What is "crisping iron"

Crisp \Crisp\, v. t. [imp. & p. p. Crisped (kr?spt); p. pr. & vb. n. Crisping.] [L. crispare, fr. crispus. See Crisp. a. ]

1. To curl; to form into ringlets, as hair, or the nap of cloth; to interweave, as the branches of trees.

2. To cause to undulate irregularly, as crape or water; to wrinkle; to cause to ripple. Cf. Crimp.

   The lover with the myrtle sprays Adorns his crisped tresses.
   --Drayton.

   Along the crisped shades and bowers.
   --Milton.

   The crisped brooks, Rolling on orient pearl and sands of gold.
   --Milton.

3. To make crisp or brittle, as in cooking.

   Crisping iron, an instrument by which hair or any textile fabric is crisped.

   Crisping pin, the simplest form of crisping iron.
   --Is. iii. 22.