Commercial Uses for Redwood Bark Dust

Sulfonated and caustic extracts of the valuable redwood bark dust fraction are gaining wide use in ore flotation, drilling muds, water treatment, and other dispersing, emulsifying, and reacting roles. Barks are variable in chemical composition and anatomy, and the methods of processing them must necessarily be tailored to the specific raw material at hand. Thus, bark of Douglas-fir or ponderosa pine might be reduced by grinding, whereas a fibrous bark such as that from redwood or cedar might better be hammermilled to retain its inherent fibrous structure. The cork fraction of Douglas-fir bark is most rich in tannin-like materials, whereas the dust fraction of redwood bark has the highest yield of extractives. The usefulness of bark as an insulator is due to its inherent permanence and durability, its high factor of resilience, and its low thermal conductivity. The coarse fraction of redwood bark and a finer amorphous fraction are used very successfully as soil conditioners and as growing media for orchids. Coarse redwood bark fiber is also used as an additive to oil-well drilling muds to seal off areas of circulation loss in the strata. Its felting and bridging qualities make it ideal for this purpose. More refined grades of redwood bark fiber are suitable for dry or wet felting operations, and for automotive air and oil filters. Two redwood bark extracts, palcotan and palconate, are well known in a variety of industries where their dispersing, emulsifying, and reactive characteristics arc employed. Both the caustic and sulfonated extracts have been used as a replacement for quebracho in the flotation of fluorspar from lime minerals and in the depression of calcite in the flotation of apatite from calcareous gangue. Palcotan is a direct replacement for quebracho in the deflocculation of calcium sludges in boiler waters. Bark appears to be a desirable constituent in charcoal prepared from slab wood.

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