How To Use A Chess Press When Changing Recipe Quantities
It is a common occurrence that you find a cheese recipe that you really want to make, but the quantity is just not right for you. Perhaps the recipe calls for 3 gallons of milk and you want to use 2 gallons, or you want to increase it to 4 gallons.
I would advise against using less than 2 gallons for hard cheeses as too much rind would form in ratio to the cheese.
Now, it’s all well and good to change the amounts of all the other ingredients. This works well for both soft and hard cheeses. The real challenge arises when you are changing quantities of a hard cheese recipe and it comes time to press the cheese. How do you use your cheese press to exert the right amount of ‘press’ on your cheese?
If you are not sure about the process of using a cheese press, you can read all about it in this article: How To Press Cheese
Note on cheese molds: As a general guide, I will usually use a 4 inch mold for recipes calling for 2 gallons of milk, and a 5.5 inch mold for 3 gallons.
The Difference Between Weight & Pressure
In my recipes, I always state the amount of weight needed to press a cheese. It is important to note that the weight needed will vary depending on the size of the mold you are using. The factor that will always stay the same is the pressure being applied to your curd when pressing.
So, what is the difference between weight and pressure?
To start off, weight is measured in kilograms (kg) or pounds (lb), whereas pressure is measured in kilograms per square centimeter (kg/cm2), or pounds per square inch (PSI).
What does that mean? Pressure is essentially the weight that is placed on one square cm or square inch of area. The weight needed to achieve this pressure differs based on the area size.
For instance, if you need a PSI of 1, that means that you need 1 pound per square inch of area. So, if you had a mold with 16 square inches of area you would need 16 pounds of weight to achieve a PSI of 1. Whereas if you had a mold with 36 square inches of area you would need 36 pounds of weight to achieve a PSI of 1.
Making sense? Great! Here is a little formula for pressure to help put things into perspective.
Pressure = weight / area
For those of you who skipped math in school, you can work out the area of your mold by squaring the diameter. So if you are using 4 inch mold, the area would be 4 squared, or 4×4 which equals 16 square inches.
Working Out The PSI
Example: We know that a recipe calls for 2 gallons of milk, a 4 inch mold and 8 pounds of weight. The area of the mold would be:
4×4 = 16 square inches.
The PSI formula looks like this:
8 / 16 = 0.5 PSI.
We want to increase the amount of milk used to 3 gallons, which then requires a 5.5 inch mold to be used.
The area of this mold is:
5.5 x 5.5 = 30.25 inches squared.
So now we know that the PSI needed is 0.5 and the area is 30.25 square inches. Using our formula, it looks like this:
0.5 = weight / 30.25
If we flip that around it becomes:
30.25 x 0.5 = weight
So the weight needed for this mold now becomes 15.125 pounds.
Doing The Math The Easy Way
I know what you’re thinking; it seems like a round about way of doing a simple equation. And it is, but I wanted to get to the fundamental aspect of pressing cheese so that you can understand what is actually happening.
Alas, there is a much simpler way to find out what weight you need.
Instead of calculating the PSI, you can pretty much skip that step altogether and use this formula:
Weight = area of new mold / area of original mold x original weight.
In our example above, we are changing a 4 inch mold with an 8 pound weight to a 5.5 inch mold. Inserting the known data into the formula looks like this:
Weight needed = 30.25 / 16 x 8
So in this case we get a new weight of 15.125 pounds.
We can also flip this around if we want to decrease the size of the mold being used.
Example: the recipe calls for 3 gallons of milk, a 5.5 inch mold and 15.125 pounds of pressing weight. We want to change this to 2 gallons of milk using a 4 inch mold. Insert the details into the formula as follows:
Weight needed = 16 / 30.25 x 15.125
As you can see, the weight needed for my 4 inch mold is 8 pounds.
Hopefully this helps you in changing up recipe quantities when making cheeses that need to be pressed. It can be hard to wrap your head around the idea of pressure rather than weight, however by using a simple formula you can tackle conversion challenges quite simply.
If you have any comments or questions regarding cheese pressing, you can head over to the Curd Nerd Forum