Glue Bump and Effective Loft

Posted by Michael Polsinelli on

[caption id="attachment_41" align="alignright" width="232"]
 My thumb is at the top of the epoxy[/caption] I recently came across the term "glue bump" in a post on the Shave My Face forum.  I was oblivious to the term before, but along with knot size, loft, and hair quality, I think it is an important concept to how a brush performs. Basically, the when the epoxy of the knot is above the top of the handle. This effectively shortens the loft making  the brush feel scrubbier (more backbone) than a brush with the same loft and no glue knot. The Shave Nook forum has some great posts that go into detail:  Glue bump, an explanation by Lee of Wet Shaving Products, and Brushology: on glue and bumps by Ken of Dark Holler Design Works. Some people dislike glue bumps, but this is actually a reason why I decided to import the Zenith line. It's not a good or bad trait, but having a glue bump makes it difficult to compare with brushes that don't have one. Some have said that effective knot (from the glue bump to the top of the brush) is a more important measurement to predicting how a brush will perform. I decided to make some comparisons between some brushes that I have at home. I compared my old Zenith, the Zenith B03-A26, the Semogue SOC, and the Omega 48. I used a skewer to measure from the top of the knot to the top of the brush. [caption id="attachment_45" align="alignleft" width="300"]
 Skewer touching the top of glue bump[/caption] [caption id="attachment_46" align="alignleft" width="300"]

 This is how far down the skewer went[/caption]               [caption id="attachment_42" align="alignright" width="233"]

Skewer touching the top of glue bump







his is how far down the skewer went


Old Zenith Brush with a higher glue bump. Old Zenith Brush with a higher glue bump.[/caption]   My old Zenith brush has a very large glue bump. the loft

Old Zenith Brush with a higher glue bump.


measures a little over 65 mm with an effective loft of just over 52mm.  It face lathers well and is my favorite brush.             [caption id="attachment_41" align="alignleft" width="232"] My thumb is at the top of the epoxy[/caption] The aluminum handled Zenith B03-A26: Zenith says that this brush has a loft of 57mm. I measured just over 60mm. The effective loft measured 53 mm. I was actually disappointed to find that the modern brushes had a smaller glue knot than the older ones. Because of the shorter effective loft, I like this knot a little better than the longer Zenith Pro         

Omega 48 with the smallest glue bump



    [caption id="attachment_44" align="alignright" width="279"] Omega 48 with the smallest glue bump[/caption]   I originally thought that my old aluminum handled Zenith was an Omega. When I got it I immediately knew that it was a very different brush. It has the smallest glue bump and longest actual and effective loft measurements. Omega says that it has a 70 mm loft and I get about the same at 69.5 mm. The effective loft is just under 65mm.           [caption id="attachment_43" align="alignleft" width="226"] Surprisingly large glue bump on the Semogue SOC boar.[/caption]   The Semogue was a surprise to me, because I find it the floppiest. I measured it at 53 mm (most places say that it is 55 mm) It has an effective loft of just under 48 mm. This is clearly the shortest loft, both actual and effective, but it performs very differently. It blooms outward unlike the other brushes. I wonder if the bristles are glued at an angle rather than straight upward. Density and bristle thickness will also play a role how much backbone a brush will give. Also, a brush with too much backbone will feel scrubby in a bad way.  I found it interesting that each of these brushes had a glue bump as there are some manufacturers that don't make their knots with glue bumps. Are Zenith brushes better or worse because of their larger glue bumps? No, but the glue bump will affect how the brush performs. In the coming week, I'll be measuring all of my brushes for sale and listing the effective loft height, so that you can have a better idea of what to expect from them.

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