Triple Decoction Boil Off Rate

[ApolloSimcoe]

This upcoming weekend I am planning to do a triple decoction Hefeweizen recipe with the following rests:
Acid Rest @ 113 for 15m
Protein Rest @ 126 for 15m
Mash Rest @ 146 for 20m
Mash Rest @ 158 for 20m
Mash Out @ 167 for 10m

As I was calculating my water usage for this brew it dawned on me about boil off rates of the decoction. Anyone that's done a triple decoction before have any insight or thoughts on what I can expect? Or is this something I shouldn't even be concerned about?

Thanks for the feedback!

 

[Vale71]

It all depends on lenght and strength of the decoction boil. When I do longer decoctions (45 to 60 minutes) I add RO water to compensate for the expected evaporation loss (about 2l/hr for my system), otherwise I know I'm going to land short both on step temperature and on final volume.

 

[ApolloSimcoe]

My plan was to do a 15m boil for each step.
thanks for the input

 

[kh54s10]

The way I did my decoction it didn't matter. I scooped out the proper amount of mash for the boil, boiled it, returned it to the mash then did a normal sparge. The boil off is exactly the same as any other beer. What changes is the amount of sparge water you need. I don't pre-calculate that. I measure what is going into the boil kettle.

 

[ApolloSimcoe]

What changes is the amount of sparge water you need.

And this is what I'm looking for. An approximate of how much additional sparge water was needed to meet preboil volumes. My boil off rate is 1.5g/hr

 

[kh54s10]

I never measure that, I just make sure I have more sparge water than I need. Then measure run off and if I get 3 gallons I know I still need 4.2 more gallons of wort in the BK for my system.

 

[Vale71]

And this is what I'm looking for. An approximate of how much additional sparge water was needed to meet preboil volumes. My boil off rate is 1.5g/hr

I'd recommend compensating for decoction boil-off in the decoction itself. For longer decoctions you'll undershoot your step temperature if you have significantly lower volume at the end of decoction than what you started with.
For a boil off rate of 1.5g/hr you'd need 0.375 gallons to compensate for a 15 min decoction.

 

[ApolloSimcoe]

I never measure that, I just make sure I have more sparge water than I need. Then measure run off and if I get 3 gallons I know I still need 4.2 more gallons of wort in the BK for my system.

This is how I used to do it too. Now that I am focusing more on my water salts I thought I should be more diligent with my water usage calculations as well.

Thanks again for the feedback

 

[cactusgarrett]

I take your approach - measured amounts of sparge water (batch sparging), but then make up any drastic differences via an ad hoc, quick extra sparge if needed.

You should get around the same boil off rate - just pay attention to the weather: hot & humid is a lot lower rate. I never factored evaporation loss into my decoction brew days, then had to revamp my personal sheet to account for it, as overlooking it had me off by at least a half gallon or more for longer/numerous decoction steps.

 

[ApolloSimcoe]

thanks, I'll calculate that in. I will be boiling the decoction inside on my stove and brewing outside on my propane burners.

Just to be clear I'm not concerned about boil off rates in my brew kettle. I'm strictly asking about boil off rates while boiling the thick part of the mash.

This will be my first decoction so I'm trying to cover my bases and thinking up scenarios of what I should watch for

I'll just make sure I have that extra .5-1 gallon on hand

 

[Vale71]

hot & humid is a lot lower rate.

No, it's most definitely not. We are not talking about evaporation but about actual boiling.

 

[kh54s10]

No, it's most definitely not. We are not talking about evaporation but about actual boiling.

If you are talking of "boil off" and having liquid loss, that is evaporation, isn't it?????

 

[cactusgarrett]

No, it's most definitely not. We are not talking about evaporation but about actual boiling.

Liquid->Vapor = evaporation
Go troll somewhere else. But if it makes you feel better to use the same term throughout, sub "boil off" for "evaporation".

 

[Vale71]

I'm not trolling, I'm just responding to the nonsense you keep posting over and over again.
There is a huge difference between evaporation and boiling. Even a quick Wikipedia search will make the difference immediately apparent but it seems you cannot be bothered even with such a simple task and yet you find the time and energy to keep on spouting such uninformed bullcrap.

Here is the first couple of sentences from the Wikipedia page I linked to in case you're too tired to click on the link:

"Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor.[1] There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon."

If you could be bothered to read through the Wikipedia pages for evaporation and boiling (the links are right there in the period I quoted, it won't take much effort to click on them) you'd see immediately what nonsense you've been posting. Specifically, the factors you mentioned (and a few others you forgot to mention such as free surface area) have an influence on the rate of evaporation whereas they have no influence whatsoever on the boiling process.

 

[kh54s10]

I'm not trolling, I'm just responding to the nonsense you keep posting over and over again.
There is a huge difference between evaporation and boiling. Even a quick Wikipedia search will make the difference immediately apparent but it seems you cannot be bothered even with such a simple task and yet you find the time and energy to keep on spouting such uninformed bullcrap.

Here is the first couple of sentences from the Wikipedia page I linked to in case you're too tired to click on the link:

"Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor.[1] There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon."

If you could be bothered to read through the Wikipedia pages for evaporation and boiling (the links are right there in the period I quoted, it won't take much effort to click on them) you'd see immediately what nonsense you've been posting. Specifically, the factors you mentioned (and a few others you forgot to mention such as free surface area) have an influence on the rate of evaporation whereas they have no influence whatsoever on the boiling process.

No, it's most definitely not. We are not talking about evaporation but about actual boiling.

Well you still got it wrong. The discussion is not about the semantics between the terms of evaporation and boiling. It is about the amount of wort lost.

If just boiling, it is totally up to the amount of time that you boil, among other factors such as pot geometry, temperatures and humidity.

If you made the comparison between evaporation and vaporization then maybe it makes some sense, but still does not address what the question is about.....

 

[cactusgarrett]

I'm not trolling, I'm just responding to the nonsense you keep posting over and over again.

Didn't even have to do any of your nonsense - just defined "evaporation".
The whole point was that humidity will affect the rate of loss, but you can spin off into arguing the difference between absorption and adsorption, and I'll go back to blocking you.

 

[Pappers_]

Ok, everyone step back and take a deep breath. No personal attacks, please.

@ApolloSimcoe I decoct most of the lagers I do, and rely on BeerSmith to get me the right initial volume, which is usually a little thinner mash than without the decoction. Then I sparge until I hit the my pre-boil volume target. I am almost always either spot on or no more than a couple of points off of my target gravity and volume using that method. Using this method, you don't really need to calculate the rate at which you will boil off during the decoction, because you make it up in the sparge.

 

[passedpawn]

If you are talking of "boil off" and having liquid loss, that is evaporation, isn't it?????

Nope, it's vaporization. Vaporization happens at the element. Evaporation happens a the surface of the kettle. Two entirely different events.

[edit] I see I'm just repeating what's above, sorry about that

 

[kh54s10]

Nope, it's vaporization. Vaporization happens at the element. Evaporation happens a the surface of the kettle. Two entirely different events.

[edit] I see I'm just repeating what's above, sorry about that

No problem, I was educated on the difference between evaporation and vaporization. I really knew the difference but didn't use the terms properly.

 

[Vale71]

Apologies for having lost my cool, but in the face of stubborness I tend to reach my boiling point and blow my lid. Pun 100% intended.

For the last time then I'm done:

Evaporation and boiling are two completely different phenomena at the physical level. Semantics has got nothing to do with it, the reason they have different names is only because they are distinct phenomena at the physical level and not because someone thought the English language was a bit too succint for their taste and needed some enrichment.

The difference relies entirely on the concept of vapour pressure. Below the boiling point the vapour pressure is lower than atmospheric pressure. Vapour can only therefore escape by mixing with the surrounding atmosphere. Air has a limited capacity of absorbing water vapour dependent on pressure and temperature and that's where the concept of relative humidity comes into being. Since you cannot have more then 100% relative humidity once you reach that point no further evaporation can occur or if it does then condensation will take place in the oversaturated atmosphere.

Once the boiling point is reached vapour pressure will equal atmospheric pressure and therefore water vapour will be released without needing to be absorbed by the atmosphere. As a matter of fact water vapour can and will displace the surrounding atmosphere once it breaks the liquid surface. This is exactly what happens in a pressure cooker or autoclave once the pressure relief valve starts venting. Given enough time the atmosphere inside the vessel will be made up of 100% water vapour with no trace of air at all.

Boiling will continue as long as heat is applied to the liquid and in a perfect world the rate will only be determined by the amount of heat per unit of time supplied to the liquid by the heat source divided by the vaporization enthalpy of water (which is only dependent on pressure, so that on mount Everest boil-off rate does indeed increase albeit only infinitesimally). In the real world you'll always have heat losses and those will reduce actual process yield to less than 1.

Long story short, they are different processes and the factors driving and influencing them are different too. Mixing them up willy-nilly is factually wrong and misleading.

 

[ApolloSimcoe]

I decoct most of the lagers I do, and rely on BeerSmith to get me the right initial volume, which is usually a little thinner mash than without the decoction. Then I sparge until I hit the my pre-boil volume target. I am almost always either spot on or no more than a couple of points off of my target gravity and volume using that method. Using this method, you don't really need to calculate the rate at which you will boil off during the decoction, because you make it up in the sparge.

This was helpful, thank you. I plan on doing a thinner mash than usual (2qts/lb)