Silicon Rubber and Fabric

This page represents a step in the making of a small, homemade, internal concrete vibrator on-the-cheap. Even if you're not interested in making the vibrator this page hopefully demonstrates some approaches to working with common materials in ways that may perhaps give you some ideas that will allow you to boot-strap the technique to fit your own particular project(s).

This sequence of images demonstrates a number of points: 1) mixing silicon rubber and mineral spirits; 2) using the mix to "rubberize" cloth; and 3) forming that rubberized cloth into a sleeve that will later be used as part of a concrete vibrator.

This work is a bit "fumy", so work in an area that has plenty of ventilation. A respirator with charcoal filters isn't a bad idea either.

Pour a little paint thinner into the mixing bowl...not much...maybe 1/8 to 1/4 inch for what we're doing here. I often tilt the mixing bowl so the paint thinner collects to one side and provides a little "depth" to the liquid.

Squirt some caulking into the paint thinner until the level of overlapping beads of caulking begin to "poke through" the surface of the thinner.

Start stirring with the knife. At first it will just seem like a god-awful mess, but within maybe 10-15 seconds you'll notice the caulking beginning to dissolve.

Keep stirring until you feel everything is throughly mixed...maybe a couple of minutes. Just eye-ball it.

Spread some of the mix onto the cloth and work it into the fabric.

Once you've got some rubber spread over the cloth and have worked it into the weave of the fabric, place the PVC tube at the edge of the cloth and just start rolling it up. I press down a little to keep some of the excess rubber from accumulating between the fabric layers.

Once rolled up, take some of the rubber still in the mixing bowl and add a little thickness to the exterior. Its a little like spreading cake icing, so if you wind up with "ridges" don't worry. After the rubber has "skinned over" ever so slightly, put some saliva on your finger (water will work, but spit works best) and smooth down the ridges by gently gliding your finger tip over the rubber. You will probably have to keep lubricating your finger, so sometimes I spit in a small bowl so I don't have to keep spitting directly on my finger or sticking my finger in my mouth (probably not the most sanitary operation).

A final note here: prior to doing all this, find a block of wood and drive a nail into it. This gives you something to slip the tube over so that it can remain upright while the rubber cures. You don't want to ruin the finish by having to lay the tube down on a flat surface while the rubber is still tacky.