What is "caustic surface"

Caustic \Caus"tic\, Caustical \Caus"tic*al\, a. [L. caustucs, Ge. ?, fr. ? to burn. Cf. Calm, Ink.]

1. Capable of destroying the texture of anything or eating away its substance by chemical action; burning; corrosive; searing.

2. Severe; satirical; sharp; as, a caustic remark.

   Caustic curve (Optics), a curve to which the ray of light, reflected or refracted by another curve, are tangents, the reflecting or refracting curve and the luminous point being in one plane.

   Caustic lime. See under Lime.

   Caustic potash, Caustic soda (Chem.), the solid hydroxides potash, KOH, and soda, NaOH, or solutions of the same.

   Caustic silver, nitrate of silver, lunar caustic.

   Caustic surface (Optics), a surface to which rays reflected or refracted by another surface are tangents. Caustic curves and surfaces are called catacaustic when formed by reflection, and diacaustic when formed by refraction.

   Syn: Stinging; cutting; pungent; searching.

Surface \Sur"face`\, n. [F. See Sur-, and Face, and cf. Superficial.]

1. The exterior part of anything that has length and breadth; one of the limits that bound a solid, esp. the upper face; superficies; the outside; as, the surface of the earth; the surface of a diamond; the surface of the body.

   The bright surface of this ethereous mold.
   --Milton.

2. Hence, outward or external appearance.

   Vain and weak understandings, which penetrate no deeper than the surface.
   --V. Knox.

3. (Geom.) A magnitude that has length and breadth without thickness; superficies; as, a plane surface; a spherical surface.

4. (Fort.) That part of the side which is terminated by the flank prolonged, and the angle of the nearest bastion.
   --Stocqueler.

   Caustic surface, Heating surface, etc. See under Caustic, Heating, etc.

   Surface condensation, Surface condenser. See under Condensation, and Condenser.

   Surface gauge (Mach.), an instrument consisting of a standard having a flat base and carrying an adjustable pointer, for gauging the evenness of a surface or its height, or for marking a line parallel with a surface.

   Surface grub (Zo["o]l.), the larva of the great yellow underwing moth ( Triph[oe]na pronuba). It is often destructive to the roots of grasses and other plants.

   Surface plate (Mach.), a plate having an accurately dressed flat surface, used as a standard of flatness by which to test other surfaces.

   Surface printing, printing from a surface in relief, as from type, in distinction from plate printing, in which the ink is contained in engraved lines.

n. (context optics English) A surface to which rays reflected or refracted by another surface are tangents.