First AG Batch Is Approaching!

[BMWillis]

After a couple Mini Mash brew days, I've decided to take the big plunge!

Just put in an order for a shiny new kettle, and a few odds and ends to make my Rubbermaid cooler a legitimate mash tun. Couldn't be more excited!

Anyway, I scrubbed out my cooler a little earlier in anticipation of the weldless ball valve thats on its way, and I decided to do a little experiment. During most of my PMs, I always lost more temperature than I thought I should. On average around 5 degrees F. After I finished cleaning it today I decided to fill it with 3gal of 128 degree F water, throw the lid on it, and walk away. I re-read the temp after and hour and the water had dropped down to 122.6 degrees F, so all in all I lost 5.4 degrees.

Is that about normal?

Will adding a decent amount of grain (~8-10) pounds of grain to the mash further insulate it, leading to smaller temperature drops?


I know a lot of the All Grain process is learning how your equipment operates. I'm just a little giddy waiting for all my stuff to show up to my door, so I thought I'd get a head start on learning the piece of equipment I do have!

Also, once I nail down about how many degrees I lose in a typical 60min mash, should I add that much to my strike water temp?

 

[jfk69]

I preheat my mash tun by heating up my first sparge water, then dumping it in the tun while I heat my strike water. When the strike water is ready, I dump the water from the tun into my HLT. I only lose 1-2 degrees in the mash tun by doing this since the strike water isn't wasting energy bringing the tun up to temperature while also trying to heat the grain. Works great.

 

[johngaltsmotor]

My Igloo 10g water cooler loses about 2F over a 60-75min mash. I've taken to putting a blanket on the lid which helps (it used to be 3-4F).

When you say you filled it with 128F water and walked away - was that the water temp going into a cold cooler? Or a pre-heated cooler? Or was the water 128F after it equalized in the cooler for a while?

Adding grain doesn't help insulate, but it will provide more thermal mass - you need to lose more heat energy to drop the temperature of water + grain than of just water. 40lb of hot water vs 50lb of water +grain - the same energy loss means the grain will still be warmer.

You want to determine how many extra degrees to add to your strike water based on the stable temp about 10min after dough-in. If you still lose 5F over 60min you can decide if you want to split the difference then (it depends how spot on you feel your recipe needs to be, I normally don't worry about missing temp by 1-2F).

 

[kombat]

One trick I use to help maintain temperatures is to cover the grain bed with a sheet of aluminum foil after doughing in. Lay it shiny side down. This will help it hold heat.

Punch a few holes in the foil with your temperature probe so that when you start to recirculate/vorlauf, the wort being returned to the tun will splash onto the foil then trickle down through the holes, resulting in less disruption to your grain bed than if you were just dumping the wort directly onto it.

 

[BMWillis]

Completely forgot to pre-heat the tun before I did my little experiment. I'll have to re do it before work today, losing a couple degrees doesn't bother me too much, but 5 seems to be killing my perfectionist ways

The 'blanket on the lid' and the foil ideas are also really good, thanks guys!

 

[mgortel]

I know a lot of the All Grain process is learning how your equipment operates. I'm just a little giddy waiting for all my stuff to show up to my door, so I thought I'd get a head start on learning the piece of equipment I do have!

Also, once I nail down about how many degrees I lose in a typical 60min mash, should I add that much to my strike water temp?

Glad your giddy....we all were ....and still are when waiting for brewing supplies, matrerials, or brew day.

You are probably only losing 1 degree from your starting STABLE temperature during the 1 hour.....part of that large temperature drop is the initial heat being absorbed by the colder mash tun to bring it up to temperature......so you need to account for that initial heat loss.

Your temperature situation is best resolved using a program like Beersmith. If you do not have Beersmith I strongly recommend it. Temperature adjustments are not as simple as one-to-one increases in temperature. There are many variable.....and you must have an accurate starting point.

Required temperature of the strike water to reach target mash temperature depends on your mash tun, how much weight in grains, how much water being added, starting temperature of mash tun and grains.

With Beersmith you can set up your brewing equipment specifications. Once you nail down your equipment specs the program will calculate the strike water temperature required to reach your desired mash temperature (based on your grain bill, water-to-grain ratio, starting temps, etc.)

If you have Beersmith then you know about the following...if you need help calibrating equipment in Beersmith let us know.

For example:
1) You will specify the weight and specific heat value of your mash tun in the equipment profile. THis allows the software to calculate how much heat will be absorbed from your strike water by the mash tun. This is the biggest unknown for you starting out....but it is easy to determine this by running an experiment BEFORE brewday to make sure you have the right combination of weight and specific heat for your tun.

2) You will specify your boil off rate for your kettle. ( i.e. 1.0 gallons per hour....or 1.25 gallons per hour). THis will allow program to ACCURATELY calculate your pre-boil volume to get you your desired FG after boiling. (You probably know this already since you are not totally new to brewing)

How do you determine this. Simple......boil some plain old water in your kettle....start with maybe 5 gallons.....and boil for an hour....measure after 1-hour and you will know how much water you will boil off per hour. Make sure you note where your gas control knob is so that you can be consistent (i.e. if you open gas more on brew day....then you did in experiment....you will add more heat and boil off faster.) Your actual boil off rate may be slightly different on bre day since you will be boiling wort not plain water...but you will be dam close....and can make adjustments for next batch if needed.

Let us know how it goes. There are other good programs out there besides Beersmith....but that is what I use.

 

[EarlyAmateurZymurgist]

I never preheat my tun. I merely add four to six degrees Fahrenheit to my strike liquor temperature to account for the heat absorbed my Igloo cooler. I have also traditionally mashed-in by adding the strike liquor to the grist, not dumping the grist onto the strike liquor. Adding strike liquor to the grist affords for finer mash temperature control. Recently, I started mashing-in by underletting the mash bed, that is, I fill the tun via the drain after floating the grain onto the false bottom. I picked this technique up from a British brewing forum. Underletting significantly reduces the number of dough balls that one has to break up while mashing-in.

While one can just plug numbers into a one of the mash temperature calculators on the web, not much is learned by doing so. Here's an easy to understand formula for calculating strike liquor temperature:

Twenty pounds of grain has as much heat capacity (a.k.a. specific heat) as one gallon of water; therefore, a pound of grain has as much heat capacity as 0.05 gallons of water (1 / 20 = 0.05) or 0.2 quarts of water (1 / 20 x 4 = 0.2).

strike_liquor_temperature = ((desired_strike_temperature x (0.2 x grist_weight_in_pounds + strike_liquor_volume_in_quarts)) - (0.2 x grist_weight_in_pounds x grist_temperature)) / strike_liquor_volume_in_quarts

Note: additional parens were added to improve order of operations clarity

Example:

grist_weight_in_pounds = 10
grist_temperature = 72
strike_liquor_volume_in_gallons = 12.125 (1.25 quarts per pound)
desired_strike_temperature = 151


strike_liquor_temperature = ((151 x (0.2 x 10 + 12.5)) - (0.2 x 10 x 72)) / 12.5 = (2189.5 - 144) / 12.5 = ~164F (actually 163.64)

In practice, depending on how full one's mash tun is after mash-in has been completed, it will take an additional 4 to 6 degrees Fahrenheit to hit one's target mash temperature due to thermal losses, which is why a good strike liquor temperature for a 151F mash is around 169 to 170F when using a hot liquor to grist ratio of 1.25 quarts per pound in a non-preheated cooler-based mash tun.


The formula shown below is mathematically derived from the equation shown above. It is based on a strike liquor volume to one pound of grist ratio. This ratio holds as we increase the weight of the grist; therefore, the result holds as we scale the grist.

strike_liquor_temperature = (.2 / hot_liquor_to_grist_ratio_in_quarts_per_pound)(desired_strike_temperature - grist_temperature) + desired_strike_temperature

grist_temperature = 72
hot_liquor_to_grist_ration_in_quarts_per_pound = 1.25
desired_strike_temperature = 151

strike_liquor_temperature = (.2 / 1.25)(151 - 72) + 151 = 12.64 + 151 = 163.64

As one can clearly see, the second equation produces the same result as the first. However, it trades clarity for brevity. If anyone wants to see how formula two is derived from formula one, just let me know.

 

[BMWillis]

Thanks for the responses guys!

I've definitely started to play around in BeerSmith to set up my equipment profile. Got as much done as I can. As soon as I get my kettle from Spike I can figure out my boil off rate and take if for a spin with a house Blonde brew day.

The math is also really interesting, and really helped me wrap my head around it.

I ran my little test again with a pre-heated mash tun and a blanket on the lid and only lost 3 degrees. With a thicker blanket I'm pretty sure I can get it down to 1 or 2!


Sent from my iPhone using Home Brew

 

[EarlyAmateurZymurgist]

Are you testing how long the tun will hold temperature? Or are you testing the temperature drop after adding hot liquor? Adding a blanket to the top is not going to reduce the initial temperature drop that is experienced after adding hot liquor. That drop is caused by the tun sinking heat until it equalizes with the temperature of the liquor. Pre-heating helps because it reduces the temperature differential between the tun and the strike liquor. However, the grist will also sink a small amount of heat during mash-in.

 

[kh54s10]

Pre-heating takes some of the guess work out of what temperature your strike water needs to be. In the winter my mash tun is on the porch at ambient temperature. I usually wait for 40+ degree days. If it is 90 degrees a lot less temperature drop will happen as opposed to 40 degrees.

 

[BMWillis]

Are you testing how long the tun will hold temperature? Or are you testing the temperature drop after adding hot liquor? Adding a blanket to the top is not going to reduce the initial temperature drop that is experienced after adding hot liquor. That drop is caused by the tun sinking heat until it equalizes with the temperature of the liquor. Pre-heating helps because it reduces the temperature differential between the tun and the strike liquor. However, the grist will also sink a small amount of heat during mash-in.

I was just trying to see how well it held the temperature. I know that initial drop will happen, but that's where the math and BeerSmith will hopefully help me out a little!


Sent from my iPhone using Home Brew

 

[johngaltsmotor]

I may skip the pre-heat now to save water. I end up using 168F strike to hit a stable 154F mash but lately I've had to add cool water as my strike goes over temp ("manually" regulated propane burner). I might as well just compensate with hotter water instead of trying to preheat which seems less predictable.