On 5/28/2020 at 9:18 PM, jimb0 said:Additionally, carbonating a half bottle means there's a much bigger head space of compressible air to fill, which means you could potentially fit much more CO2 into the bottle that's only partially filled with liquid..
Bingo. Soda Streams are designed to carbonate bottles that are filled to the fill line. Underfilled bottles are liable to overcarbonate.