Hardwood surfaces

Tannin-containing woods can also suffer from dark-brown stains produced by alkali, usually from a concrete or a detergent source. Conversely, fair-faced concrete can be similarly stained by the run-off water from unprotected hardwood surfaces. Some woods, e.g. afzelia, ayan and idigbo, give yellow contaminating dyes with alkaline detergents and should not be used in washrooms and kitchens. 

Lay-up proceeds by laying down the veneer which is to be the back surface of the panel. Then a sufficient number of pieces of core veneer are passed through the glue spreader to form the next layer of cross-oriented veneer. The glue spreader commonly used in hardwood plywood manufacture is a roU coater in which a pair of opposing mbber roUs are coated with a thin layer of adhesive. As the veneer is passed between the roUs, the adhesive is transferred to the surfaces of the veneer. Adhesive is appHed only to the cross-pfles and in sufficient quantity to provide a continuous layer on both opposing faces of veneer. Thus, in the case of a three-ply panel, only the core layer is spread with adhesive and in that of a five-ply panel, the second and fourth layers both of which are cross-pfles, are spread with adhesive. Then the top surface veneer, which is normally the decorative surface, is placed on the assembly. 

When used as substitutes for asbestos fibers, plant fibers and manmade cellulose fibers show comparable characteristic values in a cement matrix, but at lower costs. As with plastic composites, these values are essentially dependent on the properties of the fiber and the adhesion between fiber and matrix. Distinctly higher values for strength and. stiffness of the composites can be achieved by a chemical modification of the fiber surface (acrylic and polystyrene treatment [74]), usually produced by the Hatschek-process 75-77J. Tests by Coutts et al. [76] and Coutts [77,78] on wood fiber cement (soft-, and hardwood fibers) show that already at a fiber content of 8-10 wt%, a maximum of strengthening is achieved (Fig. 22). 

Modern charcoal retorts are charged with wood, biowaste (bark, sawdust, etc.), peat, and sometimes low-rank coals. Yield and properties (hardness, density, surface area, etc.) can vary widely so the desired end use must be considered. Charcoal from coniferous trees is soft and porous, while that from hardwoods is dense and strong. For barbecuing, charcoal is usually compressed into briquettes, with binders and additives chosen to improve handling and ease of ignition. 

Aluminum-based primer plus alkyd finish The binder for these primers is normally oleo-resinous but the pigmentation is aluminum flake. This type is preferred for hardwoods and softwoods where knots or resinous areas predominate. They do not give such a smooth surface as primers without aluminum. 

The commonest staining trouble is iron stain —the blue-black stain caused by the interaction of soluble iron corrosion products and the natural tannins in wood. Hardwoods are generally more susceptible than softwoods. Steel wool should not be used for smoothing wood surfaces. Iron stains, if not too severe, can be removed with oxalic acid. Heavy contamination with soluble iron corrosion products usually results in migration and conversion to rust deposits in the wood. 

Cellulose fibres produced from hardwoods, with various chemical surface treatments to ensure that they are compatible with rubbers, can be used to produce high modulus vulcanisates. The bond between rubber and fibres is created during vulcanisation. These fibres can be used to reinforce extruded hoses gaining orientation in the direction of flow. There is a range of fibres available which are compatible with different rubber types. 

For battery separators, regenerated cellulose is placed on the surface of nonwoven so that the nonwoven is available to promote the wicking of the electrolyte. The nonwovens should not allow the penetration of viscose into itself. Suitable nonwovens are made from polypropylene, poly(vinyl alcohol), and hardwood hemps. Regenerated cellulose films are commonly used in alkaline manganese cells, both primary and secondary, in NiCd industrial batteries, as well as in silver—zinc batteries. 

The safest types of floors are untreated hardwood, true linoleum (the natural material, not the vinyl imitation), ceramic tile, marble, and stone slate. Cork is becoming more popular because it s warmer than tiles and, like linoleum, resilient—a forgiving surface for rolling, tumbling babies and toddlers. Brick, marble, and other stone tiles are more costly but also good choices. The following stores will have what you need. 

Figure 5. Cross-sectional and longitudinal surfaces of a ring-porous hardwood. In the cross-sectional view (X) the largest diameter cells are springwood vessels whereas the smaller cells with obvious openings are sum-merwood vessels. Smaller diameter thick-walled fibers constitute most of the remaining volume. Transversely oriented food-storing cells can be seen on the radial surface (arrow). 40X (Courtesy of N. C. Brown Center for Ultrastructural Studies, S.U.N.Y. College of Environmental Science and Forestry)...

After veneers have been unitized from small strips to full sheets of the desired width, usually 4 feet by 8 feet in softwood plywood and various widths and lengths for hardwood custom manufactured plywood, they are ready to be fed through a glue application which coats one or both sides of veneer sheets with liquid adhesive. These applicators control the amount of adhesive transferred to the veneer. The amount of glue mix applied per 100 square feet of surface area (single glue line basis) will approximate 4-5 pounds and the amount of resin solids 1-1.5 pounds. 

Manufacture. The basic tools for tapa production are a hardwood anvil and beater. Two to four layers of the bark are laid out on the anvil which has a smooth and slightly convex surface. Heavy, widely grooved mallets are used at the beginning of the beating process to spread and felt the fibers. More finely grooved, lighter... 

Solvent Wash. Hardwood, porcelain, glass, metal and similar hard-surfaced items lend themselves to the solvent wash technique of recovery. Usually, no odors can be detected and indications are that a very small quantity of only the high-boiling fractions of an accelerant remain for recovery. 

The warty layer (W) is a thin amorphous membrane located in the inner surface of the cell wall in all conifers and in some hardwoods, containing warty deposits of a still unknown composition. Each species has its own, characteristic warty layer. 

The dislodgeability of a pesticide residue may depend on the condition of the surface. For example, new carpets are typically more stain-resistant and have more uniform piles, and thus they may behave differently than soiled and worn carpets. The presence of excessive moisture levels in carpeting, as may be the case shortly after a wet cleaning operation, may also affect the dislodgeability of residues, possibly yielding higher than normal results. Wax on vinyl and hardwood floors may affect dislodgeability, as may pits, cracks and crevices in the surface. 

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