When to do diacetyl rest and how to warm up fermenter?

[njohnsoncs]

I'm currently fermenting my first lager (a Pilsner) and I have a couple questions.

1. When do I do the diacetyl rest (I've seen a lot of conflicting information from many different sources). Do I start warming up the fermenter when it is a couple gravity points away from expected FG or a while before that since it will take a few days (~4-5 days) for the fermenter to get to 65 F?

2. I currently have it fermenting at 52 F in my chest freezer. How should I warm it up for the diacetyl rest? I don't have any heat source. The ambient temperature in the room can be set as high as I need. Is it OK to set it to 65 F, pull the fermenter bucket out of the freezer, and let it warm up to room temperature? Will it warm too fast or too slow?

Thanks!

 

[Home_alone1]

I do my rest as the krausen starts to drop , you want to do it while there is still some sugar for the yeast to chew on. I don’t use a hydrometer for this so someone else can post what a good gravity reading is to do it at.


Don’t pull it , go to a gun store , cabellas , or amazon and order a golden rod , it’s used to keep guns from rusting in a safe but I use the large one as a chest freezer heater . I mounted it to the lid of the chest freezer using those eyelet screws from Home Depot and then used copper wire to attach the rod to the eyelets . Works great and it’s cheap. I also put a small desk fan inside to keep the heat evenly distributed. Mine is plugged into my inkbird controller and I can control temps temps with just a push of a button.


In the mean time just turn off the freezer and open the lid , if the ambient temp is 65 it will warm up In not to long .

 

[Home_alone1]

 

[mongoose33]

I raise the temp when the krausen falls. If you're looking for a heat source, IMO you should warm the fermenter, not the ambient. You can do this with a reptile mat like this one:

https://www.amazon.com/dp/B00P7U259C/?tag=skimlinks_replacement-20

Just wrap it around the fermenter, connect to a control whose temp probe is reading the temp of the wort, and you're good to go.

I use a piece of closed-cell foam like this:



I press the temp probe against the fermenter and keep it there with a bungee cord. I wrap the reptile mat around the fermenter too, using string or bungee cords. Plug into an Inkbird controller and you have full temperature control.

 

[Bamos6928]

I use a fermwrap, an old fridge and an Inkbird dual stage temperature controller and they work awesome!!! Gives you complete control over fermentation temps.

 

[Bamos6928]

As far as when, I start ramping up my temperature as soon as my krausen starts to go down or the bubbling in my airlock slows.

 

[cactusgarrett]

If you want numbers, I typically ramp my lagers once they get within 25% of the expected FG. I often use fermenters that i can't see into so, gravity readings are my easy indicator. You want to raise the temp while the yeast are still working to encourage them to cross the finish line just fine. Some would argue that if you pitch enough, healthy yeast, you shouldn't need a d-rest. I, myself, like the extra insurance.

 

[Qhrumphf]

If you want numbers, I typically ramp my lagers once they get within 25% of the expected FG.

This. Start free-rising when you're 75% to your FG.

Pull it out and let it warm on its own. Don't artificially heat it.

Once you're at your FG, give it another 2-3 days and start checking it. Don't worry about the temp it actually reaches.

Better than simply sampling it, do forced diacetyl testing. https://spikebrewing.com/blogs/ask-a-pro/an-easy-diy-diacetyl-test

That test will not only highlight diacetyl but metabolize its precursors INTO diacetyl. If after doing that you don't perceive it, you're good to drop temp whenever you want.

And as long as you're not fairly diacetyl blind (which a significant number of people are, my personal sensitivity is on the low side and took a LOT of work to train it), it's as effective as actual lab testing for VDKs. If you're a super-taster for diacetyl, perhaps even more effective.

 

[Beer666]

This. Start free-rising when you're 75% to your FG.

Pull it out and let it warm on its own. Don't artificially heat it.

Once you're at your FG, give it another 2-3 days and start checking it. Don't worry about the temp it actually reaches.

Better than simply sampling it, do forced diacetyl testing. https://spikebrewing.com/blogs/ask-a-pro/an-easy-diy-diacetyl-test

That test will not only highlight diacetyl but metabolize its precursors INTO diacetyl. If after doing that you don't perceive it, you're good to drop temp whenever you want.

And as long as you're not fairly diacetyl blind (which a significant number of people are, my personal sensitivity is on the low side and took a LOT of work to train it), it's as effective as actual lab testing for VDKs. If you're a super-taster for diacetyl, perhaps even more effective.

I have always fermented around 10c for 2 weeks then raised it to 20c for a week before cold crashing. Would you consider this bad practice? I am fairly sure i cant taste diacetyl in my beers but it could be i am not picking it up. I will have to try the force testing.

 

[Qhrumphf]

I have always fermented around 10c for 2 weeks then raised it to 20c for a week before cold crashing. Would you consider this bad practice? I am fairly sure i cant taste diacetyl in my beers but it could be i am not picking it up. I will have to try the force testing.

Depends on your yeast strain. Some strains that may be about right. Others two weeks may be too late.

But.

If you're not picking up diacetyl then as far as I'm concerned there's no reason to worry about it. If it works, carry on.

 

[ListerH]

This. Start free-rising when you're 75% to your FG.

Pull it out and let it warm on its own. Don't artificially heat it.

I would say the same... I ferment my lagers in a chest freezer with external thermostat and when I want to diacetyl rest (about 25% above FG), I just turn off the power, open the top and let it naturally come up to ambient temperature which in my garage is about 10-12 degrees above fermentation temp.

 

[njohnsoncs]

This. Start free-rising when you're 75% to your FG.

Pull it out and let it warm on its own. Don't artificially heat it.

Once you're at your FG, give it another 2-3 days and start checking it. Don't worry about the temp it actually reaches.

Better than simply sampling it, do forced diacetyl testing. https://spikebrewing.com/blogs/ask-a-pro/an-easy-diy-diacetyl-test

That test will not only highlight diacetyl but metabolize its precursors INTO diacetyl. If after doing that you don't perceive it, you're good to drop temp whenever you want.

And as long as you're not fairly diacetyl blind (which a significant number of people are, my personal sensitivity is on the low side and took a LOT of work to train it), it's as effective as actual lab testing for VDKs. If you're a super-taster for diacetyl, perhaps even more effective.

Why should I not artificially heat it? That seems like a really popular way of doing it. What are the downsides?

 

[Qhrumphf]

Why should I not artificially heat it? That seems like a really popular way of doing it. What are the downsides?

You don't need to. Especially not at homebrew scale. The thermal mass is small enough that it'll warm plenty quickly on its own. In that sense, just a waste of energy.

Plus if your system isn't super fine tuned you can very easily overheat it. The temps near the heat source can rise far too much before the temp probe picks it up.

Plus whenenever possible, active yeast should have a slow, gentle temp change. Thermal shock is bad.

It's *probably* not gonna hurt to artificially heat it up, but it's not necessary and there are somes risks, with no real benefit.

 

[Home_alone1]

The reason I artificially heat is my freezer I ferment In is in an unheated garage , and I like to brew in the winter if I don’t have the heater my beer would eventually get into the 20-30s sometimes . When I have brewed in the summer before I just unplug the heater .

 

[Qhrumphf]

If ambient is too cold, then that's another story. At that point applying heat is more necessary.

However you still have to be really careful heating. A delay between heat and registering on a temp probe spells bad news. Either heating in the middle and probe on the outside (Brewjacket or coil) or heating on the outside and probe in the middle (heat wrap or pad) is asking for problems since area by the heat source will be well hotter than the probe. And if you put the probe right next to the heat source, then you'll be cycling a lot and may never hit your target.

I suppose I'd use a water bath that could be recirculated to maintain consistency of temp with the water heated, not the beer directly.