Shaving Brush Hairs material, black fray when clustered

I finished an Architectural Visualization, a bathroom scene.

Having finished the design (enough archviz for the presentation of the essence of the space), I decided to play around some with more detail, that had intrigued me during the “decoration” the scene.
Blowing an area I improved several materials but could not get rid of a problem rendering the shaving brush:

The hairs are modeled on faces shaped like paper strips mounted and pivoted at the base. Each strip has a mask of several hairs on it, when the mask is applied each strip becomes an array of hairs. The clip below shows one face in edit mode and next to it the material preview

I could not get rid of a fray of black at the of the brush, by toying with values

I have thought of more complicated solutions, like maybe apply a gradient transparency from top to bottom.
But before I get into that I wonder if I’m missing something? if it can be done simply.

Here is the blend file (size 190MB)

PS: surprisingly when you look at a shaving brush in real life, it does a little bit of this, I assume the light trapped between hairs, gives a little “pepper” effect, but less intense than the render and not at the same viewing angles, not in the same way.

Hello! That looks like you need to increase the transparency bounces in cycles settings. With that amount of layers you’re going to need a high number to let the light go through all of them. I would suggest to use hair particles instead to avoid this situation.

I’ll try the bounced in a little while, yet
Wouldn’t light bouncing off hair have the same problem?

Not really unless you add transparency to it, but since the hair already has the right shape (thinner tips), you shouldn’t do it.

This has 24 passes (up from 4)… still a few black specs in the back… not worth it to re-render for my purposes

Can’t you just increase the depth and box render a small area, mix in in in post?