Fuller's Soap (בֹּרַית מכִבּשֵׁים, borith' mekabbeshin', alkali of those treading cloth, i.e., washers' potash; Sept. ποία πλυνόντων), some alkaline or saponaceous substance mixed with the water in the tubs used for stamping or beating cloth. Two substances of the nature are mentioned in Scripture: נֶתֶר, nether, nitre (νίτρον, nitrum, Pr 25:20; Jer 2:22), and בֹּרַית, borith', soap (ποία, herba fullonum, herba borith, Mal 3:2)
Nitre is found in Egypt and in Syria, and vegetable alkali was also obtained there from the ashes of certain plants, probably Salsola kali (Gesenius, Thesaur. Heb. page 246; Pliny, 31:10, 46; Hasselquist, page 275; Burckhardt, Syria, page 214). The juice also of some saponaceous plant, perhaps Gypsaphila struthium, or Saponaria officinalis, was sometimes mixed with the water for the like purpose, and may thus be regarded as representing the soap of Scripture. Other substances also are mentioned as being employed in cleansing, which, together with alkali, seem to identify the Jewish with the Roman process (Pliny, 35:57), as urine and chalk (creta cimolia), and bean-water, i.e., bean-meal mixed with water (Mishna, Shabb. 9:5; Niddah, 9:6). Urine, both of men and of animals, was regularly collected at Rome for cleansing cloths (Plin. 38:26, 48; Athen. 11, page 484; Mart. 9:93; Plautus, Asin. 5:2, 57); and it seems not improbable that its use in the fullers trade at Jerusalem may have suggested the coarse taunt of Rabshakeh during his interview with the deputies of Hezekiah in the highway of the fullers field (2Ki 18:27); but Schottgen thinks it doubtful whether the Jews made use of it in fulling (Antiq. full. § 9). The process of whitening garments was performed by rubbing into them chalk or earth of some kind (אִשׁלִג). Creta cimolia (cimolite) was probably the earth most frequently used ("cretae fullonise," Pliny, 17:4; compare Theophr. Charact. 11). The whitest sort of earth for this purpose is a white potters clay or marl (Hoffmann, Handb. d. Min. eral, II, 2:230 sq.), with which the poor at Rome rubbed their clothes on festival days to make them appear brighter (Pliny, 31:10, § 118; 35:17). Sulphur, which was used at Rome for discharging positive color (Plin. 35:57), was abundant in some parts of Palestine, but there is no evidence to show that it was used in the fullers trade. The powerful cleansing properties of borith or soap are employed by the prophet Malachi as a figure under which to represent the prospective results of Messiah's appearance (Mal 3:2). See Beckmann, Hist. of 1nv. 2:92, 106, edit. Bohn,; Saalschttz, 1:3, 14, 32; 2:34, 6; Smith, Dict. of Classical Antiq. s.v. Fullo. SEE SOAP.