Cartier and Wayne.....
Okay, you are right. I have to up my press weights.
Below are two responses concerning this subject that I got from another site. They both agree exactly with what you have been saying and one is from Jim at New England cheesemaking supply:
I just sent a message to Jim Wallace, who provides “technical support” for Ricki Carroll. Here is his response regarding the pressing instructions in her recipes:
“the recipe weights are dead weights on our 4” molds .. if you make a larger cheese increase the weight proportionate to the surface area”
Here is the second response from a fellow cheesemaker:
The physicist side of me is compelled to speak.
It is important to understand the fundamental difference between Force and Pressure. What we measure and call Weight is a certain type of Force, specifically, it is m*g where m is the mass of the object and g is the acceleration of gravity (often casually, but incorrectly called the “force of gravity”). Here in the U.S. we most commonly measure weight in pounds and ounces. Pressure is Force/Area, and we most commonly measure this in units of pounds per square inch, or psi. Rick’s examples above are spot on regarding the change in pressure when the surface area increases.
I believe it is correct that the weight required for pressing does increase proportional to the surface area of the cheese. There is a certain amont of force that is required to expel whey and knit the curds together for a particular cheese, and it is the distributed force, i.e., the pressure that is actually “felt” in the cheese (if you could imagine yourself inside the cheese.) It can be helpful to imagine an extreme case, for example a 4 in wheel vs. a 12 in wheel with a 50 lb weight applying pressure to the wheel. I suspect the thickness of the cheese may also be a factor, and I have a feeling this topic is probably covered in some of the more technical (and expensive) cheese making texts that I have not yet purchased.
If you are looking for a more personal experience, try the following: Take off your shoes, and stand on a solid floor. For most people, the pressure on the soles of your feet is somewhere in the range of 1-2 psi (it is your weight divided by the surface area of your feet.) Now find a small object, preferably between 1 and 2 inches in its largest dimension, and put it under one heel. If you lift up the other foot, and try to put all of your weight (FORCE) on that heel with the small object under it, I can almost guarantee it will hurt. Same FORCE, greater PRESSURE.
The reason the plastic followers that come with many cheese molds have the raised circle on the backside is to help distribute the force uniformly over the follower. The plastic follower, if pressed in the center, will flex more than a metal or wood follower which is stiffer. By pressing on the ring it helps distribute the force more evenly between the center and the edge. It also makes it easier to keep the follower level.
Thanks for all of the information you gave me concerning this subject.
I should have just listened to you guys from the first. It would have saved a lot of typing. :-)