Knife scratches

Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal is likely to ignite if scratched with a knife. 

Hardness. Most limestone is soft enough to be readily scratched with a knife. Pure calcite is standardized on Mohs scale at 3 aragonite is harder, 3.5—4. Dolomitic limestone is generally harder than high calcium. Dead-burned or sintered limes are 3—4 on this scale, whereas most commercial soft-burned quicklimes are 2—3 (see Hardness). 

Artifacts introduced through sample preparation are common materials these may be bits of facial tissue, wax, epithelial cells, hair, or dried stain, all inadvertently introduced by the microscopist. Detergent residues on so-called precleaned microscope slides and broken glass are common artifacts, as are knife marks and chatter marks from sectioning with a faulty blade, or scratch marks from grinding and polishing. 

Fused silica is slightly more brittle than borosilicate glasses and is therefore more easily fractured. Tubes up to just over 1 cm in diameter can be snapped with the fingers after scratching with a file or glass knife. Any ragged end so formed can be cleaned up with an abrasive wheel. 

Knife test (KNF) The test is done by making two intersecting scratches through the paint film to the substrate with a sharp steel knife. Adhesive or cohesive failures are evaluated by peeling the coating from the intersection point and outwards. Common for the three adhesion evaluation methods are that the test is performed on immersed and non- immersed panel-half (referred to as respectively "wet" and "dry" adhesion). The type of rupture is reported, and the severity is judged on a scale from 5 (perfect) to 0 (poor). 

Cerium is a grayish/iron-colored, very reactive metallic element that is attacked by both acids and alkalies. Pure cerium will ignite if scratched with a knife, but it can be combined safely with many other elements and materials. It is relatively soft and both malleable and ductile. 

What is it about gold that makes it so attractive and so useful Gold is not very hard a knife can easily scratch pure gold and it is very heavy or even dense for a metallic mineral. Some of the other characteristics of gold are ductility, malleability and sectility, meaning it can be stretched into a wire, pounded into other shapes, and cut into slices. Gold is the most ductile and malleable element on our planet. It is a great metal for jewellery because it never tarnishes. 

In a relative sense, minerals from 2 in 33) hardness can be scratched by a fingernail 4 by a penny, and 5 to 6 by a knife blade or piece of glass This scale is strictly relative and noidincur because there is a much wider differential, lor example, hetween corundum and diamond than between... 

Imagine the possibilities, some of which are just now becoming reality Tools, knife blades, and scalpels coated with diamond remain forever sharp. Eyeglass lenses and wristwatches coated with diamond remain scratch-free. High-fidelity loudspeakers coated with diamond give a nearly perfect, undistorted sound at high frequencies. Hip joints and other biological implants coated with diamond are not rejected by the body s immune system. 

COCAINE BUGS Hallucinations that feel like bugs crawling under the skin, occurring in heavy or binge users of cocaine. This sensation can be so intense that users will scratch their skin or use a knife to attempt to remove the bugs. 

We know that diamond can scratch glass, but so can hard metals such as the hardened steel of a file or a tungsten-carbide glass knife. A beaker that is slid or... 

FIG. 4.5. h on wire hooks. Tlie glass tube is scratched witli a knife or file, tlie wire hook is heated to cheiiy red. Hie tube is held horizontally and rotated witli the scratch in contact witli the hot wiie. A crack will immediately appear and travel round the tube, leaving a clean straight cut end. 

The tube is mounted in the lathe and a straight circumferential scratch made on the outside surface by holding the edge of a tungsten-carbide knife against the rotating tube. Alternatively, the scratch may be made with a suitably mounted diamond point. 

If too much Canada balsam has been used, some of it usually spreads beyond the edge of the cover-glass, or on its surface. In this event wait until the balsam hardens, when it can be scratched off with a knife, and the surface of the glass cleaned with a rag moistened with turpentine oil or xylol. 

IvveguZ T geZation can take many forms. Streaks or draglines may appear at the top side of the membranes that is, the surface which constitutes the air/solution interface during the nascent phases of membrane formation. If a solution is close to the point of incipient gelation when it passes under the casting knife and is first exposed to air, virtually any imperfection, such as a scratch... 

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