Birch bark manuscripts from archaeological sources should be washed in hot (over 80°C (176°F)) distilled water baths, changed as they become dirty and the temperature drops. This hot-water treatment is essential before rolled manuscripts are unrolled, according to research done in the Soviet Union on manuscripts from Novgorod. It was noted that content of water-soluble salts of calcium, sodium and magnesium was much higher in archaeological birch bark than in newly prepared examples. This is believed to be the cause of cracking of manuscripts in storage which were not thoroughly washed. The final wash should include a disinfectant: 1% aqueous sodium pentachlorophenolate is recommended. Surface stabilization, if necessary, may be done with methylolpolyamide glue PF-2/1. Storage between two pieces of glass held with neutral tape is recommended.