Thermometer Woes, FG problem.

[archiefl98]

My first batch of All-Grain was a simplistic recipe, an American Pale Ale that was just about as close to a SMASH recipe as possible. I used my True Brew floating thermometer for the brew. The same thermometer I've had for 10 years of extract brewing and had used constantly for anything liquid. It reads dead on 32F at freezing and dead on 212F at boiling. The first batch came out great. OG 1.050, FG 1.015, Mashed at 154F for 60 minutes according to the True Brew floater.

I brew up my second batch -- same recipe, using a couple of new True Brew floaters and using an average measurement to avoid hot/cold pocket measuring. Mashed at 154F for 60 min. OG 1.052, FG 1.012. Not bad.

Then I started reading about thermometers here on HBT. I found out a lot of people found the True Brew to be unreliable and prone to breaking in their mash tun. So I pulled out my Taylor 808-4 digital remote probe thermometer that I've used for smoking meat with for the couple years. (Since I get my pulled pork to about 175F to know that it's safe to eat, I figure it's pretty close to the same range.)

After testing the Taylor at freezing and boiling, it appears to be dead on as well. Then the real test. I heat up strike water for my AHS Guinness clone and the True Brew reads 10F higher than the Taylor in my strike range. (Taylor reads 167F, True Brew reads 177F!)

I chalk it up to the True Brew thermometers being crap, and go with the Taylor for measuring everything. Mash stays at 149F for 75 min. (Want to make it dry.) Sparge with 170F water. OG 1.044.

A few days later I use the Taylor to make the AHS Scottish Heavy 70 /- kit. Mash at 154F for for 75 min. OG: 1.058. Efficiency appears to be great! Iodine test on both batches reads full starch conversion (no black)

A couple weeks go by and I go to read my FG of the Guinness clone -- 1.018. I pitch some rehydrated dry yeast onto it (Muntons). Then I read the Heavy 70 /- and the FG is 1.022! I give them another week in the fermenter after a swirl and a warm up to 75F. The Guinness is still at 1.018. So I knock the Guinness out onto a Notty cake I just took another pale ale off from hoping that it was just a bad round of yeast or something. A week later -- 1.018. Grrr. I keg a sweet stout. The heavy's still sitting at 1.022. I keg that too. Mad as !@#$.

Both had healthy yeast. Guinness went onto a yeast cake from an Irish Red that fermented fully. (FG 1.012) The Heavy had a 2L starter. Both fermented at about 69-70F. Guinness used Wyeast 1084, Scottish used White Labs WLP028. No infections or anything like that -- in fact they taste quite good, just not as dry as either should be.

So I go back to the Taylor thermometer. If it's reading low, then I'm mashing high, which means I'm getting more unfermentables, right? Well I compare the Taylor to my NSF certified roaster thermometer -- dead on. I compare it to my NSF certified quick-read thermometer -- dead on. I compare it to SWMBO's 30 year-old candy thermometer -- dead on. The True Brew, 10F off from 140-180F.

So here's my question: Do I go back to using the True Brew thermometers and see if I can make consistently mashed wort that ferments out where it should, or do I drop $100 on a Thermapen, since I've read rave reviews about them here on HBT?

Thanks for reading. I know it's long. I know it's boring. And yes, I know I'm b!@#%ing. If anyone else has any insight as to what could be the problem, let me know.

 

[scinerd3000]

do whatever you were doing to get beer the way you want it. I use a digital thermometer and i love it but if a floater is more your style and you were able to turn out good beer with it-why not use it. The down side is that if it is actually off, you will have a hard time regulating your recipes on someone elses system per-se since they will have different thermometers. I'm a scientist so i care about such things but if your just doing this to make good drinkable beer and not for the science and repetition of it then i doubt its going to matter.

 

[archiefl98]

I really do want to have consistency/repeatability between brews. Obviously I'm just moving into AG brewing. I just did another test today. I measured with both the digital (along with the nsf certified dial therms) and the true brew. I went by the true brew readings. According to true brew I mashed Edwort's Bavarian Hefe @ 154F for 90 min. According to the digital and the nsf's I was at 146. I guess if it ferments out to 1.009 I'll know I was low. If it ends up within range (hoping for 1.015 or so) then I'll figure that the true brew was closer to actuality.

There was actually a lesson in one of my high school science classes regarding Accuracy vs. Precision. I guess I'm actually starting to understand that concept.

 

[archiefl98]

Here's my update to the issue.

So I ordered a Thermapen and decided to do a few tests. Not sure how scientific I am with them, but to me it explains my issues.

Test 1: Freezing

Used a 4-quart pan with snow and tap water. Let it sit for about 15 min and stirred it up pretty well.

• Thermapen: 32.2F
• Taylor 808-4: 32F-33F
• True Brew Floater: 32F

Test 2: Boiling

Brought the same pan of water up to a nice rapid boil on the stovetop.

• Thermapen: 211.9-212.1F
• Taylor: 212F
• True Brew: 212F

Test 3: Mash temp 150F

This is where it gets interesting.
Test 3A is to use the Thermapen as the reference of being correct

• Thermapen: 149.9-150.1F
• Taylor: 144F-146F
• True Brew: 152F

Test 3B is to use the Taylor as the reference of being correct:

• Thermapen: 161F
• Taylor: 150F-152F
• True Brew: 165F

To me, that would mean that I've found the reason that my Guinness clone didn't ferment down past 1.018. While I may have thought I was at 150, I was actually closer to 160F, thus making a highly-unfermentable wort. This also explains that when I use my True Brew to hit 154, I'm really hitting around 152, thus fermenting out to 1.012-1.016 for some of my first brews. I'm definitely going to use the Thermapen going forward and hope my beers keep getting better.

Thermapen FTW!