Always calibrate your thermometer!

[nmarolf]

Just a reminder to everyone to make sure you calibrate your thermometer. I bought a new one after my old one broke. I never calibrated it and after having 3-4 beers come out way to thin, I started thinking about things I had done differently in those beers, and then I realized I had bought a new thermometer.

To make a long story short, my brand new thermometer was reading about 3-4 degrees F below the real temperature. That means I was mashing between 147-150. The worst part was my first home-grown hop pale ale (used all the hops I got from my first year crop) that i'm now drinking tastes too much like water. It is drinkable, but not all that fun to drink.

Anyway, check your thermometers everyone, even if you aren't having problems.

 

[KayaBrew]

I calibrate BOTH my thermometers every brew day. Good advice!

 

[passedpawn]

Just a reminder to everyone to make sure you calibrate your thermometer. I bought a new one after my old one broke. I never calibrated it and after having 3-4 beers come out way to thin, I started thinking about things I had done differently in those beers, and then I realized I had bought a new thermometer.

To make a long story short, my brand new thermometer was reading about 3-4 degrees F below the real temperature. That means I was mashing between 147-150. The worst part was my first home-grown hop pale ale (used all the hops I got from my first year crop) that i'm now drinking tastes too much like water. It is drinkable, but not all that fun to drink.

Anyway, check your thermometers everyone, even if you aren't having problems.

If it was reading low, then your actual mash temp would have been higher. I'm guessing the problem lies elsewhere. Your advice, though, is still great advice.

 

[nmarolf]

If it was reading low, then your actual mash temp would have been higher. I'm guessing the problem lies elsewhere. Your advice, though, is still great advice.

Yikes. You are right. And I thought I had it figured out. Maybe it was reading higher on those brew days.

Still, my sage advice stands.

 

[TipsyDragon]

ok... how do you calibrate a thermometer?

i believe you when you say the reading can be off. but how can you really check.

 

[Rushis]

Water/ice slurry will always be 32F. Boiling distilled water adjusted for elevation will always be 212.

 

[TipsyDragon]

ah thank you. that makes sense.

lol i was thinking of comparing the reading on one to the reading of another. there would be no way of knowing which one was off and by how much.

 

[nmarolf]

Ok, so after a week or so of carbonating and maturing, both beers are fantastic.

 

[AirRageous]

I live and brew at 5000 feet above sea level and my boil temp is only 203F. If you are above sea level, make sure you take that into account when you calibrate. Freezing temperature is NOT effected by altitude so go with 32F or 0C for that. The rule-of-thumb is approximately 1 degree F for every 500' in altitude. Here is a boil temp / altitude chart for quick reference.


Altitude/Boiling Temperature

Sea Level=212 degrees F

984 ft.=210 degrees F

2,000 ft.=208 degrees F

3,000 ft.=206 degrees F

5,000 ft.=203 degrees F

7,500 ft.=198 degrees F

10,000 ft.=194 degrees F

20,000 ft.=178 degrees F

26,000 ft.=168 degrees F (If you are brewing on top of Everest)

 

[jasonsbeer]

I came across a web site that lets you adjust boiling temp for altitude and barometric pressure. It appears that a swing in the pressure can move boiling temps 1 or 2 degrees.

http://www.csgnetwork.com/h2oboilcalc.html

 

[azscoob]

I have two dial thermometers, one has blue lettering, one has red lettering, both are frome the LHBS, I calibrate the red one in boiling distilled water and use that one for mash temps and strike water temps, the blue one I calibrate in icewater and use it for my wort chilling and starter temps, I calibrate every brewday, the cross check usually gets me a boil temp on the blue one of 199° and a freeze temp of 40° on the red one. those cheapy thermos work well in a limited range but not the full sweep needed. I have a good k-type that I never use oddly enough!

 

[artguy]

Water/ice slurry will always be 32F. Boiling distilled water adjusted for elevation will always be 212.

I do have a question about how exactly to use this info, though, because thermometers can be off by different amounts at different temps. I have three thermometers that are all within one degree at 32F, but around typical mash temps of 150F they vary by as much as 7 degrees. As far as I can tell, they don't follow a definite pattern either, because the one with the lowest reading at 150F had the second lowest at boiling.

 

[humann_brewing]

I forgot where I read this but maybe someone can help. There was some sort of liquid that would boil at 170 and thus a lot closer to mash temps for accuracy.

Anyone know what I am talking about?

 

[jasonsbeer]

I forgot where I read this but maybe someone can help. There was some sort of liquid that would boil at 170 and thus a lot closer to mash temps for accuracy.

Anyone know what I am talking about?

Ethanol, I think.

EDIT FROM WIKIPEDIA: Boiling point of ethanol: 78.4 °C, 352 K, 173 °F

 

[azscoob]

most alcohols boil at 170-172, at least thats what I hear on discovery channel about 'shine makin. use an electric element for this, boiling alky and fire is bad juju

 

[Rushis]

boiling alcohol + ignition source = yeah kitchen fire :rockin:

The water/ethanol azetrope (95.5% Ethanol and 4.5% water) boils at 78C. In theory, 190+ proof ethanol boiled until a constant temperature is reached could work. But, it doesn't seem like a very safe idea.

If your thermometers are that poorly graduated, it's probably best just to buy a better thermometer. A good lab grade thermometer only costs around $20 and comes with ANSI certification. Use that as primary standard to calibrate the "lesser" temperature measuring devices.