Reeds or related cellulosics are treated for flame proofing and fire retardancy by a soln. contg. 1050 wt.% diammonium-hydrogen-phosphate and 0.05-0.5 wt.% sulphate type surfactant at 40-90 deg.C., pH 6-8 for 1-60 mins.. Further treatment at 5-35 deg.C., pH 6-9 follows until the reeds absorb 0.05-0.5 times of their original wt. Reeds are then natural or force air-dried. Pretreated reeds are coated by a mixt. contg. 6-30 pts. wt. expanded perlite of 2 mm grain size and/or 10-100 pts. wt. aluminium-oxide-hydrate, and/or 10-50 pts. wt. bentonite gel (10% solids), and/or 5-50 pts. wt. water glass soln. (50% solids), 5-30 pts. wt. hollow glass-spheres, 30-100 pts. wt. water, 0.1-2 pts. wt. ammonium-hydrogen-phosphate, 10-100 of a urea-formaldehyde condensate (40-60 wt.% solids) and 1:1-1:2 water compatibility, 0.5-5 pts. wt. ammonium-chloride and 3-30 pts. wt. of a 40-60% solids as dispn. copolymer of vinylacetate-versotate or vinyl-acetate-butyl-acrylate, each of 130000-170000 average mol. wt. and 30-100 wt.% vinyl-acetate content
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