There is a lot of discussion here in the forums about the topic of pressure.
Here is a summary of mine. Apologies ahead of time of this is review for anyone.
Most recipes call for 10lbs or 20lbs or whatever to be placed on the curds. Any discussion of "pounds" is a discussion of weight. This is a measure of force. Also, most recipes were (At least in the Rikki Carrol book) were written for moulds of 4 inches in diameter. So if you want to use a larger diameter mould, you will need to adjust the force. I have adapted my recipes to use pressure, not force. Pressure is merely an expression of that force over the area it is pressing on.
So, if Rikki's book calls for a 10lbs weight, that really means .8psi.
How do i get that?
Assuming we have a mould of 4inches in diameter, that gives us 12.5 square inches. (A=PI*R^2) that is 3.1415*(2*2)
So, 10lbs spread over 12.5 square inches of cheese is about .8 pounds of force per square inch.
So what does that mean?
To me, what that means is that if you elect to use a 6in mould instead of a 4in mould, and want to use the same recipe, you will want to maintain that same force (.8lbs) per square inch.
Example:
So if you have a 6 inch mould, It has 28.27 square inches of surface area pressing on the cheese. If you want to maintain that same .8 pounds of force per square inch, you will need to push down with more force, in this case 22.6 lbs instead of the original 10 lbs
So even though you are using more down force (weight), the same the same pounds per square inch of force is being applied to your cheese.
Carter has worked out a great table of actual numbers somewhere.