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A glass knife is a knife with a blade made of glass, with a fracture line forming an extremely sharp cutting edge.
Glass knives were used in antiquity due to their natural sharpness and the ease with which they could be manufactured. In modern electron microscopy glass knives are used to make the ultrathin sections needed for imaging.
In the Stone Age, bladed tools were made by chipping suitable stones which broke with a conchoidal fracture, a process known as knapping or lithic reduction. The same technique was used to make tools, including knives, out of obsidian, natural volcanic glass.
From the 1920s until the 1940s, Dur-X glass fruit and cake knives were sold for use in kitchens under a 1938 US Patent. [1] Before the wide availability of inexpensive stainless steel cutlery, they were used for cutting citrus fruit, tomatoes and other acidic foods, the flavor of which would be tainted by steel knives and which would stain ordinary steel knives. They were molded in tempered glass, with a cutting edge ground sharp. [2] [3]
While glass knives as such are no longer in general use, knives with ceramic blades made from zirconium dioxide have been available since the mid-1980s, with a very sharp and long-lasting edge produced by grinding rather than fracturing. [4]
Modern glass knives were once the blade of choice for the ultra-thin sectioning required in transmission electron microscopy because they can be manufactured by hand and are sharper than softer metal blades because the crystalline structure of metals makes it impossible to obtain a continuous sharp edge. [5] The advent of diamond knives, which keep their edge much longer and are more suitable for cutting hard materials, quickly relegated glass knives to a second-rate status. However, some labs still use glass knives because they are significantly less expensive than diamond knives. A common practice is to use a glass knife to cut the block which contains the sample to near the location of the specimen to be examined. Then the glass knife is replaced by a diamond blade for the actual ultrathin sectioning. This extends the life of the diamond blade which is used only when its superior performance is critical.[ citation needed ]
Obsidian, a naturally occurring volcanic glass, is used to make extremely sharp surgical scalpels, significantly sharper than is possible with steel. The blades are brittle and very easily broken.
Glass knives can be produced by hand using pliers with two raised bumps on one jaw and a single bump between the two bumps on the opposing jaw, but special machines called "knife-makers" are used in most electron microscopy laboratories to ensure repeatable results. The glass used typically starts out as 1-inch-wide (25 mm) strips of 1⁄4-inch-thick (6.4 mm) plate glass, which is cut into 1 inch (2.5 cm) squares. The glass square is then scored across the diagonal with a steel or tungsten carbide glass-cutting wheel to determine where the square will break, and pressure is then applied gradually across the opposite diagonal until the square breaks. This technique provides two usable knife edges, one on each of the two resulting triangles. The better the break is aligned with the diagonal, the better the cutting edge. [5] [6]
A utility knife is any type of knife used for general manual work purposes. Such knives were originally fixed-blade knives with durable cutting edges suitable for rough work such as cutting cordage, cutting/scraping hides, butchering animals, cleaning fish scales, reshaping timber, and other tasks. Craft knives are small utility knives used as precision-oriented tools for finer, more delicate tasks such as carving and papercutting.
A knife is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least 2.5 million years ago, as evidenced by the Oldowan tools. Originally made of wood, bone, and stone, over the centuries, in step with improvements in both metallurgy and manufacturing, knife blades have been made from copper, bronze, iron, steel, ceramic, and titanium. Most modern knives have either fixed or folding blades; blade patterns and styles vary by maker and country of origin.
Obsidian is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock.
A scalpel, lancet, or bistoury is a small and extremely sharp bladed instrument used for surgery, anatomical dissection, podiatry and various handicrafts. A lancet is a double-edged scalpel.
A blade is the sharp, cutting portion of a tool, weapon, or machine, specifically designed to puncture, chop, slice, or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are intended to cut. This includes early examples made from flaked stones like flint or obsidian, evolving through the ages into metal forms like copper, bronze, and iron, and culminating in modern versions made from steel or ceramics. Serving as one of humanity's oldest tools, blades continue to have wide-ranging applications, including in combat, cooking, and various other everyday and specialized tasks.
A Japanese kitchen knife is a type of kitchen knife used for food preparation. These knives come in many different varieties and are often made using traditional Japanese blacksmithing techniques. They can be made from stainless steel, or hagane, which is the same kind of steel used to make Japanese swords. Most knives are referred to as hōchō or the variation -bōchō in compound words but can have other names including -kiri. There are four general categories used to distinguish the Japanese knife designs: handle, blade grind, steel, and construction.
A blade's grind is its cross-sectional shape in a plane normal to the edge. Grind differs from blade profile, which is the blade's cross-sectional shape in the plane containing the blade's edge and the centre contour of the blade's back. The grind of a blade should not be confused with the bevel forming the sharpened edge; it more usually describes the overall cross-section of the blade, not inclusive of the beveled cutting edge which is typically of a different, less acute angle as the bevel ground onto the blade to give it a cross-sectional shape. For example, the famous Buck 110 hunting knife has a "hollow ground" blade, with concave blade faces, but the cutting edge itself is a simple, flat-ground bevel of lesser angle. It would be difficult, if not impossible, to put a "hollow grind" onto the actual cutting edge of the blade itself, which is a very narrow and small bevel.
A microtome is a cutting tool used to produce extremely thin slices of material known as sections, with the process being termed microsectioning. Important in science, microtomes are used in microscopy for the preparation of samples for observation under transmitted light or electron radiation.
A kitchen knife is any knife that is intended to be used in food preparation. While much of this work can be accomplished with a few general-purpose knives – notably a large chef's knife, a tough cleaver, a small paring knife and some sort of serrated blade – there are also many specialized knives that are designed for specific tasks. Kitchen knives can be made from several different materials.
In cooking, a chef's knife, also known as a cook's knife, is a cutting tool used in food preparation. The chef's knife was originally designed primarily to slice and disjoint large cuts of beef. Today it is the primary general-utility knife for most Western cooks.
A serrated blade has a toothlike rather than a plain edge, and is used on saws and on some knives and scissors. It is also known as a dentated, sawtooth, or toothed blade. Many such blades are scalloped, having edges cut with curved notches, common on wood saws and bread knives.
Sharpening stones, or whetstones, are used to sharpen the edges of steel tools such as knives through grinding and honing.
Sharpening is the process of creating or refining the edge joining two non-coplanar faces into a converging apex, thereby creating an edge of appropriate shape on a tool or implement designed for cutting. Sharpening is done by removing material on an implement with an abrasive substance harder than the material of the implement, followed sometimes by processes to polish/hone the sharp surface to increase smoothness.
A ceramic knife is a knife with a ceramic blade typically made from zirconium dioxide (ZrO2; also known as zirconia), rather than the steel used for most knives. Ceramic knife blades are usually produced through the dry-pressing and firing of powdered zirconia using solid-state sintering. The blades typically score 8.5 on the Mohs scale of mineral hardness, compared to 4.5 for normal steel and 7.5 to 8 for hardened steel and 10 for diamond. The resultant blade has a hard edge that stays sharp for much longer than conventional steel blades. However, the blade is brittle, subject to chipping, and will break rather than flex if twisted. The ceramic blade is sharpened by grinding the edges with a diamond-dust-coated grinding wheel.
Knife making is the process of manufacturing a knife by any one or a combination of processes: stock removal, forging to shape, welded lamination or investment cast. Typical metals used come from the carbon steel, tool, or stainless steel families. Primitive knives have been made from bronze, copper, brass, iron, obsidian, and flint.
Knife sharpening is the process of making a knife or similar tool sharp by grinding against a hard, rough surface, typically a stone, or a flexible surface with hard particles, such as sandpaper. Additionally, a leather razor strop, or strop, is often used to straighten and polish an edge.
A honing steel, sometimes referred to as a sharpening steel, whet steel, sharpening stick, sharpening rod, butcher's steel, and chef's steel, is a rod of steel, ceramic or diamond-coated steel used to restore keenness to dulled blade edges. They are flat, oval, or round in cross-section and up to 30 centimetres (1 ft) long. The steel and ceramic honing steels may have longitudinal ridges, whereas the diamond-coated steels are smooth but embedded with abrasive diamond particles.
A diamond knife is a very sharp knife in which the edge is made from diamond, invented by Humberto Fernández-Morán in 1955. Diamond knives are used for medical and scientific applications where an extremely sharp and long-lasting edge is essential. The knives are very expensive to purchase, depending on the quality and size of the knife; in addition the knives must be professionally sharpened as the edge dulls.
A macuahuitl is a weapon, a wooden club with several embedded obsidian blades. The name is derived from the Nahuatl language and means "hand-wood". Its sides are embedded with prismatic blades traditionally made from obsidian. Obsidian is capable of producing an edge sharper than high quality steel razor blades. The macuahuitl was a standard close combat weapon.
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