The objective of this post is to share some experience and perspective, not to advance dogma or prescribe what anyone else should consider best with regard to knot specifications.
Loft is the vertical distance from the top of a handle where the knot is inserted into the socket (i.e., knot hole) to the highest point of the knot at its crown. It is the most common, and often the only, measurement given in description of a brushs knot besides diameter at the insertion point, which more accurately states the capacity of a particular handle than it does the size of a knot set into that handle. Consider a knot with a diameter of 23.5 mm where the glue at the circumference of its base meets the hair. Such a knot might be set into either a 24 mm, or a 25 mm, or possibly even a 26 mm socket. But, although its characteristics (splay, volume density, etc.) can be altered depending on the selected socket size just as those characteristics can be affected by loft the actual size of the knot doesnt change.
Several variables can affect the appearance, feel, and performance of a knot. Those include: 1) hair type and quality (e.g., softness, resilience), 2) base diameter (measured at the top of the glue plug), 3) volume density at its base, 4) shape, 5) depth of set, 6) loft, and 7) free loft (the vertical distance from the highest level glue reaches at the center of a knot to the knots crown). All of these factors in combination influence set-shape (i.e., shape as set in the handle), overall aesthetics, bloom, splay, effective (volume) density, backbone, scrub, scritch, floppiness, moppiness, lather production, lather uptake, flow-through, and drying time. Loft measurement, by itself, is a very incomplete specification.
Heres an example. The brush shown below has a 28 mm socket. I didnt set the knot, so I dont know its base diameter. The loft is just shy of 54 mm (in fact my calipers still brush a few hairs at 54 mm). Some users wouldnt consider buying a brush lofted that high for fear of flop. But guess what the knots free loft is.
Answer:
That doesnt mean its a bad brush. I tried one like it and was surprised to find that it wasnt harshly scrubby at all, at least not for me. My guess is that's due in significant part to the fact that, given the 12.5 glue bump (54 mm 41.5 mm), the knot was probably set very high in the socket, which tends to allow more splay, which in turn reduces volume density (because the same number of hairs are spread across a larger area). But still, if I were spending over $200 on a brush, Id probably want to know whether 54 mm of loft was going to come with 41.5 mm of free loft or 48-50 mm. Thats a very significant difference. All else being equal, Id expect a brush lofted at 54 mm, but with a 12.5 glue bump, to have more backbone and scrub than one with loft of 50 mm and free loft of 47 mm.
Im admittedly a brush nut. When I first fell into fascination with brushes, I bought over 30 of them in three months. My purpose wasnt to collect; it was to figure them out for myself and, hopefully, discover what I liked most. That said, I didnt and dont decide what I like based on analysis. I know what I like based on what I select to use. Its as simple as that. Many times Ive gone to the cabinet with an intent to take out a brush that hadnt been getting due attention and then at the last moment grasped the one I had used just the day before, and the day before that.
Finding what you like can be a challenge. But recognizing it when you finally experience it is absolutely not rocket science. For some of us, however, discovering what we like stimulates a quest to understand why we like it, what accounts for a particular brush turning out to be a favorite, and (most important) how we can prospectively identify another one (i.e., without first having to buy and try a dozen or more). That doesnt involve rocket science either, but its also not entirely straightforward and simple.
What follows is more-or-less a photo-essay that shows how I approach setting knots. It focuses on a comparison of two knots of the same nominal grade, both of which were obtained as part of the same order from the same Chinese supplier.
The photo below shows the two knots side-by-side along with some stuff I use in setting knots. Note the socket spacers ranging in thickness from 5 mm to 10 mm. They allow easy comparison and selection of potential loft settings. Note also the gauge we made for use in measuring free loft. I included some handles in this photo because, in my view, different knots match better with different handles, and different handles may want different lofts. Its a little like feng shui.
Here are just the two knots (hanging out in front of a brick). Both were designated for use in handles with 26 mm sockets. The one on the left (L-type) is about 68 mm tall and has a base diameter of approximately 24.2 mm. The knot on the right (S-type) is barely over 63 mm tall with a base diameter of about 25.2. Note that the L-type knot is glued in the lower, light-colored band (2-band hair actually has three distinct bands, at least before it is cut), whereas the S-type knot is for the most part glued at the bottom of the dark, middle band. More hair can be packed into a given circumference in the lower section than the dark, middle section. This accounts for the fact the L-type knot shown here, despite its smaller base diameter, is a slightly tighter fit in a 26 mm socket than the S-type knot.
The L-type knots free loft is about 47.5 mm. (The gauge rose a bit in the knot when I removed my hand to take the photo.)
Heres the L-type knot set at 48 mm. I hate the appearance, and Im pretty sure Id hate the way it would feel in use. But some might love it, and theres nothing wrong with either bias.
Below is the same knot set at a loft of 50 mm. I still wouldnt go for this myself.
Heres 52 mm.
And now below is the S-type knot with free loft of about 45 mm.
This is the S-type knot set at 48 mm, which wouldnt be my first choice, but I think I could enjoy this brush.
Here is 50 mm.
And finally, 52 mm.
The L-type knot differs in appearance from the S-type at a given loft due to the facts 1) it has to be sunk deeper in the socket, 2) its glue bump is therefor positioned differently in relation to the socket rim, 3) it has more free loft (independent of overall loft), and 4) it probably has slightly more area density at the socket rim.
There was a time when I thought a 24-26 mm brush wanted 49-51 mm loft. Now I would say it depends.
Loft is the vertical distance from the top of a handle where the knot is inserted into the socket (i.e., knot hole) to the highest point of the knot at its crown. It is the most common, and often the only, measurement given in description of a brushs knot besides diameter at the insertion point, which more accurately states the capacity of a particular handle than it does the size of a knot set into that handle. Consider a knot with a diameter of 23.5 mm where the glue at the circumference of its base meets the hair. Such a knot might be set into either a 24 mm, or a 25 mm, or possibly even a 26 mm socket. But, although its characteristics (splay, volume density, etc.) can be altered depending on the selected socket size just as those characteristics can be affected by loft the actual size of the knot doesnt change.
Several variables can affect the appearance, feel, and performance of a knot. Those include: 1) hair type and quality (e.g., softness, resilience), 2) base diameter (measured at the top of the glue plug), 3) volume density at its base, 4) shape, 5) depth of set, 6) loft, and 7) free loft (the vertical distance from the highest level glue reaches at the center of a knot to the knots crown). All of these factors in combination influence set-shape (i.e., shape as set in the handle), overall aesthetics, bloom, splay, effective (volume) density, backbone, scrub, scritch, floppiness, moppiness, lather production, lather uptake, flow-through, and drying time. Loft measurement, by itself, is a very incomplete specification.
Heres an example. The brush shown below has a 28 mm socket. I didnt set the knot, so I dont know its base diameter. The loft is just shy of 54 mm (in fact my calipers still brush a few hairs at 54 mm). Some users wouldnt consider buying a brush lofted that high for fear of flop. But guess what the knots free loft is.
Answer:
About 41.5 mm, stretching.
Im admittedly a brush nut. When I first fell into fascination with brushes, I bought over 30 of them in three months. My purpose wasnt to collect; it was to figure them out for myself and, hopefully, discover what I liked most. That said, I didnt and dont decide what I like based on analysis. I know what I like based on what I select to use. Its as simple as that. Many times Ive gone to the cabinet with an intent to take out a brush that hadnt been getting due attention and then at the last moment grasped the one I had used just the day before, and the day before that.
Finding what you like can be a challenge. But recognizing it when you finally experience it is absolutely not rocket science. For some of us, however, discovering what we like stimulates a quest to understand why we like it, what accounts for a particular brush turning out to be a favorite, and (most important) how we can prospectively identify another one (i.e., without first having to buy and try a dozen or more). That doesnt involve rocket science either, but its also not entirely straightforward and simple.
What follows is more-or-less a photo-essay that shows how I approach setting knots. It focuses on a comparison of two knots of the same nominal grade, both of which were obtained as part of the same order from the same Chinese supplier.
The photo below shows the two knots side-by-side along with some stuff I use in setting knots. Note the socket spacers ranging in thickness from 5 mm to 10 mm. They allow easy comparison and selection of potential loft settings. Note also the gauge we made for use in measuring free loft. I included some handles in this photo because, in my view, different knots match better with different handles, and different handles may want different lofts. Its a little like feng shui.
Here are just the two knots (hanging out in front of a brick). Both were designated for use in handles with 26 mm sockets. The one on the left (L-type) is about 68 mm tall and has a base diameter of approximately 24.2 mm. The knot on the right (S-type) is barely over 63 mm tall with a base diameter of about 25.2. Note that the L-type knot is glued in the lower, light-colored band (2-band hair actually has three distinct bands, at least before it is cut), whereas the S-type knot is for the most part glued at the bottom of the dark, middle band. More hair can be packed into a given circumference in the lower section than the dark, middle section. This accounts for the fact the L-type knot shown here, despite its smaller base diameter, is a slightly tighter fit in a 26 mm socket than the S-type knot.
The L-type knots free loft is about 47.5 mm. (The gauge rose a bit in the knot when I removed my hand to take the photo.)
Heres the L-type knot set at 48 mm. I hate the appearance, and Im pretty sure Id hate the way it would feel in use. But some might love it, and theres nothing wrong with either bias.
Below is the same knot set at a loft of 50 mm. I still wouldnt go for this myself.
Heres 52 mm.
And now below is the S-type knot with free loft of about 45 mm.
This is the S-type knot set at 48 mm, which wouldnt be my first choice, but I think I could enjoy this brush.
Here is 50 mm.
And finally, 52 mm.
The L-type knot differs in appearance from the S-type at a given loft due to the facts 1) it has to be sunk deeper in the socket, 2) its glue bump is therefor positioned differently in relation to the socket rim, 3) it has more free loft (independent of overall loft), and 4) it probably has slightly more area density at the socket rim.
There was a time when I thought a 24-26 mm brush wanted 49-51 mm loft. Now I would say it depends.