I found this thread interesting and informative.... I know it is out of date, but I thought I could add a useful piece of information for people to ponder.... There is very little air inside a cheese that is being pressed.... The material is either liquids or solids, both of which are incompressible.... The combination acts to deform in a plastic manner, ie it flows to fill the shape of the container (mould), and the solids are retained by the mould and cheesecloth, while the liquid (whey) can drain out through the holes....This reduces the volume over time, which is why you have to retighten the springs on a spring style press once in a while, as the height of the cheese gets smaller, the springs decompress, and the pressure drops....
The density of our cheese is a bit under 1, proven by the fact that they float a bit, but for the purpose of this argument, let's consider the cheese to be the same density as water.... A column of water exerts a pressure at the bottom proportional to the depth of the column.... Anyone who is a SCUBA diver will know that works out to about 1 atmosphere (14.7 psi) for each 33 feet of depth.... which is less than 1/2 psi per foot.... or about 0.037 psi per inch of depth.... It seems obvious, then, that the pressure at the bottom of a cheese will be about 0.037 psi greater per inch of depth than it is at the follower, and in the middle of the cheese about half that difference....
If we are pressing at 1 psi (based on the follower area), with a 3" deep cheese, the pressure at the bottom will be about (3 x 0.37) = 0.111 psi greater than at the top (actually a bit less, because cheese is lighter than water).... Call it 0.1 psi greater at 1 psi.... However, you flip the cheese during the pressing process, so the average pressure (over time) is only 1.05 psi.... Double the pressing force, the average pressure is 2.05 psi instead of the 2.0 you are applying.... At 5 psi, with a 3" thick cheese, the average pressure is only 1% more than what you think you are applying....
If you ever wondered why when you first apply very light pressure, the curds at the top are not knitted as well as those at the bottom, particularly on a tall cheese, there is your answer.... Correspondingly, at higher pressures, the height of the cheese (for home cheesemakers) is insignificant compared to the pressure exerted by the follower.... and the height (aspect ratio) of the mould makes no significant difference on a hard cheese....
As to why a tall, moist cheese may "slump", and expand at the bottom during air drying, this also provides your answer.... The weight of the upper part causes pressure on the lower part, stretching the rind outwards and causing the bulge.... until you turn it over....
Bob
