Accurate Temperature Control

[Zedition]

I'm trying to find an easy path to accurate temperature control while heating and maintaining the temperature of liquids. Currently I use the traditional method of a hot-water bath and thermometer. But I'm commonly getting temperature variances of 3C each way, which is more than I want to see. Volume of liquid I work with runs from a 1000ml flask to a 7 gallon pot, temp ranges run from 15C to 105C. I'm working with cheese-making, mushroom culturing and lautering, a few of my collection of back to the Earth hobbies. So while these are biological processes, this question is about equipment more commonly used by chemists.

 

I'd like to find a technique or affordable home-lab equipment that I can use to heat, maintain temperature in a narrow range and preferably manage the rate of heating as well – this is key for getting the right flavor in many kinds of cheese. Is there affordable and quality off the shelf equipment for managing a consistent liquid heating process, or some method using hot water baths that I've never been taught? By affordable, I mean under a couple hundred dollars.

[CaptainPanic]

You need a more precise thermostat, I think.

 

Also, make sure to mix the water bath, and also mix the flask or pot. The water temperature can change locally if you don't.

 

Finally, if you slow down the heating rate (the speed with which you heat up or cool down) you will have more control. If you have your water bath on a heating plate, the moment you reach your temperature, the heating plate is still extremely hot. Although the power will shut down at that moment, the heating plate will still transfer heat into your system. If you have it on a lower power setting, it will transfer less heat into your system once it shuts down.

[John Cuthber]

A quick look on eBay found this.

http://www.ebay.co.uk/itm/GRANT-FH15-10-80C-heater-water-circulator-pump-/180698328559?pt=UK_BOI_Medical_Lab_Equipment_Lab_Equipment_ET&hash=item2a1275adef#ht_500wt_1156

which is the sort of thing they use in labs. The temperature control is typically good to 0.1C if it's set up correctly.

(other bands etc. are available.)

[doG]

Sous Vide equipment is probably an affordable path....

[Zedition]

Excellent ideas and thank you!

 

I'll try slower heating first and see how that works for me. Part of the problem I think I'm having is that my water reservoir is small compared to the volume of fluid I'm heating. I'll typically use a 12 quart pot suspended inside of another shorter and wider 12 quart pot. It leaves about 3 quarts in the bath vs. 8 liter I'll measure out for heating. When lautering, it's a 32 quart pot inside of a 108 quart tub and you are right - much easier to control. So using a longer heat time definitely gives me a chance to catch over heating and adjust.

 

I'll also look at the other two pieces of equipment particularly for brewing. Cheese making is sensitive to disturbing the fluid, after you've congealed the proteins you need to keep large curds for good hard cheeses. But I've been wanting to scale up to doing 15 gallons at a spot instead of 5 at least with my 'house beer'. I'll need to figure out how equipment like this handles saturated fluids, beer wort can be up to 10% sugar and I intentionally use the hard spring water from my well when brewing. The complex salts of the artesian water add a unique flavor to even simple beers like a nut ale. But that same well water left some of the thickest sediment inside of pipes I've ever seen when I replaced the plumbing. So I'd hate to cake the heating elements with burnt sugar or calcium deposits, which is why I crossed off my idea of using an on-demand water heater (besides these heat too fast which would scald sugars).