Weight or PSI when pressing cheese

[hinkensj]

My apologies for bothering you cheese pros with a newb question, but I can't seem to find good information on the web concerning the amount of weight to add to my press.

Recipes state something like 8 pounds form1 hour. Does this really mean 8 PSI on the cheese? So for a 6" diameter mold (roughly 28 sq in) would I place an 8 pound weight on top or a 8*28= 224 lb weight. And as I type this 224 pounds seems quite excessive.

The CulturesForHealth.com website says the weight stated in recipes is PSI, but every recipe simply states pounds.

Seems there would be some relationship between the diameter of a press and the required weight...

Thank you for helping.

 

[passedpawn]

Most recipes call for pounds weight, and then specify the diameter of the mould required. Thus, they are implying PSI. If you use a different mould, you'll need to figure out what PSI was intended, then recalculate the pounds pressure based on your diameter. Logical people would assume it would be better just to specify PSI, but cheesemakers aren't always good at math and physics.

If you're given a recipe that includes Pounds_1 and mould Diameter_1, and your mould is Diameter_2, and you wonder what Pounds_2 should be...

An easy way to convert is Pounds_2 = Area_2 * (Pounds_1 / Area_1 )

BTW, in case it's not obvious

PSI = Pounds / sq.in. The square inches is the 3.14 * the radius squared.

 

[hinkensj]

Thanks passedpawn. Exactly what I was looking for. In fact the recipe specifies an 8" press and I am using a 6" so a conversion will be necessary. The math I can handle, filling in the blanks in a recipe, not so much...

Thanks again.

 

[hinkensj]

In case others read this thread it should be pointed out that the area of a circle is the radius squared times 3.14 not pi times the diameter as mentioned by passedpawn. He inadvertently listed the circumference of a circle instead of the area.

So the conversion in the above example should be Pounds_2 = Pounds_1 * (Radius_2 / Radius_1)^2

I'm not misinterpreting what you are saying, am I passedpawn?

 

[lump42]

In case others read this thread it should be pointed out that the area of a circle is the radius squared times 3.14 not pi times the diameter as mentioned by passedpawn. He inadvertently listed the circumference of a circle instead of the area.

So the conversion in the above example should be Pounds_2 = Pounds_1 * (Radius_2 / Radius_1)^2

I'm not misinterpreting what you are saying, am I passedpawn?

If it is implied a set amount of PSI on the curds, then I would use the pounds and area (sq in) in the conversion formula instead.

Pounds_2 = Area_2 * (Pounds_1 / Area_1 )

You'll get a different amount of weight if you use the diameter or radius instead.

 

[passedpawn]

In case others read this thread it should be pointed out that the area of a circle is the radius squared times 3.14 not pi times the diameter as mentioned by passedpawn. He inadvertently listed the circumference of a circle instead of the area.

So the conversion in the above example should be Pounds_2 = Pounds_1 * (Radius_2 / Radius_1)^2

I'm not misinterpreting what you are saying, am I passedpawn?

WOOPS!!! You're right. I'm perty good at math, too, but you wouldn't have guessed that. I'll fix my post above so there will be no further confusion in the future. Thanks for that.

 

[passedpawn]

If it is implied a set amount of PSI on the curds, then I would use the pounds and area (sq in) in the conversion formula instead.

Pounds_2 = Area_2 * (Pounds_1 / Area_1 )

You'll get a different amount of weight if you use the diameter or radius instead.

You're right too. I am an idiot today. My wife was rushing me out the door. I'll fix what I put up above. I swear I'm not even drinking (yet)

 

[hinkensj]

Both of the above equations are right. When using Area_2 / Area_1 as lump42 suggested, there is pi in the numerator and the denominator so they cancel. Using the square of the ratio of the radii eliminates the need to calculate the areas.