11 replies to this topic

[CarlosM]

alright so I mentioned a while back I found the culprit of my under attenuating beers. A bad thermometer so a few weeks ago I bought anew thermometer (bettar than the dial one I got for 10 bucks) So just now I calibrated both of them to ice water because thats the standard. To make sure of proper calibration I started boiling some water. The water is clearly boiling with huge bubbles and steam yet both of them say 180. Any one care to explain whats going on?To be honest all I really care about is the thermometer being able to read temps right so I can mash properly. Boiling is clearly a sign of 212 but what am I doing wrong?ETA:Just submerged the new thermometer more into the boiling pot and it reached 200 some odd degrees alot better than the old one.

Edited by CMS, 10 November 2009 - 03:39 PM.

[Humperdink]

How high are you?

[shmgeggie]

link

The simplest and cheapest way to calibrate a thermometer is through either the use of ice water or boiling water. Distilled water should always be used as dissolved solutes in tap water can significantly affect both freezing and melting points. Another important consideration is the altitude (Table 1) at which calibration is being performed. At sea level, pure water boils at 212° F but at 10,000 feet above sea level it boils at only 194° F. Barometric pressure also has an effect on boiling point but the effect is much less than that of altitude.

[shmgeggie]

How high are you?

His profile says Chicago - about 600'. When I went through this, I was surprised that in Spokane, at only 2000', water boils at 208F.

[CarlosM]

link

yea Im using tap water, distilled water is so expensive though so it kinda discourages me get it to calibrate it with.

[DaBearSox]

yea Im using tap water, distilled water is so expensive though so it kinda discourages me get it to calibrate it with.

a gallon of distilled water at Jewel is probably not more than 2 bucks.

[RommelMagic]

yea Im using tap water, distilled water is so expensive though so it kinda discourages me get it to calibrate it with.

I buy it all the time. Expensive? It's only about a buck here. Besides, don't you want better beer?

[jasonrobertcohen]

I buy it all the time. Expensive? It's only about a buck here. Besides, don't you want better beer?

Great point. Many people forget why we're doing this. If homebrew were actually about saving money, we'd all be better off spending the 3-6 hour brew session working a paying job and buying beer off the shelf. For us, it's all about a pursuit of knowledge and experience.Spend the buck. Measure the difference between distilled water and tap water. Experience it.

[Jimmy James]

If you correctly calibrated at 32 in ice water and you're getting 180 in a rolling boil then something is off with the scale on your thermometer. It is not uncommon for cheap thermometers to be accurate in a more narrow window than 32 - 212. I think you're best bet would be to find someone that has an ASTM thermometer (someone in your local brew club or who shops at your LBS might have one) and calibrate your thermometers you'll use for mashing at 150. Then they should be accurate across the range of useful brewing temps where accuracy is required. You can buy ASTM thermometers from lab supply companies for something like $35 that are accurate to +/- 1 degree across a range much larger than you're brewing needs.

[Fatman]

Great point. Many people forget why we're doing this. If homebrew were actually about saving money, we'd all be better off spending the 3-6 hour brew session working a paying job and buying beer off the shelf. For us, it's all about a pursuit of knowledge and experience.Spend the buck. Measure the difference between distilled water and tap water. Experience it.

Or build a setup to distill the water yourself.

[pete maz]

If you correctly calibrated at 32 in ice water and you're getting 180 in a rolling boil then something is off with the scale on your thermometer. It is not uncommon for cheap thermometers to be accurate in a more narrow window than 32 - 212. I think you're best bet would be to find someone that has an ASTM thermometer (someone in your local brew club or who shops at your LBS might have one) and calibrate your thermometers you'll use for mashing at 150. Then they should be accurate across the range of useful brewing temps where accuracy is required. You can buy ASTM thermometers from lab supply companies for something like $35 that are accurate to +/- 1 degree across a range much larger than you're brewing needs.

Exactly. I see all the time where people "calibrate" their thermos in ice or boiling water, but this really means very little at 150F. You always want to verify/calibrate at the temp it will be used. As Jimmy says, you're much better off getting a calibrated reference thermometer that you can use to verify/calibrate the other thermos in your brewery. The glass bulb type is pretty cheap and generally don't go out of calibration. Here's a link to some that are really cheap. They offer a calibration certificate for something like $35, but you really don't need to bother with that.

[Stout_fan]

About 30 years ago I bought this one for color film work. It was $35 back then.WOW have they gone up. Guess I'll have to treat the reference with a bit more respect now!Break it and I'm out two bills.linkI have a metal case for it as well.