For some time the user community, and especially brush producers and sellers, have had issues in understanding the Synthetic Fiber Generation concept and in many cases total misunderstandings of the concept. It may be well served at this point to clarify some issues that have arisen over time and misconceptions as corrections as to how the concept is applied. The discussion will center around the most frequently asked issues.Issue 1: The fibers for each Generation are exactly the same with no variation between fibers. The fibers from company X is exactly like company Y.Clarification: That is false. Generations are based on a class of synthetic fibers or a grouping with a given set of parameters for feel when dry to the skin and feel when wet to the skin. So these are a group class of similar fibers not an exact chemical composition equivalency or exact size and diameter equivalency between fibers used by different shaving brush manufacturers.Issue 2: Shaving brush manufacturers X and Y (for example) makes their own fibers.Clarification: All shaving brush manufacturers purchase the fibers from major fiber manufacturing companies who have supplied fibers for the cosmetic industry for over three decades. Fiber manufacturing is a very capital intensive business requiring major chemical production facilities which small size shaving brush companies would not have the ability to develop or manage due to economies of scale and technical issues. See the following articles discussing of how the cosmetic brush industry provided the stock for the synthetic shaving brush makers.Issue 3: What distinguishes each Generational class from each other?Clarification: There are four classes of Synthetic Fibers and that reflects the grouping which mostly has to do with feel when dry to the skin and feel when wet to the skin.The first grouping of fibers is referred to as Generation 1. Generation 1 fibers were developed in the 1930s and took off in the late 1940s. Generation 1 fibers are simple nylon monofilament fibers that were used in shaving brushes to fishing line. Basically this fiber was used for over 50 years. Generally the color was white and the feel to the skin dry was very stiff and the feel to the skin wet was harsh and prickly. Some people have stated that brushes using Generation 1 fibers were closer to being a wire brush than a shaving brush. So the hallmarks of a Generation 1 fibers is very stiff, prickly fibers. More harsh than simple scritch, but border lining on or to some users complete scratch.The second grouping of fibers is referred to as Generation 2. The fibers for these brushes came from the cosmetic fiber industry but were not the highest of the line fibers. The colors were changeable to accommodate what the user most likely expected in a shaving brush, or what the manufacturers user most likely expected in a shaving brush. These fibers were not simply a round monofilament fiber but has some rudimentary patterns and channels cut at the micro level to try to retain some water. The tips were softer than Generation 1 brushes but the fibers were still fairly stiff when rubbed against dry skin. These would fibers were scritchy and tended to cling to each other when wet increasing the stiffness factor. So the hallmarks of Generation 2 fibers is somewhat stiff fibers with scritchy tips when wet. Some individuals still use and enjoy brushes using Generation 2 fibers.The third grouping of fibers is referred to as Generation 3. The fibers for these brushes came from the cosmetic fiber industry but were among the highest of the line fibers available from the industry. The difference of these fibers is that they are very pliable and soft a the tips both when wet and when dry. With a Generation 3 fiber the skin can detect the fiber tips as being hair like when dry but very soft. In fact Generation 3 fibers have a high level of tip definition, which can be easily identified when dry. When wet, the fibers have improved channeling and patterns in the micro level that allow more water to be held, but not nearly as much as naturals that absorb water. So the hallmarks of Generation 3 fibers is fiber that mimics natural hair much more than Generation 1 or 2 in terms of pliability, better control of water application, high level of tip definition, soft tips which can be easily identified both dry and wet.The fourth grouping of fibers is referred to as Generation 4. The fibers for these brushes came from the cosmetic fiber industry but were among the highest of the line fibers available from the industry. Like Generation 3 fibers, these fibers have improved channeling and patterns in the micro level that allow more water to be held but not nearly as much as naturals that absorb water. Like Generation 3 fibers, these fibers are very pliable and soft a the tips both when wet and when dry. Here is the big difference, unlike Generation 3 fibers where their is a very high definition of the tip, Generation 4 fibers tend to be more blunted at the tip which provides a more velvet feel. This velvet feel can be detected both in dry and wet and provide an ultra soft feeling almost like a velvet blanket as opposed to more definitive tip point feel of Generation 3 fibers. So the hallmarks of Generation 4 fibers is fiber that mimics natural hair much more than Generation 1 or 2 in terms of pliability, better control of water application, but much more of a velvet or super soft feeling at the tips.If fibers were harder than Generation 1 they would be defined as Steel Wire and if fibers were any softer than Generation 4, which to some peoples senses would become more like mush, it would be described in terms of a sponge versus fiber tips. A visual aid will be provided in a later section of this article to provide further clarification.Issue 4: What about coloration of the fibers? Does that effect the Generational model? Would there be new classifications for color variations.Clarification: Remember that the Generations are based on a class of synthetic fibers or a grouping with a given set of parameters for feel when dry to the skin, feel when wet to the skin, and overall fiber technology used. So color variation of the fiber has absolutely no impact on the Generation classing nor should it in the future.Issue 5: Higher numbers for the Generational count always equal better brushes.Clarification: Not so. The Generation method only takes into account what class of fiber is used. That is one component, but only one component, of making a brush that works. Here are some equally critical issues that affect how well a brush is liked or disliked by individuals.A. Loft - Loft plays a very critical role in Synthetics fiber brushes since the fibers are thicker and stronger than natural hairs. Synthetics tend to need more loft to allow for the stronger fiber to flex and bend to produce splay. The loft of a Synthetics fiber brush to match an equivalent Badger brush would require an increase in length. A good rule of thumb (but on that is affected by diameter of the fiber as discussed next) is from 4-6% longer for small to medium knot size brushes to 7-10% for very large knot size brushes to accommodate for all around performance of both face and bowl lathering. Example a 20 mm Badger knot with a 50 mm loft would need to be around 52 mm to provide additional bend and flex to make the brush more efficient and more similar to the natural in all around performance. A 26 mm Badger knot with a 50 mm loft would need to have around 54 - 56 mm for a synthetic to provide additional bend and flex to make the brush more efficient, and more similar to the natural in all around performance. Again this discussion centers around not making an overwhelmingly, short loft brush tuned for face lathering, or making an overwhelmingly long loft brush tuned for bowl lathering and paintbrush strokes, but an all around solid performer. This guideline has come from years of collective experience, from the team that first pursued a detailed synthetic brush testing, and also from experience power users who have provide information in detailed reviews on various forums.B. Fiber Thickness or Diameter- Although Synthetics tend to be thicker than natural hairs some manufacturers have chosen to select thinner fibers which can allow for shorter loft due to the additional flex that a very thin fiber can bring. If the fiber is thin enough but still strong enough, the loft can match fairly closely to a natural. That would allow the manufacturer to need less of a measurement adjustment as discussed previously. An example of a thin fiber is the Generation 3 fiber used in the Plisson Synthetic. Many users actually prefer this brush because the thinner fibers allow for more flex and a more closer match to natural hairs. The drawback to thinner fibers is that the brush can become more floppy, and can become more of an issue for those wanting greater backbone. So fiber thickness is another tradeoff that is available to the manufacturer in the brush making process.C. Knot Size and Density - This holds true for both Naturals and Synthetics. The denser the knot is packed with fibers even with a small sized knot makes a big difference in how a brush handles. Some users like a sparser knot to allow more flexibility and others like a denser knot that has more backbone The size of knot can amplify or diminish how the fiber reacts with the skin and in lather generation.D. Glue Bump extended outside the handle versus No Bump extension - This can make a difference in how much a brush flairs out or stays tight. Since a Synthetic fiber cannot take on water and warp, or bloom, like a Natural fiber, a Glue Bump if properly used and shaped can mimic the flaring that would occur under a Natural that has bloomed creating a more sparse and spread out knot. If used improperly it simply shortens the effective loft of the brush and nothing more. If the Glue Bump is kept below the handle opening (not extended) then the brush will seem more tightly packed throughout and will tend to have more backbone. Each method can work to create a stellar brush or a subpar brush depending upon the skills of the manufacturer.E: Shape and Manufacturing Techniques - This simply means that knots can have the following shapes, Bulb, Hybrid (Bulb/Fan), Fan, Flat Top. As with Naturals, the shape will cause different interactions with the skin of the user. The preference of shape is very subjective to the user and makes a difference in how the fibers feel to the user. Manufacturing Techniques have to do with the method of knot construction whether it is hand made or machine made. Hand made knots provide a higher application of skill and craftsmanship and machine made knots provide uniformity and usually a lower cost to produce and perhaps lower price to the consumer. Again another set of tradeoffs that is available to the manufacturer in the brush making process.F. Handle shape and materials - The handle and the materials used, how deeply the knot is seated, and the ergonomics (center of gravity, weight, size, shape) can all play additional roles in how well the brush is make in the mind of the user. These are more set of tradeoffs that is available to the manufacturer in the brush making process.All these items can have large affects on the success of a brush regardless of the type of fibers used. So a well made brush using Generation 3 fibers could for many users outperform a not so well made brush using Generation 3 fibers. In addition manufacturers that have spent more time and have produced more brushes will have an advantage in experimentation of all the subsets under issue number 3 and number 5. This provides more opportunities to currently produce better Synthetic brushes with greater variety since they have gone down the product improvement cycle than those companies with less experience in Synthetic brush manufacturing.For additional information a chart has been developed showing the Generations and some, but not and exhaustive list of the brushes that fit in each category. That chart can be seen here and the continuum line and listing helps to define why only four categories will exist.