Optical finishes

Physical finishing methods for textiles include optical finishing, brushing and napping, softening, shearing, and compacting of the textile structure. 

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Corundum or alumina is again faster than emery, but it is much more expensive. Finally, diamond powder can be twed, and is very fast but by far the most expensive. Once the glass has been ground it can be polished with jeweller s rouge or Cerirouge (see p. 83). With these polishes an optical finish may be obtained. 

Let us now concentrate on the specific sample used in this work. For the bulk appKTP crystal (used experimentally in section 7), the commercially-obtained KTP wafer was flux-grown, c-cut, single domain, 1 mm thick, and with the c-faces polished to an optical finish. For practical reasons, the wafers were cut into 10x5 mm pieces after the conductivity measurements. 

To make the white spot lesions, human premolars were coated with nail polish except for a 5-mm square on their buccal surfaces. This ensured that demineralization always occurred at a specific location. The samples were then immersed in 200 ml methyl cellulose gel with 200 ml lactic acid solution (pH 4.6) poured on top, but separated by a sheet of filter paper. The teeth were stored in this solution at 3 7°C for 14 days to allow the lesions to develop. After removal from the gel, the teeth were washed and sectioned through the center of the lesions to enable the cross-section of each lesion to be viewed. The two cross-sections created for each lesion were then mounted in a low temperature cure epoxy and polished to an optical finish using 1/4-micron grit (diamond paste). 

The anvil seats transmit a force to the anvil tables of the order of 10 kN. Thus the seats are subjected to a normal stress of some 2 GPa, for a 3 mm diameter table. This value may well be exceeded for ultrahigh-pressure work. Thus seats are most often made of tungsten carbide with an optical finish. In some X-ray measurements, beryllium seats have to be used, for their transparency. The mechanical performance is then drastically decreased, and the beryllium must be machined in specialized workshops. Single-crystal sapphire has been used, to provide an increased optical aperture. ... 

Also referred to as median vent cracks, these are caused to pop-in by exceeding a critical indenter load. It is the pop-in phenomenon that is important to the development of this subject in ceramic science because the halfpenny crack has the surface trace which allows opaque materials to be analyzed by recording the radial crack size as a function of increasing load. There is, however, the implication that the surface must be prepared carefully by polishing to an optical finish in order to see the radial cracks. If necessary, samples must be annealed to remove polishing stresses. Radial cracks are the result of surface tensile stresses, (Xyy in equation (1.29). Such stresses are at a maximum at the elastic-plastic boundary. 

It must be re-emphasized that surfaces should have an optical finish to find crack length accurately and measurements should be made as fast as possible after indentation because ambient conditions can lead to corrosion growth of cracks and hence lower values of Kc as Section 5.11 clearly shows. 

Perfectly spherical spheres of a wide variety of sizes with optical finish can be produced from near-spherical starting blocks by grinding and lapping on optical finishing machines. 

Many natural fibers and some synthetic fibers possess a degree of yellow coloration and must be bleached to brighten and remove yellow coloration from the textile substrate prior to dyeing and/or finishing. Since bleaching is a chemical finishing technique, it is discussed in Chapter 18 under Optical Finishes. 

Optical Finishes Optical finishes do little to affect the color of a textile substrate, but rather act to destroy or mask color centers. They may either brighten the textile, making it more reflective, or deluster the textile, making it less reflective, depending on the treatment. 

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