Barbara Kafka's "Roasting" - Thermometer Calibration Question

[GB]

My brother in law got me this book for my birthday. I am very excited to be reading it and trying her techniques. I have only had a few minutes today to flip through so far, but she wrote something that I am wondering if it was a typo or not.

She was talking about instant read thermometers and how you should check their accuracy every once in a while. To do this she said to stick the tip into boiling water. It should read 210 F. Is this a typo do you think or is there a reason it would not be 212?

 

[jennyema]

Great book, isn't it? Make sure you do a chicken right away. But put some really thinly sliced potatoes under it or the smoke alrms will go off.

About the thermometer.....

Water boils at 212 at sea level. The boiling point decreases 1 degree for every 500 feet above sea level the water is boiling at.

You are no doubt somewhat above sea level. Find out how much and adjust accordingly. 210 would be for 1000 feet above.

An alternative is calibrating it in a glass filled with crushed ice and topped off with water so it is still mostly ice. Stir the slush mixture well. The thermometer should read 32.

 

[GB]

Yes I am loving this book so far!!!

I knew that about sea level and temps, but I find it odd that she would say the temp should read 210 without making any mention of seal level or anything else. Most people know that water boils at 212 so while I knew what she was getting , I just found the way she said it a little misleading.

This book is making me very hungry.

 

[jennyema]

It is weird, as she lives in NYC, I think ....

 

[Michael in FtW]

Well, unless she's discussing how the boiling point of water changes with the weather or altitude (barometric pressure) - I would stick with 212ºF. That's what the thermometer makers suggest for calibrating them.

For example, at standard 1-Atmosphere sea-level barometric pressure (29.92 inches Hg) - water boils at 212ºF. But, you have a high-pressure system sitting over you and the barometric pressure is 30.5 in/Hg - the boiling point of water is 213.07ºF. If you've got a low-pressure system sitting over you and the pressure falls to 29 in/Hg - the boiling point falls to 210.3ºF.

If you can find out your barometric pressure - you can use this Pressure Corrected Boiling Temperature of Water Calculator

If you have an old-fashioned wet-blub analog candy/fry thermometer (the kind with a liquid that rises in a glass tube) you can use that to determine the boiling point of water - and adjust your instant-read accordingly.

RE: Calibrating Instant Read Thermometers

There are two types - analogs that use springs and have a pointer dial, and digital. For the analog type - they should be calibrated on the high end of the scale - since that is where you are going to be using them. For digital types - they usually have two calibration settings - the Zero and the Span ... you calibrate the Zero setting for ice-water (32ºF) and the Span for boiling water (212ºF).

 

[jennyema]

That is exactly why I calibrate my thermometers in ice water!!

 

[Andy M.]

GB:

I assume you're referring to her book, ROASTING. I have that as well and really like it.

I use both boiling and ice water to check accuracy at both ends of the scale. You should never have an issue with a digital thermometer but it never hurts to be sure. Analog therms can go wrong and should be checked more frequently.

 

[GB]

Yep Andy I was talking about ROASTING (did I forget to mention that )

Yeah I know all about calibrating and how to do it. It just struck me as really odd that a woman who obviously knows her stuff would say to calibrate to 210 with no other explanation.

 

[Michael in FtW]

GB - if she didn't give a reason for calibrating at 210ºF - I would assume it was a typo. Writing a cookbook is a big task - editors are involved who don't know what they are doing (they edit text but don't necessarily know anything about the topic) ... things get overlooked from one revision to another ... and after you've read the same book over several times you just overlook mistakes like this.

 

[GB]

Yeah that seems to make the most sense Michael.

Toots, at least pull it out and give it another read before you decide. From what I am seeing, this is going to be a keeper for me for a long long time.