Instead of adding boiling water to your substrate, just boil the substrate. I’ve had no issues with contam using this method.

Not to discourage you, but this is likely counter-productive. I've read a few papers on contamination in substrate (I'll link one focused on Trichoderma spp at the bottom), and one of them concluded that sterilization was worse than pasteurization, and doing nothing was actually better than sterilization. Their theory behind this was that sterilization also killed bacterial competitors for Trichoderma spp, allowing it to flourish without competition. Their sterilization technique was 121C (around 250F), so you may not be approaching that, but you're definitely much higher than the 60 and 80C pasteurization used in the paper. - Here is the paper. This is why it's suggested to put your substrate in an oven around 180F after pouring boiling water over it, rather than just boil it awhile on the stove. Fungal spores can be much hardier than bacterial spores, so you end up killing basically everything besides the Trichoderma.

/r/unclebens Thread Link -