967 Speculum 42 322 They are much less brittle than solid carbon steel, and more easily re-cut and re-hardened if they become dull.

2006 Olive Oct. 88 (advt.) Sensodyne Pronamel is an everyday toothpaste specifically designed to help re-harden your tooth's softened enamel.

1829 J. L. Knapp Jrnl. Naturalist 7 That lime rehardens after being made soft, as in mortar, is owing to [etc.].

1880 Harper's Mag. Nov. 904/2 This firing being of sufficient intensity to soften the glaze already on the article, thus allowing the colors to sink into it, and when it rehardens, renders them durable and impervious to most outside accidents.

1928 Philos. Rev. 37 611 Even when morality is most intelligent and hence most adaptable, it continually rehardens into set formulæ.

1960 Jefferson City (Missouri) Post-Tribune 28 Jan. 13/1 We returned the layer of chocolate left, after the hearts were cut out, to the refrigerator to re-harden.

2006 R. P. Gates Grimm Reapings v. 257 The reflection melts and rehardens into the fictitious face of the handsome Trevor Flint, Pioneer.

1675 A. Woodhead et al. Paraphr. St. Paul 35 That re-hardening still of Pharaoh's heart.

1854 De Bow's Rev. Nov. 488 The operation of softening and re-hardening deteriorates the quality of the steel.

1989 Biotechnol. & Appl. Biochem. 11 471 The bioreactors were quite stable for over 6 months with monthly rehardening and regeneration of the immobilized cell beads.