Rendering the beeswax is basically filtering/cleaning it, to make sure all the leftover honey and dead bees are separated from the wax. The beeswax melts and drains into the pot while the other stuff stays in the cloth.
In class, we filled the muslins with as much beeswax as possible and tied it up into a little sack. Whaea Leanne lent us her pot which she uses for rendering beeswax and some muslin cloth. We went to the staff room to use the stove. Luckily, there was another teacher working in the staff room at the time, so we still had some supervision. Before Whaea Leanne left, she told us how to render the beeswax.
First, we filled the pot with cold water, and turned the heat up to just above medium. We prodded the beeswax with a popsicle stick to help squeeze the wax out. We took shifts (10 minutes for each of us) to prod it, and watch over it so when it started to boil we could quickly turn the heat down very low. Beeswax is highly flammable, so as soon as it started to boil we needed to lower the heat otherwise it would burst into flames.
Fun Fact! The saying "mind your own beeswax" comes from rendering beeswax because if you look at someone else's beeswax, yours might burst into flames.
After around 40 minutes, the beeswax had drained out and the 'sack' was very thin. There was also a lot of beeswax sitting on the surface of the water. We used the popsicle stick to squeeze the very last bits out, and then we put the muslin into the now-empty ice cream container, to throw it away.
Finally, we needed to let it cool overnight. To see how it cools and hardens, Whaea Leanne did an experiment. We got another empty ice cream container and put in a bit of cold water. Then we poured a tiny bit of the liquid wax in. Because of the cold water, the wax immediately cooled down and hardened. After that cool experiment, we left the pot of wax to cool in the staff room, which Whaea Leanne took back to class the next day.
We repeated this process twice so we had enough beeswax for the many pieces of fabric.