Hi,
I've been reading this forum and it has helped me brew some nice beers and troubleshoot several issues, so thanks to all!
There is one subject that I think I can contribute to; cooling wort.
This is the info I've gathered so far on cooling wort;
1.- Luke-warm wort is at the highest risk of bacterial contamination (think of leaving a potato salad at room temperature). It is important to minimize the cooling time so that pitched yeast has the best chance of taking over any other micro-organisms.
2.- Most folks recommend that you experiment with ice/chilled water to get the temp you want when adding the boiled wort to the fermentor (consensus seems to be 1 gallon of ice topping off to 5 gallons with chilled water added, but this does not allays work for me, tending to be too hot and forcing me to cool further with an ice-bath while I hope that bacteria is not growing )
So I thought about it. The volume of boiled wort that goes into the fermentor can vary depending on how much initial water you use (2-3 gallons), how strong the rolling boil was and the altitude at which you brew (evaporation loss), and the temperature of the ice and chilled/tap water based on the fridge/city. Makes sense that the that I have trouble getting to 72.5F by guessing the amount of ice each time !
So, I put my scientist hat on. To first order (treating the mixture as water, witch it is with 95% accuracy), the final temperature (Tf) of the 5 gal wort is,
Tf = Tx*(x/5) + Tw*(w/5) + (0.6*Ti - 80)*(i/5)
Where the temperatures are in C and,
Tf is the final wort mixture temprature. Ale yeast wants it to be ~22.5C = 72.5F.
Tx is the temperature of the wort when dumped into the fermentor (typically very close to 100C = 212F).
Tw is the temperature of the water used to top off the fermentor (~15C for tap water and ~3C for chilled water)
Ti is temperature of the ice (typically ~-19C = -2F)
x is the volume of boiled wort in gallons (typically 2-3 gallons)
w is the volume of top-off water in gallons (typically ~1 gallon)
i is the volume of ice measured before freezing when it was water (typically ~1 gallon)
A few comments about the formula,
1.- I derived this formula, so it may contain an error (beware!). Would be nice if someone could verify it. It seems to work for me.
2.- The boiling wort and top-off water terms are simply a weighted average. The ice term also looks like a weighted average but is a bit more complex; the 0.6 factor is due to the fact that it is easier to heat-up ice compared to water, and the -80 term comes from the energy needed to melt ice into water once it reaches 0C=32F.
Ok, so can this formula be useful? You bet! There are two techniques I've found so far,
Super Express cooling - Put a gallon of ice at the bottom of the fermentor, add the boiling wort on top, measure the volume of the fermentor after that and subtract 1 to get the volume of boiling wort (or simply have a graduated boiling pot), then use the formula to calculate how much more ice you need before adding the top-off water (you'll need a supply of ice cubes with known volumes).
Express cooling - Have a fixed about of ice (e.g. 1 gallons). After boiling is done measure the boiled wort volume (related to the height of boiled wort in the pot). Wait for the boiled wort to cool down and reach the Tx that will produce Tf = 22.5C, pour it over the ice and top off. This works well because (1) the boiled wort is far from room temperature and it cools down very quickly, and (2) bacteria won't find it comfortable to live in the cooling boiled wort. This is my preferred method as you don't need to have a bunch of ice-cubes ready and you can increase the amount of ice so you wait less by making Tx closer to 100C (beware, that you can overshoot and get over 100C for Tx, this means that the volume of boiled wart is too low for how much ice you have; don't panic you can add more water to the wort to change x and heat up the fuller boiling put until you get to the new Tx needed).
Anyhow, if anyone is interested I can publish practical tables or maybe write an app so folks don't have to calculate (not doing that at this point since no one may be interested ).
I've been reading this forum and it has helped me brew some nice beers and troubleshoot several issues, so thanks to all!
There is one subject that I think I can contribute to; cooling wort.
This is the info I've gathered so far on cooling wort;
1.- Luke-warm wort is at the highest risk of bacterial contamination (think of leaving a potato salad at room temperature). It is important to minimize the cooling time so that pitched yeast has the best chance of taking over any other micro-organisms.
2.- Most folks recommend that you experiment with ice/chilled water to get the temp you want when adding the boiled wort to the fermentor (consensus seems to be 1 gallon of ice topping off to 5 gallons with chilled water added, but this does not allays work for me, tending to be too hot and forcing me to cool further with an ice-bath while I hope that bacteria is not growing )
So I thought about it. The volume of boiled wort that goes into the fermentor can vary depending on how much initial water you use (2-3 gallons), how strong the rolling boil was and the altitude at which you brew (evaporation loss), and the temperature of the ice and chilled/tap water based on the fridge/city. Makes sense that the that I have trouble getting to 72.5F by guessing the amount of ice each time !
So, I put my scientist hat on. To first order (treating the mixture as water, witch it is with 95% accuracy), the final temperature (Tf) of the 5 gal wort is,
Tf = Tx*(x/5) + Tw*(w/5) + (0.6*Ti - 80)*(i/5)
Where the temperatures are in C and,
Tf is the final wort mixture temprature. Ale yeast wants it to be ~22.5C = 72.5F.
Tx is the temperature of the wort when dumped into the fermentor (typically very close to 100C = 212F).
Tw is the temperature of the water used to top off the fermentor (~15C for tap water and ~3C for chilled water)
Ti is temperature of the ice (typically ~-19C = -2F)
x is the volume of boiled wort in gallons (typically 2-3 gallons)
w is the volume of top-off water in gallons (typically ~1 gallon)
i is the volume of ice measured before freezing when it was water (typically ~1 gallon)
A few comments about the formula,
1.- I derived this formula, so it may contain an error (beware!). Would be nice if someone could verify it. It seems to work for me.
2.- The boiling wort and top-off water terms are simply a weighted average. The ice term also looks like a weighted average but is a bit more complex; the 0.6 factor is due to the fact that it is easier to heat-up ice compared to water, and the -80 term comes from the energy needed to melt ice into water once it reaches 0C=32F.
Ok, so can this formula be useful? You bet! There are two techniques I've found so far,
Super Express cooling - Put a gallon of ice at the bottom of the fermentor, add the boiling wort on top, measure the volume of the fermentor after that and subtract 1 to get the volume of boiling wort (or simply have a graduated boiling pot), then use the formula to calculate how much more ice you need before adding the top-off water (you'll need a supply of ice cubes with known volumes).
Express cooling - Have a fixed about of ice (e.g. 1 gallons). After boiling is done measure the boiled wort volume (related to the height of boiled wort in the pot). Wait for the boiled wort to cool down and reach the Tx that will produce Tf = 22.5C, pour it over the ice and top off. This works well because (1) the boiled wort is far from room temperature and it cools down very quickly, and (2) bacteria won't find it comfortable to live in the cooling boiled wort. This is my preferred method as you don't need to have a bunch of ice-cubes ready and you can increase the amount of ice so you wait less by making Tx closer to 100C (beware, that you can overshoot and get over 100C for Tx, this means that the volume of boiled wart is too low for how much ice you have; don't panic you can add more water to the wort to change x and heat up the fuller boiling put until you get to the new Tx needed).
Anyhow, if anyone is interested I can publish practical tables or maybe write an app so folks don't have to calculate (not doing that at this point since no one may be interested ).