While there are many different kinds of tobacco products (e.g., cigarettes, cigars, cigarillos, bidis, kreteks, pipe tobaccos, and smokeless products), the most common form of tobacco is the manufactured cigarette.
A cigarette is a cylindrical roll of tobacco material mass contained in a non-tobacco or paper wrapper. Machine manufactured cigarettes (15-20,000/min) can be found in 5-8 mm in diameter and 70 -100 mm in length, predominately with a 15-25 mm in length matching diameter cellulose acetate filter plug. This plug is wrapped with a porous wrap which is often coated with a silicone treated colored filter tipping paper.
The manufactured cigarette is a highly engineered device in which all physical elements of the cigarette are carefully controlled, such as packing density, particle size distribution (PSD), rag cut per inch (cpi), color appearance, resistance to draw (RTD), tobacco, and tobacco derived blend composition. The raw materials are predominately tobacco (ca. 50 % w/w) and materials derived from tobacco, but these materials are often augmented with cellulose fibers from wood pulp. The raw material, tobacco, is the source of nicotine, the cigarette structural support, and the source of the myriad of smoke components.
Only a portion of the tobacco inside a cigarette comes from the leaf of a tobacco plant. A significant amount of the shredded brown innards of most modern cigarettes is a paper product called "reconstituted tobacco" or "homogenized sheet tobacco," which is made from a pulp of mashed tobacco stems and other parts of the tobacco leaf that would otherwise go to waste. Manufacturers spray and impregnate reconstituted tobacco paper with nicotine and other substances lost during the process, along with as many as 600 chemical additives. These include several that may come as a surprise, such as ammonia, which aids in the delivery of nicotine, and chocolate, which masks the bitter taste of tobacco. Finally, the 'recon' is sliced to resemble shredded leaf tobacco.
In addition to reconstituted tobacco, cigarette companies pack cigarettes with so-called puffed tobacco (also called "expanded tobacco"), which allows them to produce more cigarettes per pound of tobacco grown with lower levels of tar particles in the smoke. Manufacturers saturate this tobacco, which they make from the leaf of the plant, with Freon and ammonia gases and then freeze-dry it. This process expands the tobacco, increasing its volume to at least double its natural state.
Though seemingly innocuous, cigarette paper is largely responsible for the rate at which a cigarette burns and the amount and density of the smoke it produces. The paper displays a pattern of concentric circle striations called "burn rings." The burn rings correspond to two different thicknesses in the paper, which serve to precisely control the speed at which the cigarette burns, slowing it automatically when the smoker is not inhaling in order to prolong the cigarette's consumption and speeding it up as the smoker takes a drag so as to maximize smoke intake. In addition, like the tobacco, the cigarette paper contains a host of chemicals, among them titanium oxide, which accelerates and maintains burning so the cigarette does not go out and the smoke is delivered evenly with each puff. These chemicals have contributed to many cigarette-caused fires, a problem that some manufacturers have not addressed until recently.
The filter cigarette was a specialty item until 1954, when manufacturers introduced it broadly following a spate of speculative announcements from doctors and researchers concerning a possible link between lung diseases and smoking. Reacting to smokers' voiced fears and sudden reduced cigarette consumption, cigarette companies, by altering the filter's structure and materials, began making competing claims about how low their brands' tar and nicotine levels were.
The cellulose acetate tow in a filter is a web of fibers made from wood pulp. In manufacturing, the filter material arrives as a single long band of over 10,000 fibers pressed into large 750 kg bales. In a filter maker, this band of compact fibers is mechanically stretched to open the fibers up, sprayed with a plasticizer to bind them together, wrapped with thin paper, cut, and fed into a cigarette-making machine.
Some cigarettes today boast the inclusion of a "charcoal filter" in addition to the more common dense, synthetic fiber filters seen in almost all filter cigarettes. Manufacturers claim that charcoal filters, which contain bits of charcoal embedded within the fiber filters, reduce certain toxins in the smoke. But no evidence exists that these cigarettes are significantly less dangerous for the user.
Most filter cigarettes also bear ventilation holes punched around the circumference of the filter tip. (Regular cigarettes might feature one ring of ventilation holes, while light and ultra-light cigarettes of the same brand might have two or more rings.) These tiny holes, which you can see by holding the unrolled paper up to a bright light, can allow enough fresh air into the smoke that such cigarettes can test quite low in tar and nicotine levels when smoked by machines, which do not cover the holes. However, smokers' fingers or lips often cover some of these holes as they puff, giving them much higher doses of tar and nicotine than advertised. According to critics of the tobacco industry, the holes create a flexible dosing system that allows addicted smokers to maintain the tar and nicotine levels they crave while believing they are receiving lower, safer doses.
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