Tony1951
Bungling Amateur
Some of you may be more used to using a thermometer to measure the temperature of a liquid than I am. I never worked in a lab, or a factory where I needed to take temperatures to an accurate degree - not until I was trying to mash my malt at 68C did I need to bother about stuff like this. But it's dead simple isn't it? Just stick it in and then read the scale?
No it isn't. You can easily get it wrong like I did.
For a few weeks I've been puzzled by my readings at boiling point. My thermometer read 105C when the wort was boiling. I alternatively convinced myself that this was because the Young's Brewing Thermometer (about ã3.50) was rubbish, and I said so on here. Then I thought it was all about the wort being sugary and therefore boiling at a higher temperature.....
It does, but not as high as 105C with a wort of about 1060 specific gravity.
Then I noticed that when placed well into the boiler, but with the bulb nowhere near the hot element, it was still reading about 104C, IN PURE WATER. Something is wrong here I thought, so I ordered a neat little digital thermometer from ebay and tested that. It worked perfectly, but when I put the Youngs thermometer in the same shallow pan, that was also reading almost dead on 100C.....
What the hell is going on here? So, I started fiddling about with the thermometer at different depths and the thing changes when you do that.
After finding this queer behaviour, it started to dawn on me that I shouldn't be that surprised. If only the bulb is in the hot water, you will get a certain amount of expansion on the fluid inside the glass. If I also submerge another nine or ten inches of the capillary tube in the boiling water, in a boiler say, that too will be expanded and the indicated temperature will rise, even though the real temperature doesn't.
So I began Googling on the subject and discovered that there are different types of glass tube thermometers which are calibrated to be either partially submerged or fully submerged, and that it usually says how far to submerge your thermometer on the side.
I put on my specs and took a look at my Young's thermometer and it says on the side near the top "76 millimetre Immersion".
Did I feel a bit stupid? Yes.
I repeated the boiling test submerging 76 mm of the thermometer in the boiling water and what do you think the read out was? It was 100C.
I've marked the distance 76mm from the lower end of the bulb and my mashing temperatures might be more accurate now so I might get the kind of beer I want. A difference of three or four degrees might make a big difference to the sweetness, or alcohol content of a brew so it is worth knowing this fact.
reference: http://www.amrl.net/amrlsitefinity/default/Resources/newsletter/Spring2011/8.aspx
No it isn't. You can easily get it wrong like I did.
For a few weeks I've been puzzled by my readings at boiling point. My thermometer read 105C when the wort was boiling. I alternatively convinced myself that this was because the Young's Brewing Thermometer (about ã3.50) was rubbish, and I said so on here. Then I thought it was all about the wort being sugary and therefore boiling at a higher temperature.....
It does, but not as high as 105C with a wort of about 1060 specific gravity.
Then I noticed that when placed well into the boiler, but with the bulb nowhere near the hot element, it was still reading about 104C, IN PURE WATER. Something is wrong here I thought, so I ordered a neat little digital thermometer from ebay and tested that. It worked perfectly, but when I put the Youngs thermometer in the same shallow pan, that was also reading almost dead on 100C.....
What the hell is going on here? So, I started fiddling about with the thermometer at different depths and the thing changes when you do that.
After finding this queer behaviour, it started to dawn on me that I shouldn't be that surprised. If only the bulb is in the hot water, you will get a certain amount of expansion on the fluid inside the glass. If I also submerge another nine or ten inches of the capillary tube in the boiling water, in a boiler say, that too will be expanded and the indicated temperature will rise, even though the real temperature doesn't.
So I began Googling on the subject and discovered that there are different types of glass tube thermometers which are calibrated to be either partially submerged or fully submerged, and that it usually says how far to submerge your thermometer on the side.
I put on my specs and took a look at my Young's thermometer and it says on the side near the top "76 millimetre Immersion".
Did I feel a bit stupid? Yes.
I repeated the boiling test submerging 76 mm of the thermometer in the boiling water and what do you think the read out was? It was 100C.
I've marked the distance 76mm from the lower end of the bulb and my mashing temperatures might be more accurate now so I might get the kind of beer I want. A difference of three or four degrees might make a big difference to the sweetness, or alcohol content of a brew so it is worth knowing this fact.
reference: http://www.amrl.net/amrlsitefinity/default/Resources/newsletter/Spring2011/8.aspx
