I would like to know what the reason is for haing vent fully open when doing poultry (chicken in my case). I know it relates to humidity but I don't know what the effect on the bird is of having vent open as oposed to 1/4 or so open.
Science lesson please :)
One reason is because you want to let the moisture out quickly. Especially when doing yard bird. You can get condensation build up by the vent and have it drip down back onto the food.
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Quote from: mikecorn.1 on October 20, 2011, 11:31:28 AM
One reason is because you want to let the moisture out quickly. Especially when doing yard bird. You can get condensation build up by the vent and have it drip down back onto the food.
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So the reason is to not get drips on bird? Could that not be avoided by a catch can above bird?
My reason for asking all of this is that I can't seem to get temp up, sitting at 200F, with vent fully open so looking trying to figure out if I can get by with vent not fully open.
I guess there is always the trial and error way but if the answer is already out there ...
I read on one thread here recently that when you close the vent, the actual moisture in the cabinet will rob you of heat in due to something
I can't explain cause I'm supposed to be working and I'm on the forum again. :D. You low temps could be
Caused by other factors like wind, loose connections or even using an extension cord or non dedicated outlet to the Bradley.
Others should be by to bail my butt out of this one :) have to get back to work :D.
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I would keep the vent open a minimum of 3/4. The moisture will absorb a lot of your heat if not open enough. If you are not in a windy environment, the bird is at room temp or higher, and your unit is set for maximum heat output, then perhaps something is wrong with the unit. Are you using an extension cord?
I've actually wondered that myself at times, especially after running the numbers – so to speak. Most chicken has been enhanced and has a higher moisture content than non-enhanced chicken. A raw chicken is about 66% water - and adding 15% enhancing will take that up to over 70%. However, ironically, the weird thing is that beef is usually in the above 70% range, brisket is 71% and loses more in cooking - down to mid 50%, Chicken doesn't lose as much - it finishes off usually in the very low 60%. Pork and Venison usually have even a little more water content in the raw meat. Generally leaner meats have more water content than fatter meats. So why does chicken have more of a problem? I don't know – I wish I did.
However, the thing about moisture in the cooking chamber might be explained as follows. It has to do with entropy and thermodynamics. The more moisture in the air, the more heat it takes to heat up the air. It is the heat capacity of the air. Wet air has a greater heat capacity than dry air. Probably because the moist air is between the heat source (element) and the meat it (the moist air) probably absorbs a good bit of the heat before it can get to the heat. But that is not necessarily a bad thing – once heated, the heated moist air also has more conductivity and more molecules (denser) than dry air and therefore should theoretically cook the meat faster because of more hot molecules with faster heat transfer hitting the meat. Uhhhh – can I say Texas Crutch (uuggghhhh – now I have to go wash my mouth out with soap).
One of the two bad things about overly moist air in the Bradley is the aforementioned "black rain". The moist air condenses on the inner cabinet surface, dissolves a little soot and smoke resins and drips onto your meat – not a particularly pretty sight – but not a "throw it away or give it to the dog" problem. The other and worse problem is that water vapor backing up into the smoke generator and then condensing. That has a higher probability of being a bad thing. Condensation and moving parts and electricity don't mix so well. That air and moisture has to go somewhere, and it is best it not go through the generator.
Most experienced Bradley smokers will say their vents are stuck in the fully open position or just a little less. You are not going to lose much heat with it being open.
As already said many other factors can cause the heat to be low, including blocking the heat by a low rack location of your meat. In an OBS the thermometer is located in the top 1/4 of the cabinet. If you have two butts on a rack below the thermometer, they may be blocking the heat from rising to the thermometer. There has been a lot of wind lately, that will suck the heat out. Or how much meat you put in will definitely affect how fast the Bradley recovers heat.
I would do what Wildcat suggested, and close the vent to 3/4 open.
You didn't mention how large of a load you are smoking/cooking. That will also make a difference on how the smoker functions, but as you get closer to the finished internal temperature you should see some improvement in cabinet heat. Also you didn't mention what type of unit you are using and your heat settings.
The guideline is for chicken with skin, that is were a great deal of the moisture is located. Whether the poultry is enhanced or not, it will loose about the same amount of moisture. Cook's Illustrated did a test on brined and unbrined chicken and found that both lost about the same amount of moisture, but because the brine chicken started with more moisture, it had more moisture left in the meat.
To add to Caney's explanation, my understanding is that it takes a lot of heat energy to convert liquid into steam. If that steam is trapped and can't escape the air becomes too saturated and the steam condenses. Once this occurs the air becomes drier and able to hold more moisture, thus more heat energy is used to convert the condensed liquid into steam again. This is how vertical water smokers are able to keep lower temperatures.
Well, a science lesson was asked for and presented as Caney's second and third laws of thermodynamics - or was it the first and third? ;D Seriously, I mean no disrespect; all good information.
I was of the same mind when I first started. Put some heat in a box. OK. Make a hole in the top. It must let heat out. Close the hole to keep the heat in. Seems to make sense.
I guess the best I can do is to state that the hole in the top will let out both moisture and heat. But, letting out the moisture component is worth it. Steam, or very humid air will hold the temp down.
Also, keep the vent area clean or you will experience 'black rain'. A side-mounted stack would leak down the inside or outside of a smoker but this goes right on top.
Quote from: ArnieM on October 20, 2011, 03:29:12 PM
Well, a science lesson was asked for and presented as Caney's second and third laws of thermodynamics - or was it the first and third? ;D Seriously, I mean no disrespect; all good information.
I was of the same mind when I first started. Put some heat in a box. OK. Make a hole in the top. It must let heat out. Close the hole to keep the heat in. Seems to make sense.
I guess the best I can do is to state that the hole in the top will let out both moisture and heat. But, letting out the moisture component is worth it. Steam, or very humid air will hold the temp down.
Also, keep the vent area clean or you will experience 'black rain'. A side-mounted stack would leak down the inside or outside of a smoker but this goes right on top.
What Arnie said.
I approach this from my old firefighting days. If you have a fire inside a building you use a fog nozzle and whip it around a few times and the fire generally goes out. Why? ....... Because you have cooled the fire to below its ignition temp. Hold on there Bucko you say......aren't you smothering the fire with water? Nope! You are converting very small droplets of water into steam. Steam then cools the fire. In early firefighting they used a "steam engine" and sprayed steam on flames. If you have ever witnessed a structure fire you see dark smoke when the fire is raging. The fire department shows up and attacks the fire and then you see the dark smoke turn to gray then to white which is steam. The guys are getting the fire under control when you see the white smoke (steam).
When you have a smoker that has a lot of moisture the heating element is trying to convert the moisture into steam and sucking the energy from cooking the meat. Open the vent and allow the moisture to escape will allow more heat to build to cook the meat. Next time you start a smoke take a piece of paper towel and hold it above the vent and see how long it takes to get the paper towel damp. This is from moisture escaping. Bottom line is more moisture in the cabinet means less heat. Less moisture means more heat.
Full disclosure.....my vent is stuck in full open ;D
Quote from: Sailor on October 20, 2011, 07:28:30 PM
I approach this from my old firefighting days. If you have a fire inside a building you use a fog nozzle and whip it around a few times and the fire generally goes out. Why? ....... Because you have cooled the fire to below its ignition temp. Hold on there Bucko you say......aren't you smothering the fire with water? Nope! You are converting very small droplets of water into steam. Steam then cools the fire. In early firefighting they used a "steam engine" and sprayed steam on flames. If you have ever witnessed a structure fire you see dark smoke when the fire is raging. The fire department shows up and attacks the fire and then you see the dark smoke turn to gray then to white which is steam. The guys are getting the fire under control when you see the white smoke (steam).
When you have a smoker that has a lot of moisture the heating element is trying to convert the moisture into steam and sucking the energy from cooking the meat. Open the vent and allow the moisture to escape will allow more heat to build to cook the meat. Next time you start a smoke take a piece of paper towel and hold it above the vent and see how long it takes to get the paper towel damp. This is from moisture escaping. Bottom line is more moisture in the cabinet means less heat. Less moisture means more heat.
Full disclosure.....my vent is stuck in full open ;D
Well said!
Moisture absorbs the "energy" of the heat,,,,,,,,,,,less moisture= more heat.
In an electric smoker that is, a wood fired smoker produces its own moisture as even aged wood still contains approximately 20% moisture.
Quote from: ArnieM on October 20, 2011, 03:29:12 PM
Well, a science lesson was asked for and presented as Caney's second and third laws of thermodynamics - or was it the first and third? ;D Seriously, I mean no disrespect; all good information...........
To be fair to Caney, and as you pointed out Nizztos did ask for a scientific answer.
Not everyone, but a lot of people do like to know some of the science behind cooking. I'm one of those people, and would not want to discourage others from asking similar types of questions. To me it makes it a little more fun, and makes me feel like I can control the cooking process better.
Thanks a bunch!!
And yes I too like to know a bit about the science behind what goes on. My favorite cooking show is Blumenthals series of shows explaining why things are done the way he does them.
Given that I only did one small chicken (they are about 3# in my part of the world) I still think I will experiment with closing the lid a bit as I saw no signs of moisture this time. The test with a paper towel at ent sopunds like a good idea.
Also, there is a slight chance that we have less water in our chickens due to different regulations, i.e. our producers can't get away with adding the same amount as yours can. I would not bet all my money on that one though and even if that was the case there would still be a fair bit in them.
Also keep in mind that the area you live in can also have an effect. If you live in a place with high humidity the it will be more difficult for that moisture to be removed then a dryer area where I live for example. Being these smokers are mostly located outside then mother nature is also something that you must take into consideration also.
Quote from: Sailor on October 20, 2011, 07:28:30 PM
I approach this from my old firefighting days. If you have a fire inside a building you use a fog nozzle and whip it around a few times and the fire generally goes out. Why? ....... Because you have cooled the fire to below its ignition temp. Hold on there Bucko you say......aren't you smothering the fire with water? Nope! You are converting very small droplets of water into steam. Steam then cools the fire. In early firefighting they used a "steam engine" and sprayed steam on flames. If you have ever witnessed a structure fire you see dark smoke when the fire is raging. The fire department shows up and attacks the fire and then you see the dark smoke turn to gray then to white which is steam. The guys are getting the fire under control when you see the white smoke (steam).
When you have a smoker that has a lot of moisture the heating element is trying to convert the moisture into steam and sucking the energy from cooking the meat. Open the vent and allow the moisture to escape will allow more heat to build to cook the meat. Next time you start a smoke take a piece of paper towel and hold it above the vent and see how long it takes to get the paper towel damp. This is from moisture escaping. Bottom line is more moisture in the cabinet means less heat. Less moisture means more heat.
Full disclosure.....my vent is stuck in full open ;D
Wonderful short example of the science behind it all that everyone can grasp. Very well stated Sailor.
Like Habs, I also like knowing the science behind things, especially when it comes to food preparation.
However, in a Bradley you are probably dealing with water vapor and not steam. Steam is just water vapor that is above the boiling point. Until well into the cook does the temp of the meat gets past the boiling point and even then only at the surface or near the surface. So up until then the moisture is due to evaporation and is water vapor. And if your CT is 200 or 220, you aren't making much if any steam. Moist air can hold a lot more heat than dry air. Maybe it absorbs more of the limited heat that the element puts out than dry air does.
or maybe
Dry air can get hotter than moist air because it doesn't contain the water that must change states before it can get hotter.
This has become a very interesting topic. I am not a scientist and sure wish I knew the answers. Here are some things to think about. If it's true that water boils and creates steam at 212 degrees then would it not make since that steam is being created in a smoker if the cabinet temp is greater than 212 degrees?
It is my understanding that steam is considered a gas and water vapor is just tiny water particles suspended in the atmosphere. So if this is true then would it be true that a smoker is producing both steam and water vapor? If water and water vapor changes to a gas at 212 degrees then would it be true that the vent is ejecting steam and not vapor when the cabinet temp reaches 212 degrees?
We have humidity that we are also dealing with. As 1 cubic foot of heated air/smoke is taken out of the cabinet we are replacing that cubic foot of air with ambient air that hold the current humidity. Is humidity considered to be water vapor? If this is true then the cabinet does have water vapor being introduced all through the cook. Remember the water pan has water that is heated and producing water vapor also.
It takes 1,334 BTU's are required to raise 1 gallon of water from 40 degrees to 200 degrees Fahrenheit. So would it not be true that it will take less BTU's to heat a cabinet that has meat put in at 77 degrees? Would it not be true that if the meat temp comes up to 100 degrees it will take less BTU's to get the meat to 200 degrees. If this is all true then would it be true that to heat up and maintain a cabinet temp of 225 degrees it is best to eject as much water vapor and steam as quickly as possible?
If the cabinet temp is 225 and the exterior of the meat is 190 degrees with an IT of 140 degrees are we producing steam in the meat. I would think not since the meat is not at boiling point. Would it be true that the meat is creating water vapor at the above temps? I would think so as the water is evaporating and becoming water vapor. If this is true then again would the water vapor coming off the meat turn into a gas as the cabinet temp is above 212?
My head hurts and I need a beer :o
'latent heat' may have something to do with it.
http://www.splung.com/content/sid/6/page/latentheat
In this case the additional energy required to cause the phase state transition of the moisture in the cabinet to a gas (steam).
The definition of steam has come up before. We commonly think of steam as a product of boiling water, but as phild pointed out the term steam is used for water in it's gaseous state, so water that evaporates at any temperature produces steam, and can raise the RH level of the air.
Depending on the temperature of the air will determine how much moisture it can hold before condensation begins. If the steam cannot escape then condensation will begin, once condensation begins, it takes more energy to convert the condensation into steam, so the heat goes toward converting water into steam, instead of heating the air.
Long story short, just keep the @#&% vent open!
Just kidding,I also enjoy the scientific explanations.
I really think I need to experiment a bit. I can be a bit contrary when all the pieces of a puzzle is not in front of me ....
We decided that vent has to be open to keep temperature up. But it seems to me that we came to that conclusion based on what water does to temperature. Not what the chicken does to temperature. I.e. how do I know that the chicken releases enough water to make the arguments valid? (my missing piece of the puzzle)
One of these days I will buy a couple of frozen chickens that I thaw and cook one at a time with vent fully open and less open to see if temperature is affected (by a single chicken).
It is not obvious to me that a single chicken would release more water than a cabinet filled with buts for instance.
American chickens seem to be way larger than ours though, from reading recipe posts, so that could make a difference.
Here is the honest truth behind the science...
When the vent is fully closed the Bradley Gnome(Who lives in every Bradley) will get really scared and start breathing heavy. He likes the small amount of light he gets from the vent being open when the cabinet door is closed. This heavy breathing and perspiration causes excessive moisture to build-up in the cabinet. And without the vent open he gets really scared causing more sweating and heavier breathing. By opening the vent you alleviate his fear and allow the rest of moisture to escape out the vent.
This may sound very far fetched but the fact is you cannot argue with science! ;D
Quote from: muebe on October 21, 2011, 09:42:21 PM
Here is the honest truth behind the science...
When the vent is fully closed the Bradley Gnome(Who lives in every Bradley) will get really scared and start breathing heavy. He likes the small amount of light he gets from the vent being open when the cabinet door is closed. This heavy breathing and perspiration causes excessive moisture to build-up in the cabinet. And without the vent open he gets really scared causing more sweating and heavier breathing. By opening the vent you alleviate his fear and allow the rest of moisture to escape out the vent.
This may sound very far fetched but the fact is you cannot argue with science! ;D
LOL
Does that make other food than poultry comfort food then :)
PS It is true that the full open thing applies to poultry only? Or did I miss something?
my vent has been wide open from the first day.
Nizztos;
You are right. One chicken with skin, may not make that big of a difference. I always adjust my vent according to what I am cooking and how large the load, but with any amount of chicken with skin I always start with 3/4 open and adjust from there. During the cooking occasionally I will hold my hand over the vent to check the moisture. Checking the moisture this way takes a little practice, but after a few tries, you will see that you can hold your hand over the vent longer when air is dryer, then when it is saturated with moisture; even though the cabinet temperature is the same during both tests. As the air feels dryer I will slightly close the vent.
I do know that cooking chicken with skin absolutely will bring your cabinet temperature done more the whole muscle meats. Skin has a lot of moisture. My thought is that moisture from the skin will release easier and faster than the moisture that is trapped in the cells of a 8 pound butt, or a 10 brisket.
Large loads generally will produce a lot of moisture, picnic shoulders or hams with skin on will also produce a lot of moisture in the cabinet.
Quote from: GusRobin on October 21, 2011, 01:43:55 PM
Long story short, just keep the @#&% vent open!
Just kidding,I also enjoy the scientific explanations.
;D ;D ;D ;D ;D
Hmmm now you got this old country boy confused. I was always taught to raise the humidity in a house in the winter. This is because moist air heats quicker and holds more heat. If so it causes you to be warmer. This is what I thought all these years.
First problem I had with the Bradley was it wouldn't heat enough while doing a load of ribs. Found out I had to open vent all the way. Then it proceeded to warm up.
Ok in a simple basic language could some body tell me whats wrong and why with my theory. I'm not calling anyone wrong or me right. Just a little thick skulled some times. And I want to understand.
Generally, one wants to not let the air in the home get too dry in the winter. Heat (gas, wood, coal, oil, etc. in particular) tends to get the air so dry that many (including myself) have sinus problems and nose bleeds. In high heat and humid environments we tend to feel the heat more. Likewise in a cold humid environment we tend to feel the cold more. At the same time, the moisture in reality actually helps to moderate the heat and cold. The desert is very hot, but the Gulf Coast feels hotter and and more stuffy at the same temp due to the higher humidity. In the desert communities many people have swamp coolers vice air conditioners which is basically air being forced through water vapor. The water absorbs the heat in a dry environment and cools the air which is forced into the home.
Quote from: viper125 on November 02, 2011, 01:00:49 PM
Hmmm now you got this old country boy confused. I was always taught to raise the humidity in a house in the winter. This is because moist air heats quicker and holds more heat. If so it causes you to be warmer. This is what I thought all these years.
First problem I had with the Bradley was it wouldn't heat enough while doing a load of ribs. Found out I had to open vent all the way. Then it proceeded to warm up.
Ok in a simple basic language could some body tell me whats wrong and why with my theory. I'm not calling anyone wrong or me right. Just a little thick skulled some times. And I want to understand.
Raising the RH in your house will have very little to do with your house temperature rising faster. Though warmer air can hold more moisture, the amount of moisture does not increase the heat.
In addition to what Wildcat pointed out, 70°F with 70% RH, will
feel warmer then 70°F at 25% RH. It has to do with the rate the body will perspire. The drier air makes it easier for moisture to evaporate from the skin, the faster the evaporation rate the cooler we feel. When you watch the weather you will frequently hear the weather person state it is 70°F, but will feel like 72°F. To find out more on how RH effects human comfort do a google on "heat index", that should explain it more clearly.