Pre sparge gravity

Hi!

Is there any way BeerSmith can tell me my pre-sparge gravity. I would like to check if my mash went well before I start pouring in all of the sparge water. That way I can still decide to hold back or not.

Thx!!

Doing an iodine test will tell you if conversion is complete. If it is, there's nothing to gain from extending the rest time.

This would be a real swag at the number.  Basically, the program would need to assume that you have 100% conversion and then give you the saturated wort gravity related to your water to grist ratio for your mash.  Without any other information on the conversion efficiency of your system, it could do no better.  Kai Troister had a good presentation on efficiencies which covers this and can be found at http://braukaiser.com/wiki/index.php/Understanding_Efficiency.

In essence, the number BeerSmith gave you would be a pure speculation. 

My question is why would you hold back water?  Generally when I brew, my main target is the volume.  If I am off by a couple of points, I can decide to let it ride, dilute the wort down a little, add some DME to bring the gravity in line with expectations, or adjust my boil time to compensate for the difference (this is my preferred option the few times this has happened).  In expectation of the possibility of adjustment, I will target a 90 minute boil with my first hop addition at 60 minutes.  This gives me plenty of opportunity to lengthen or shorten the boil times according to any adjustment in gravity I need to make.  Since I know my boil off rate, I can calculate the difference needed to bring the wort into alignment with where it should be from the beginning and then start the timer.  My process allows for a 9% loss when pouring into the fermenter, so I have that value to work with in volume and still hit my targets all around.

Oginme said:

This would be a real swag at the number.  Basically, the program would need to assume that you have 100% conversion and then give you the saturated wort gravity related to your water to grist ratio for your mash.  Without any other information on the conversion efficiency of your system, it could do no better.  Kai Troister had a good presentation on efficiencies which covers this and can be found at http://braukaiser.com/wiki/index.php/Understanding_Efficiency.

In essence, the number BeerSmith gave you would be a pure speculation. 

My question is why would you hold back water?  Generally when I brew, my main target is the volume.  If I am off by a couple of points, I can decide to let it ride, dilute the wort down a little, add some DME to bring the gravity in line with expectations, or adjust my boil time to compensate for the difference (this is my preferred option the few times this has happened).  In expectation of the possibility of adjustment, I will target a 90 minute boil with my first hop addition at 60 minutes.  This gives me plenty of opportunity to lengthen or shorten the boil times according to any adjustment in gravity I need to make.  Since I know my boil off rate, I can calculate the difference needed to bring the wort into alignment with where it should be from the beginning and then start the timer.  My process allows for a 9% loss when pouring into the fermenter, so I have that value to work with in volume and still hit my targets all around.

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Very interesting.

I though I could measure expected gravity after the mash (based on my conversion percentages) and then decide if I want to pour more or less sparge water.

Using the boil time before a hop addition (as you mention boil 90 mins but dont add hops till 60 or 70 mins) is also a solution. But it seems like a less elegant one as I am wasting time and energy boiling off water I didnt need to add in the first place.

A friend created an excel sheet that calculates expected gravity after mash and I just thought maybe BeerSmith also has such calculations included.

This is probably a very silly question. Assuming 1.050 gravity at 10L, do I have 1.055 gravity if I boil off 1 liter?

The concentration of sugars during boil is very predictable and easy to calculate.  During the boil, the only thing that is lost is volume, so the amount of sugar remains constant.  You can track the affect of boiling off a bit of wort by using this balance of sugars before and after as such:

Sugar points is the gravity of the wort minus 1 and times 1000.  Thus, 1.050 is (1.050 - 1) * 100 = 50 sugar points. 

The amount of sugar in the wort can be estimated as 50 sugar points * 10 liters of wort = 500 points.

If you boil off 1 liter, the resulting wort is now 9 liters.  You have the same amount of sugar in the kettle, so the gravity then becomes 500 points / 9 liters = 55.5 sugar points.  This translates to a 1.055 to 1.056 gravity reading.

In terms of the expected gravity after mash, you can create a spreadsheet based upon the data from Kai's site which represents the expected gravity at 100% conversion.  Your difference from that really measures your conversion rate during the mash.  Changing the amount of sparge water is then really no different from changing the boil off through adjustment of the boil time.  Keeping the water volumes consistent and making a slight variation on boil time works if you have enough buffer in your calculations at the end of the boil to still get your fermenter volume.  Likewise, changing the amount of water you sparge with leads to the same issue at the end of the boil.  Since my boil off rate is very predictable (and I do full volume BIAB for most of my brews), it is much easier to change the time and nail the gravity on the nose than to assume an extraction rate for the sparge and try to guess volume that way.