Mash Penetration is Important

[Common]

So after having some beers finish at a higher gravity than I planned on, some being sweeter than planned, and every single Extra Stout I brewed stop at 1.032, I now realize the ugly truth. I believe some of you on here suggested I was mashing too high and maybe my thermometer was off. My thermometer is accurate, and 156 isn't too high of a mash temp... however, you were still right in different ways.

I got to thinking maybe the top of the mash is cooler than the bottom, even though I stir up down and all around. So I got a lab type thermometer and tested it against my digital tonight. The lab type is quite a bit longer. I tested them both at room temp and heating my sparge water and they were exactly the same.

I then mashed in, stuck in my digital and stuck the lab type down as far as it would go and I could still read it. Here are the results...



That is pretty much a 10 degree difference! No wonder my FES was getting stuck - I was mashing at 166!

So, I wouldn't trust digital unless it's got a long probe. 3" just can't penetrate enough. You're going to need at least 8"

By the way, I have always used BeerSmith to calculate strike temps. My first 2 or 3 brews I used my friend's long dial thermometer then switched to that digital one.

[Big_John]

Good to hear you discovered what the problem was. FWIW, you can easily make a simple psuedo thermowell to use with almost any digitial thermometer probe. Just use a section of 1/2" copper pipe capped on one end. Shove the probe into the pipe all the way to the bottom. You now have a waterproof thermowell "wand" that you can place anywhere in the mash you like. The copper is an excellent heat conductor, so the response time will be very fast. I have been using one like this for a couple of months now with great results. It's simple, cheap and effective. So much so that I am amazed no one has thought of doing it this way sooner.

I use a section of 1/4" wood dowel rod to push the probe to the bottom of the copper tube. I leave the dowel in the tube to hold the probe in place securely and touching the bottom cap.

[Common]

Cool. I may do that. Thanks.

[Big_John]

I have mine mounted vertically on a cross bar above the MT. In this pic I used a fiberglass rod to push down the probe and hold it in place. It's fully adjustable vertically so I can place it where it will monitor the average mash temp well:





IMO, determining the actual average mash temperature is the key to successful mashing. It made a huge difference for me.

[Niedermier]

I have been having trouble with my mash temps on my last few brews. The biggest problem is that I have been getting different temp readings from my glass floating thermometer and my digital probe. For example, the porter I brewed last week could have been mashed anywhere between 147-155 depending on which thermometer I go by. I need to be more consistent with how I take temp readings and the copper tube thermowell sounds like a good start.

[Big_John]

IMO, nearly every problem I read about where the ferments don't finish out as desired it is mostly due to the mash temps being too high. I had the same problem and it took me awhile to find a solution. I first discovered that my expensive large dial thermometer was fucked up. When I checked it against a glass lab thermometer I found it to be off my more than 8 degrees! I tried calibrating it, but that did not solve the problem as it would not stay in calibration and it was not consistent over the entire range. It showed no visible sign of damage at all. I paid about $50 for that piece of junk. It is now a paperweight. I bought a digital thermocouple type traceable thermometer and built the psuedo thermowell to use with it. I position the thermowell half way between the center of the mash and the outer wall and half the depth of the mash. I figure this will give me the best indication of the average mash temperature. I do a continuous recirculation in order to maintain more or less uniform mash temperatures and it seems to work well. My beers are consitently finishing out just fine. This was not the case previously. You only need be off by as little as four or five degrees to the high side in order to have problems and this is particularly true if you are mashing on the high side to begin with. Again, IMO many people think they may know what their mash temps are, but the reality is sometimes quite different. I no longer trust any of the bi-metal dial type thermometers. I'm done with them. Glass lab type thermometers are very reliable and usually well calibrated. I have a high degree of confidence in my digital thermometer, but I do still check it now and then against the glass thermometer just to be sure. Try the copper tube thermowell thingy. It's very cheap to make one and they work like a champ.

[salad 419]

Big John, just a few quick questions:

Do you fill the copper tube with water? OR, the probe is actually touching the copper and reading that temp?

[Big_John]

Salad,

I don't fill the tube with anything at all. The probe is touching the bottom of the tube. Even if it were not touching the bottom, the temperature inside the tube would be very, very close to the mash temp as the tube itself is completely surrounded by the mash, so the air in the tube will also be very close to the mash temp. The response time will be best if the probe is actually touching the copper, but the difference would be rather insignificant IMO. Copper is a really good heat conductior. Really, really good!

[rdwj]

Very valuable info John! The homemade thermowell is a great solution to several problems I've been having.

Do you recirc through that cpvc contraption? I've never seen one like that.

[Big_John]

rdwj,

Yes, I use it as a return manifold during the recirculation and also as a manifold for the sparge water. Like the thermowell, it is fully adjustable vertically to accomodate varying batch sizes. The elbows on the end of the "H" are not glued on and can be rotated. I point them in opposing direction which creates a gentle swirl effect for even wort/water distribution. I used a couple of screw eyes through the side of the wood cross bar as set screws for both the thermowell and the manifold to hold them in position once adjusted to the desired depth. The hook on the end of the cross bar holds the feed hose in position and keeps it out of the way. The cross bar can easily be removed and set aside in a plastic bucket when I need to stir the mash. Nothing, including the digital thermometer needs to be removed when doing this.