The article presents research evaluating non-aqueous deacidification treatments for paper documents. Experiments tested alcoholic solutions of barium hydroxide and magnesium acetate, and an improved magnesium methoxide spray treatment; aqueous deacidification (Barrow technique) was performed for comparison. Several improvements in working procedures are outlined. Chemical analysis and physical testing included measurement of: pH (cold extraction), carboxyl group content, brightness, degree of polymerization (DP), tensile strength, stretch, fold endurance, and tear resistance; thermal aging and exposure to different relative humidity (RH) conditions (dry aging and moist aging) were done. It was concluded that alcoholic magnesium acetate cannot be recommended (causes cellulose deterioration). Immersion in barium hydroxide in methanol is the safest conservation method; fire and health hazards due to evaporation of solvent are noted. Soaking for 15-30 minutes in a relatively dilute solution of 0.018 N (2.84 g Ba(OH)₂.8H₂O is usually adequate and minimizes discoloration, with 10 g/l of paper in treatment a conservative recommendation. Stronger solutions can be used if immersion is impossible, but are not recommended for normal use. The magnesium methoxide spray proved interesting, with some disadvantages (discoloration, expense).