Filling a Hollow Handle

I need to fill a brush handle before installing a knot, and I'd like advice on what to fill it with. Here's the situation:

I had an old Ever Ready 100, but its hair was exhibiting Boar Pattern Baldness, so I decided to redo the knot. This is my first attempt at a brush refurbishment. I was able to steam the old knot out, and it came out pretty neatly with its adhesive plug. No drilling or dremeling required. Hooray!

I discovered underneath the old knot, however, a completely hollow handle. The hole is 2 inches deep, 20mm wide at the opening, and has the contours of the handle, which is just a thin acrylic shell on a base. I want to build that hollow up with something before installing a new knot. The total volume is about 20 ml, or just short of 1/8 cup, so I'm looking at about 15 ml of fill, leaving enough space for the base of the knot and adhesive.

What should I fill it with? The fill needs to be water proof, support the knot, not make the base so heavy as to disturb the balance of the finished brush, and semi-liquid going in so it fills the hollow before drying hard with a flattish top. Three things I have around the garage that occurred to me are wood putty, silicone caulk, and Gorilla Glue. I also thought about inserting a 3/4" x 1 1/4" length of wooden dowel into a liquid adhesive filler medium.

Your thoughts? Any advice would be gratefully received.

On the first one I did. I filled with pennies and epoxy to the level that I wanted the knot. Let set up, than installed the knot. I did not fill it al the way with pennies, just to the weight that I though that I would like. I used a horse hair knot, not so sure I like it. is a little floppy for my taste.

Pretty much anything can be used. I drop in a neodymium magnet so I can magnetically hang it. Then seal in some lead for weight and use a cork to fill space and provide a shelf for the knot.

Silicone.

Epoxy.

Either you can add fishing weights or pennies to and get a little heft. Be careful with epoxy though it could get rather hot when cutting.

I have filled in old handles with silicone caulk and it seems to do well. It takes a bit of tapping and I went in a few layers to allow it to set, but I wasn't in any hurry.

[MENTION=81056]JimL911[/MENTION] is right.

A magnet in the very bottom is very cool.

I've done this before too.

I don't recommend using silicone as it will expand when heated and could cause the handle to crack. Learned that the hard way after leaving a restored brush to dry on the bathroom window. I use plastic beads which can be found at the craft store (used for bean bags or stuffed animals) or have also used hot glue. Many members have used cork which I think is a good method but I have never tried it.

Thanks.

Never thought of expansion. Great tip.

I mostly use epoxy, but don't use a fast drying type or the heat at that volume may distort the handle. It may help to do it in a few applications.

I also use some coins to add heft and and help with spacing the knot where I want it. Too may coins and it will be heavier than desirable so be careful. I have seen where some have used plastic balls roughly the size of BBs in a bed of epoxy.

I really appreciate all the advice. Many thanks to all. I'll wait until my knot arrives from TGN to do any further work so I can get the depth right. The opening is 20mm, so I'm hoping my 18mm knot has enough diameter. It's only 2mm of space, but that's 10% on a brush this size.

Hot glue and pennies here. Some guys use nuts. I like the magnet idea. That's a good one.

Anyone ever tried FastSet 20? Or any other wallboard compounds? I know they're hot-set compounds, which can get really hot in large quantities, but I wouldn't think a few tablespoons would be capable of getting hot enough to damage the rubber or plastic.

I have a Maestro handle I'm about to mount a TGN silvertip in. I chipped out a good bit of the old plaster of paris in the handle in the process of removing the old boar knot. I don't have any plaster of paris, but I do have fast set.

Also, anyone ever use liquid nails to set the knot? I have a caulk tube of liquid nails for kitchen and bathroom use. Supposed to be fully waterproof, and it's doing a fantastic job right now of holding my base trim to the fiberglass tub in my son's bathroom. My son somehow floods the floor in front of the tub regularly, and the glue is still holding on like iron.

I guess I'll probably just try it, unless someone has a strong warning against. Worst case, I destroy the handle with the fast set. I have 3 more vintage brushes with bad knots to play with...

If the glue gives up, I just chip it out and reglue the knot with an epoxy...

I use some coins and epoxy. So far, no issues.

I have a couple restores planned and I am going to try either steel or lead shot from shotgun shells and top with marine epoxy.