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Dead Space?
Anyone know what this is? I heard that too much in a mashtun is a bad thing..........
The deadspace is the amount of area that the mash is NOT displacing. It isn't so much as it is a bad thing, as much as it is inefficient, and loses heat a lot easier. Picyure a full DD cup of coffee. It can stay hot for an hour. Remove the lid and maybe stay hot for 45 minutes. However drink 2/3 of the cup, and the remaining 1/3 will only stay hot for a few minutes. When trying to hold a mash temp for 60 minutes, it may make it difficult if you do not have close to a full tun.
Perfect! Thanks Thirsty...that's what I thought it was.....I have way too much headspace, which would explain the difficulty I've had maintaining mash temps....I'm using a 54 qt rectangular cooler, and still only doing 5 gallon batches. I could easily do a 10 gallon batch....
Now that I think of it, or think at all to start(!)....I remember you saying a sanitized piece of foam or something like that would help...from another post.....
Crap! I just threw out a bunch of foam stuff....oh well, now I know for sure...
Cheers!
Without doing something to void that headspace, there are a few options.
1. Overshoot your mash temp by maybe 4 or 5 degrees, and stir the hell out of it to get the quick heat loss out, and it will probably hold a little longer
2. Overshoot by a couple degrees and hope that the temp drop stays within the desired mash temp for the first 20 minutes (majority of conversion happens here anyway)
3. Build a HERMS or RIMS then you can do the opposite, start low for beta conversion, then ramp up later for alpha conversion, then hit MO temps perfect
4. Switch to 10 gallon batches (highly suggest) there really is no time difference on brewday, besides heating the boil and strike/sparge water
I always screw up my mash temps by a degree or two....and I know that's a bad thing. I guess I have trouble figuring out exactly how hot the strike water has to be, based on the 1.25 ratio of grain/water......There's so many different calculators for it, I tend to use a mix of all of them, and see what happens....I know, bad and inconsistent.........someday, I'll figure it all out perfectly.......
I always calculated deadspace as the amount of area that the wort or water won't come out of the vessel you are using (sparge tank, Mash tun, and boil kettle)........eg. my mash tun has a deadspace of .25 gallon.......
This is from my BeerSmith equipment page and as you can see it's for a 5.25 gallon batch using a 10 gallon cooler......
Brew Pot (12.5 gal) and Igloo Cooler (10 Gal)
Batch Size: 5.25 gal
Mash Volume: 10.00 gal
Boil Volume: 7.28 gal
Mash Tun Weight: 9.00 lb
Evaporation Rate: 18.00 % Mash Tun Specific Heat : 0.300 cal/g-deg C
Boil Time: 60.0 Mash Tun Deadspace: 0.25 gal
Top-up for Boiler: 0.00 gal Equip Hop Utilization: 100.00 %
Losses to Trub/Chiller: 0.50 gal Cooling Loss (%): 4.00
Top up water for Fermenter: 0.00 gal
and I very rarely have missed my temperatures.........the way to figure it is to fill it with water and drain and then pour what's remaining in a jug so you can measure it
Read this...... http://www.brew365.com/technique_calcul … volume.php
Would preheating your mash tun help make up for the dead space?
FirePitBrew wrote:
Would preheating your mash tun help make up for the dead space?
I heard it may help to prevent initial loss of temperature. Last time I brewed, I put a few gallons of hot water in right away to "pre-heat" the mashtun. Once the strike water was ready and the grains were crushed, I drained what was in there, and added the new water and grains. I noticed the temp didn't drop as much as the first time I used the same MT...only a few degrees, but certainly a difference....
FirePitBrew wrote:
Would preheating your mash tun help make up for the dead space?
Preheating the tun will certainly lessen the loss to headspace above the mash, but it doesn't eliminate it.
The problem with coolers as mash tuns is that they are really meant for keping things cold. Cold air sinks right, so all the insulation in a cooler is in the body of the cooler. There is usually no insulation the lid (probably a cost and profit margin issue) and that makes sense because of the nature of cold air sinking. But when you put hot mash in there all that heat wants to rise up and out of the tun. So with an uninsulated lid the lid conduct that heat out in to the environment.
I deal with that issue but putting two heavy spare bath towels on the top of the tun. This keep the lid insulated pretty well and I only loose a degree at best to through the lid. I do this regardless if the cooler has a small mash (large headspace) or a large mash (no heaspace).
So preheating helps you from not having to reheat the deadspace lids and walls, but it doesn't eliminate the air that needs to be reheated once you onpen and close the tun. Insulateing the lid makes that more effiecient too.
dartgod wrote:
I always calculated deadspace as the amount of area that the wort or water won't come out of the vessel you are using (sparge tank, Mash tun, and boil kettle)........eg. my mash tun has a deadspace of .25 gallon.......
I kind of agree with Dartgod here I treat the term deadspace as the volume I can't physically extract. In my lab at work we also refer to it at "Void Volume".
I'm getting conufused.....I thought deadspace was just the area not being used by the actual grist in the MT itself. When I drain my MT, I let it go all the way, check the total volume I got out, make any adjustsments to my sparge total, and let it go with that.....
So, If I have a 54qt cooler, and I put in 10 lbs of grain with 12.5 qts of water...what is my deadspace? It only fills the MT a little less than halfway...but I plan on extracting as much as I can, as close to the full 12.5 qts to go to the boil.....or am I maing no sense now>?.......
:needabeer:
The deadspace will be the amount of liquid that won't come out of your mashtun when it's completely drained due to the inabiltity of your braid or falsebottom to extract all the liquid.......headspace is the amount of area in your tun above the mash that's not used.......
I don't preheat my tun because my calculations are fiqured for the tun being at room temperature.....the software (BeerSmith) also allows for preheating the tun to be added into your calculations if you like......it sure makes it alot easier than doing it by hand........it's sort of like doing math in elementary school, it's nice to learn to do the calculations by hand and to understand why you are getting the answers you do but as you get into Jr. and Sr. High it's more important to get some work done so you just use a calculator ......
Ahhh...okay, that makes sense, sort of.....
So I use a long SS braid, and after I drain the MT, if I were to use improper methods to get more out of the MT, that volume would be the deadspace volume, as in I could put say 3 gallons in, and only get 2.75 out, I would have .25 gallons of deadspace??.....
Exactly.........some mashtuns due to manifold design or falsebottoms sitting up off the bottom may have a half gallon or so they can't drain.......the more the worse the design or efficiency of your system, although when draining your tun the last little bit coming out isn't going to have that much sugars left in it as it will be at the last of your sparge........
Brewchez wrote:
Preheating the tun will certainly lessen the loss to headspace above the mash, but it doesn't eliminate it.
Ah, gotcha. I was mixing up head space and dead space. I need to go back and read the All Grain sections of all the books I've read and didn't understand the first time around when I started brewing. First all grain is right around the corner..
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