Adhesive Carboy Thermometer

I have an adhesive thermometer stuck on the outside of my glass 6.5 gallon carboy. It is positioned so that its top edge is 4 inches below the 5 gallon mark. Is it telling me the temp of the wort inside the carboy or the air temp of the room it is sitting in?

It's called a Fermometer. It tells you the temp of the contents.

contents... advertised accuracy is +- 1 degree F

Thanks! My LHBS told me the same but I wanted to verify. I've read that the contents will be a few degrees higher than the ambient surroundings. Cheers!

NWEagle said:

Thanks! My LHBS told me the same but I wanted to verify. I've read that the contents will be a few degrees higher than the ambient surroundings. Cheers!

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Yes, especially during the first few days of fermentation so you will want to keep a close eye on it to make sure it's not getting too hot. If you are doing an ale it could get close to 10 degrees higher than ambient if it's really going.

BryceL said:

Yes, especially during the first few days of fermentation so you will want to keep a close eye on it to make sure it's not getting too hot. If you are doing an ale it could get close to 10 degrees higher than ambient if it's really going.

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That's interesting, I'll definitely do that. I'm going to search for threads on the bad effects of fermenting at too high of a temperature, but if you know of any please post them. Thanks!

In the early stages of fermentation your beer is going to be susceptible to off flavors such as esters, which can be caused by high fermentation temps early on. I like to pitch my ales around 64 and then slowly raise the temp to about 68 over a couple days where I hold it for 3 weeks or so. This has always worked for me in avoiding off flavors.

A quick google shows lots of ideas and plans for fermentation chillers. Most are completely enclosed. If I plan to mainly produce ales and not lagers (at least not yet) I would think that a lid might be unnecessary. Would immersing in a water bath where I maintain temp at 60-63 degrees be sufficient? I'm thinking an inverted cardboard box over the top might create sufficient dead air space for a somewhat stable temperature.

I've never done the water/ice bath, but I know a lot of people on here do. It sound like a bit of work (changing out water bottles constantly)...maybe some others can chime in on that. I built myself the "son of a fermentation chiller" for around $75 and it works good for me. You can do a search on here for the plans. Some would suggest trying to get a fridge, but with my budget and space, the chiller works for me.

I pitched my first SIX brews at 75*f and they are all horrible, undrinkable, poisonous garbage. The next brew I used a styrofoam cooler with 2 20oz frozen water bottles to keep it at 66*f and I pitched it at 55*f. It is delicious after just 1 week in the bottle! And a stout no less.

2 weeks ago I got a 9cu ft chest freezer for $70 on craigslist. Then I got an unwired Ranco digital temp controller on eBay for $56 and wired it for another $8. So for $132 I now have set it and forget it temp control! I currently have a pale ale fermenting at a perfect 62*f. I highly recommend it. With the swamp coolers I had to constantly swap them 4 times a day and keep my freezer full of water bottles.

I have been submerging my fermentor in water during fermentation and it has done a great job of keeping the temp stable. Mind you my apt stays between 65 and 75 most of the time.

I was wondering if the fermometer would give me an accurate reading of the beer temp if it was submerged with the fermentor. Anyone tried this?

i have a thermowell with a probe in an actively fermenting IPA right now.

probe says 65. stick on thermometer reads 66.

^^^yup. I just have the probe from the temp controller suspended in the freezer, and it reads 1 to 2 degrees lower than the actual temp. I'm gonna pass on a thermowell since its so close.

This is great - less than a day after I inquired about my "fermometer," I'm planning to purchase and modify a used freezer! Currently there are 6 within 20 miles for under $100. Man, this is too much fun; this forum is awesome. Becoming a homebrewer was my wife's idea and I'm sure she'll back me when I show her all the evidence on this forum that temp control is vital for creating the best beer I can. Thanks all!

There's a TON of folks that make "swamp coolers". Use the search function and you'll see. Others just use a bathtub if available. Others build fermentation chambers (search for "Son of Fermentation Chiller" on here or using Google). I've converted an upright freezer by using a Love TSS2 controller.

Fermentation temperatures (and process) play a HUGE (some would say the most significant) role in the overall taste and quality of the beer you produce. A good fermentation can 'fix' production problems. I try to learn about the yeast I'm using and the style beer I'm making before I jump into it. I want to know what the intended beer taste is and what the yeast will do to influence those flavors. Knowing how the yeast behaves at different temperatures will help you target the temperature you want to ferment at.

NWEagle said:

This is great - less than a day after I inquired about my "fermometer," I'm planning to purchase and modify a used freezer! Currently there are 6 within 20 miles for under $100. Man, this is too much fun; this forum is awesome. Becoming a homebrewer was my wife's idea and I'm sure she'll back me when I show her all the evidence on this forum that temp control is vital for creating the best beer I can. Thanks all!

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Here's something you might want if you go with a LOVE controller...

https://www.homebrewtalk.com/f51/help-wiring-love-controller-154450/

https://www.homebrewtalk.com/f51/love-controller-freezer-its-alive-error-erp-alarm-237646/

The first link has a decent wiring diagram. The second has some troubleshooting stuff on it.

JonBoy47 said:

I was wondering if the fermometer would give me an accurate reading of the beer temp if it was submerged with the fermentor. Anyone tried this?

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NO! Don't do that, I learned this mistake the hard way. Fermometer submerged in water will become unoperable while its soaked in water for a week or so during fermentation. I lost one that way, RIP
Now I keep 2 carboys without fermometers so I can use them with swamp coolers

paraordnance said:

NO! Don't do that, I learned this mistake the hard way. Fermometer submerged in water will become unoperable while its soaked in water for a week or so during fermentation. I lost one that way, RIP
No I keep 1-2 carboys without fermometers so I can use them with swamp coolers

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+1. Ruined mine that way.

Same happened to me, what do y'all do to monitor temps while using a swamp cooler?

I use a pool thermometer, I just tie it around the neck of my carboy and it rests against the glass about 3/4 of the way into the cooler.

I guess any waterproof thermometer in the water close to the fermented should work, just wasn't sure how accurate it would be compared to a stick on.

I know actual ferm temps are higher

I used to just use the peel-and-stick temp and adjust my water to get the internal temp the what it needed to be. I'd just drop my brewing thermometer in the bucket while I went to get the ice and remove/read it upon my return. I'd dump in some ice and mix, leave it and come back an hour later to see the results.

Adamb258 said:

I guess any waterproof thermometer in the water close to the fermented should work, just wasn't sure how accurate it would be compared to a stick on.

I know actual ferm temps are higher

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When I was using glass carboys in a water bath, I tested the temp inside the fermenter and compared it to the water temp. It was only as little as 0.2* higher during high Krausen. I always kept the water level at the same level as the brew. Glass transfers heat and cold really well.

Also the water will move around (rise at the edge of the slightly warmer ferment vessel) and mix real well. So the water temp even on the extreme edge will be within 0.1* of that close to the vessel.

I just use instant read digital thermometer when I ferment in swamp cooler. Dip it for minute, then read Before that I had glass one, but its broke

Anyone know why my thermometer (that I just bought) has 3 different colors for 3 different temps (62, 64, and 66)??? One color is blue, the other is green, and the other is tan...Which one is the accurate one?

JeffoC6 said:

Anyone know why my thermometer (that I just bought) has 3 different colors for 3 different temps (62, 64, and 66)??? One color is blue, the other is green, and the other is tan...Which one is the accurate one?

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Green is the "actual" temp.

pabloj13 said:

Green is the "actual" temp.

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Thank you!