When making yoghurt we recommend using the BPA-free plastic insert as we know that the container fits perfectly inside the yoghurt maker, thus making the space surrounding the container minimal and reduces the chance of temperature fluctuations.
If you are wanting to use a glass container this is something you need to be aware of and you will need to do some experimenting to find out how the process will work with the change of vessel. The thickness of glass and the amount of space surrounding the container you use will be a big factor in determining how your yoghurt turns out. You will need to monitor the temperature while it is fermenting to make sure that it is in the correct temperature range. We would recommend doing a water test to ensure the temperature is correct which you can do by following the same instructions on testing your yoghurt maker which I have linked below.
Some yoghurt makers and websites will suggest putting water around the inner container. This can NOT be done with a Green Living Australia Yoghurt Maker as this can lead to water getting in with the 240-volt electrical circuitry and can be very dangerous.