``Recycled'' content paper: This term is not specifically defined in any 
  EPA guidance documents or in the statutes, but has come to mean paper 
  containing any of the recovered material categories of fiber, such as 
  postconsumer or cotton (or equivalent).
Reflectance (brightness) drop: Measure brightness on a marked area of 
  the sheet, using method T-452. Expose the marked area in a water-
  cooled xenon-arc lamp, continuous Lamp fading apparatus for 48 
  Standard Fading Hours, using method 16E of the American Association of 
  Textile Chemists and Colorists (One Davis Drive P.O. Box 12215, 
  Research Triangle Park, NC 27709; www.aatcc.org). Recondition the 
  sheet in the standard atmosphere, and again measure the brightness of 
  the marked area. Calculate reflectance drop as the difference between 
  the two brightness results. Report the average reflectance drop of not 
  less than five sheets.
Rosin: See sizing.
Sampling: Sampling shall be conducted in accordance with T-400. Agencies 
  shall specify detailed plans, and criteria for acceptance or 
  rejection, tailored to specific end products, grades, end uses, or 
  other particular conditions. Each agency shall also specify detailed 
  plans for visual examination of lots of paper for properties not 
  included in these Testing Standards. Agencies shall make documents 
  incorporating such plans available to bidders and contractors.
Sizing: (A) For animal glue, use method T-504. (B) For rosin, use method 
  T-408.
Smoothness: Use method T-538.
Speck: A unit of dirt; any foreign matter 0.02 mm<SUP>2</SUP> or larger 
  embedded in the sheet which when examined by reflected light has a 
  contrasting color to the rest of the surface. Use method T-537. Note, 
  in making the visual count, the specks should be visible when the 
  specimen is examined in well lit room at a 45 deg. angle from the 
  normal, 30 to 45 cm (12 to 18 inches) from the surface of the sheet. 
  It is not necessary to lift or rotate the specimen to see the specks. 
  Also see dirt.
Stiffness: Gurley test--use method T-543. Test specimen size is 64 mm 
  long by 51 mm wide. Taber test--use method T-489.
Stock (fiber analysis): Use method T-401, except for those paper 
  specification standards containing the following language:
    ``Free from groundwood and/or unbleached pulp,'' or
    ``100 percent or the remainder bleached chemical (wood) pulp.''
    These requirements shall be interpreted to mean that ``the paper is 
  essentially free from lignin.''
    To evaluate for the presence of lignin, use lignin test method 
  above. Alternatively, use TAPPI T-401 and the Graff C-Stain for fiber 
  analysis. A yellow color reaction shall be interpreted to signify the 
  presence of lignin and shall be sufficient cause for rejection of the 
  paper. Note, (1) In the case of hardwood pulps, the yellow reaction 
  may be masked by the strong blue kraft reaction and thus give the 
  fibers a greenish appearance. See Appendix H.1.2 of T-401 for specific 
  Color descriptions. (2) Some pulps such as BCTMP also produce a yellow 
  reaction to the Graff C-stain. Should this occur, the paper 
  manufacturer should be contacted for a certification of the 
  composition of the fiber furnish used in the manufacture of the paper. 
  If hardwood BCTMP has been used, the lignin content of the paper shall 
  not exceed 3 percent when measured spectrophotometrically.
TCF: See chlorine-free.
Tearing strength (resistance): Use method T-414.
Tensile strength: Use method T-494. For wet tensile strength, heat the 
  specimens at 105  deg.C for 15 minutes, then use method T-456. Report 
  time of the immersion.
Thickness: Use method T-411.
Thread count: Use method 5050 of Federal Test Method Standard No. 191 or 
  D 1910 of ASTM.
Unbleached: Paper or pulp not treated with bleaching agents. See stock.