A friend, John, had just built himself a bouldering wall in his garage to train on and keep his fitness up. He scored a box of secondhand climbing holds from an indoor climbing gym. Although they were used, they were still fairly expensive. So we set about making our own using the ones he had as templates.
The first step is to make a mold from an existing hold. There are two approaches, both with their pros and cons. The ‘correct’ way is to use mold-making silicone. This provides a flexible and reusable mold, but silicone is expensive. The approach we went with was to use clay. The drawback with this method being that you destroy the mold every time you use it.
Carefully remove the existing hold once the impression is made. Next roll some clay to make the recess for the bolt head to sit in, place it in the mold and put a washer on top. To form the tube where the bolt will eventually sit I used McDonalds drinking straws.
Next it’s time to mix up the resin. This is made from polyester resin, sand and coloured with powder paint (you know, the stuff that children paint posters with).
This then gets poured into the clay molds. Here I found another drawback of clay: it’s full of moisture which is slowly evaporating. This cools the epoxy and can make curing times very long (24hrs). If you make a mold out of silicon or thermoplastic then you can heat your holds as they cure (I used a cardboard box and a fan heater when using a non-clay mold) and you can punch out a batch of fully cured holds in 1hr! Clay is excellent for a proof of concept, but you’d want to find a better method to fill a whole bouldering area.
Once the holds are fully cured they can be stripped out of their molds. These holds are very strong, but can be brittle so it’s very important that before you tighten them to the wall of your bouldering area that the backs of them are perfectly flat. No matter how carefully you pour them you will not get them totally flat and this seemed like it might be quite a challenging process to flatten them after curing. But John came up with a wonderfully simple solution – rub them on an abrasive flat surface… like a road!
And when they’re done they look just like the one below. They’re just like the ones you’re used to using in the gym and exceptionally cheap to make! And if you take an impression of all your holds, you double your collection every time you do a pour.