I wanted to render the fat from some bacon to produce bacon grease. The usual advice that you see on the internet is to simply fry whole strips of bacon at a low heat, for a longer period, and the fat will melt away from the meat proper. That normally works for me.
The other day I wanted to try someting different. I have previously rendered other fats in different ways. I've tried a 'wet render', by simmering at a very low temperature in water. That worked well for lamb fat. And I tried a 'dry render' by putting the fat in the oven at a lowish temperature (gas mark 3 = 160C), which worked well for chicken skin.
I tried these methods with some bacon fat, that I had cut off from the meat of back bacon strips. So it was just 16 white strips of cold fat. But they didn't work. With the wet render, no matter how long I simmered for, the water didn't get more than a tiny bit oily. The dry render behaved similarly, except that it did give a tiny bit of fat, but nearly all of the fat was still whole, the bits hadn't reduced in size at all after I baked for about 5 hours.
Why didn't it work? At first I thought the temperature might be too high, but it's not like the bits were getting blackened or anything. And surely a higher temperature would also show signs of rendering the fat, it wouldn't just arrest the entire process.