I made a batch of chicken stock yesterday and cooled it by the method I
described in a prior thread. I place the stock pot on a 1 inch tall wire
grid trivet in the laundry tub, then fill the tub up with cold water to
about the level of liquid inside the stock pot. This time I got out my
digital thermometer and measured the temperatures a few times. I was
surprised at how fast the stock cooled... even faster than I had thought.

Here are the temperatures (in degrees F) of the stock and the cooling water
initially, after 15 minutes, and after 45 minutes:

Initial 15
Minutes 45 Minutes
Stock 160 85
75
Cooling Water 64 71
72

So most of the cooling took place within the first 15 minutes. At 45
minutes, it was essentially as cool as it was going to get (without changing
the cooling water). 75 degrees is pretty much room temperature. The rate of
cooling is going to change depending on the time of year and the temperature
of the incoming tap water. The greater the initial temperature difference
between the stock and the cooling water, the faster it will go. In mid
winter, my tap water was at 43 degrees, but I didn't measure stock cooling
at that time. In summer, my tap water will be even higher than it is now.

Some other parameters... the stock pot is a tall copper one, 8 inches in
diameter and 10 inches tall. There was between 3-1/2 and 4 quarts of stock
in the pot.

I suspect the results wouldn't have been quite so good with a low wide stock
pot, or one made of another material. With a low wide pot, I think there is
less surface area exposed to the cooling water, and there will be less total
cooling water in the tub. You can only fill the tub up to about the same
level as in the pot, or the pot will "float away". Using a trivet under the
pot is even more important on a low wide pot, as a greater percentage of the
available cooling surface area is on the bottom compared to a tall narrow
one.

I always strain the stock, then cool it. That is the method recommended in
all the cook books I have, and they also say not to cool totally covered or
the stock can turn sour. Regarding the initial stock temperature of 160
above, that is after straining, which cooled it off a bit. The temperature
coming off the stove was more like 170 (or even up to 180... I don't
remember what I saw).

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