SS Mashtun temp drop

A few months back I purchased a stainless steel kettle with a thermometer, valve, and bazooka screen that I’ve been using as a mash tun (that was the intention when I bought it). I notice that I suffer a significant drop in temp over the course of an hour, about 4 degrees in the first 30 min and then another 4 degrees or so by the end of the hour…

This seems like it’s really taking a toll on the fermentability of the brew… The past few batches I did I landed at 151 after doughing in and then the temp dropped down to almost 140 at the end of the hour… I hit my OG just fine, but after weeks fermenting those batches only came down to FGs of the mid to high 1.020s… I’m attributing this to the drop below 149 degrees lending too many unfermentables? I’d never had a problem getting nice low 1.008 – 1.010 FGs when I was using an insulated cooler which kept my temp more stable…

I haven’t changed any other process – my yeast pitch rates are healthy, these brews were only 1.050-1.060 OG, and I’m leaving them for 3-4 weeks fermenting at around 70 degrees… but I’m still getting 1.026+ FGs, the sweetness is ruining what should otherwise be a good beer…

Any suggestions? I’ve read about wrapping it in something to help insulate it, I’m just not too sure how much that’s going to help (I do keep the lid on it too btw).. I don’t have a true false bottom so I can’t add direct flame, and I’m trying to avoid the additional work of adding hot water to bring the temp up…

sosloe said:

A few months back I purchased a stainless steel kettle with a thermometer, valve, and bazooka screen that I’ve been using as a mash tun (that was the intention when I bought it).

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Are you spot checking you mash temperature in different location in the mash with different thermometer or just depending on the installed one?

lower mash temperatures mean more fermentable content. Higher mash temp leads to more sugars that the yeast can't process.

I have a reflectix sleeve that I put around my keggle mash tun, and a plastic lid wrapped in the same stuff that I put on during the mash. it isn't perfect, but I only lose a degree or three when I mash for an hour without kicking on my HERMS system.

My guess is that you are in fact mashing too high but since your thermometer is closer to the outskirts of your pot the temp isn't being recorded properly.

get a cheap waterproof digital from amazon, then check different places of your grist during the mash.

I guess that might be the case then, I'm not spot checking anywhere else. Weird though because I'm using a mash temp calculator and stirring the mash around pretty well to get the temp evenly distributed. I guess I'll try to insulate it too to see if it helps at all.

Cheers!

Finally figured it out...

It wasn't actually a problem with fermentability at all... I also purchased a refractometer at the same time as my new kettle and I wasn't aware until some research about fuzzy readings over the past couple days led me to see that FG readings on refractometers need to be corrected... I had a 1.070 OG finish at 1.035 and I was freaking out... After running it through the correction formula it said the FG was about 1.016... I sampled the batch today and the hydro reading confirmed... Problem solved :cross:

If you're not direct firing your mashtun, then wrap that sucker in reflectix. I have about 3 layers or more on all surfaces of the keg MT. Works great and only lose about 1 degree..

I have a new experiment for you to try if you have iodine. Use the iodine to test a drop or 2 of wort at different times during your hour long mash to see just when the conversion is done. You may find that your conversion is done much sooner than you think and that your temperature loss is nothing to worry about.

I go one step better on the keggle I use a disc shape piece of reflectix that I place on top of the mash to reduce the headspace in the keggle holds temp even better since the headspace is what makes you lose the temp to begin with

I went for a slightly more ghetto version and just put an old winter coat around my pot while mashing. Easy enough to get on and off by zipping and unzipping. Less than 1 degree change now over the hour.

Dougie... I am going to give that a try... makes sense to me! (Why didn't I think of that!?!)