Improving Vat/Griddle Heating

[Kern]

Here is the text of an e-mail I sent to John at Perfect Cheese yesterday.  I've got the Perfect Cheese controllers, griddle plus the 2 and 4 gallon vats.  I had purchased a 8" deep vat with a capacity of six gallons and was concerned about heating efficiency and had been working on this issue with John.  I pass it on to benefit all of you who are heating vats with griddles.


A big breakthrough!  My aluminum plate arrived yesterday so I thought I'd do some heating experiments with it using my 8-inch SS vat.  My first test was to heat things with the griddle setting at 400F both to calculate the heating rate and see if I had any hot spots that might scorch the milk.  With six gallons of water added the heating rate with constant stirring was 0.61 degrees per minute measured after the griddle had come to temperature.  I'd say the griddle light was off about 60% of the time.  After the rate test I let it sit for about 5 minutes with no stirring and then checked for hot spots with my fingers.  While I could feel some difference in temperature between various parts there were no spots where I could not maintain finger contact with:  The 1/4-inch aluminum plate was doing what I hoped it would do.  Still, I was disappointed with the rate.  Then I noticed that there was a gap between the plate and griddle.

I took some aluminum foil and doubled it 5 times to make it 32 layers thick and found that the gaps were smaller than this.  At this point I drained the pan, removed the aluminum plate and cooled the griddle.  I decided to fold up some foil sixteen layers thick and lay it on the griddle right above where the heating elements lay.  You can see this in the attached photo.  I refilled the vat with six gallons of water and ran the test again at a griddle setting of 400F.  I hoped that the foil laid on the griddle over the heating elements would result in a higher heating rate.  I got a heating rate of 0.85 degrees per minute and still no hot spots!

I surmise that the griddle is not flat and is cast aluminum designed so that grease drains toward the little hole on the long edge of the griddle.  The effect of this is that the aluminum plate only contacts the griddle only in the four corners where conduction occurs.  Elsewhere the griddle is heating the air in the gap between the griddle surface and flat aluminum plate.  By using the foil as in the picture I am heating more efficiently as the griddle is in contact with the aluminum plate via the folded aluminum foil.

I don't know that 16 layers is the right amount of foil to fully bridge the gap.  I am making a six gallon Caerphilly on Saturday and may try a few more layers in the central part of the griddle to see if it makes a difference.  During my test with the foil the light on the griddle was on about 60% of the time indicating that I was pulling heat away from the griddle faster than without the foil.

[BobbieGee]

Where do you get your vats? And could you post some photos?

Also, when you are making cheese with 6 gallons, how do you drain it? ....as when the recipe says to "drain the whey to level of the curds." I couldn't lift something that heavy.

Thanks for whatever help/info you can share with me...beginning cheese maker still trying to get the "right" equipment for my needs.
Bobbie Greiner
Bemidji, MN

[qdog1955]

Kern---I have been thinking of making a rectangular vat out of copper and using the griddle heating source. Any thoughts on that would be helpful.
Qdog

[Kern]

Qdog:  Copper is a great conductor of heat so I see nothing wrong with using it for a vat from that standpoint.  It is also used for vats for Alpine cheese but I've seen some citations saying it should not be used for cheese.