### Author Topic: Gypsum post fermentation  (Read 1027 times)

#### morticaixavier

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##### Gypsum post fermentation
« on: December 03, 2013, 01:22:19 PM »
Anyone want to help me with some math?

If I want to experiment with post fermentation gypsum additions and I only have a scale that reads 1 gram or more (no decimals) I will need to dilute a much larger amount of gypsum with something else so that I can realistically measure a given amount into my pint glass (or 1 pint mason jar, or whatever).

So I will boil and chill say 100 ml of filtered or RO water (RO probably better) and add ?? grams of gypsum. I will then add ?? ml of the resulting liquid to my 2 fluid oz of beer and taste. When I achieve the desired flavor profile I will multiply the ?? grams of gypsum represented by the ?? ml of solution by 320 to get the amount to add to the keg.

so:
gypsum5 gallons = 320 * ((gypsum100 ml/100ml)*solution2 floz)

simplify:
X = 320 * ((Y/100)*Z)
Where X is the total amount of gypsum for 5 gallons of beer, Y is the grams of gypsum added to the 100 ml of water, and Z is the ml of solution added to the sample 2 floz to achieve the flavor profile I want.

Is this right?

what would be a good place to start in terms of how many grams to dissolve in the initial 100 ml of water?
"Creativity is the residue of wasted time"
-A Einstein

"errors are [...] the portals of discovery"
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#### denny

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##### Re: Gypsum post fermentation
« Reply #1 on: December 03, 2013, 01:40:38 PM »
This info from Beer and Wine Journal IPA Experiment may be helpful...http://beerandwinejournal.com/ipa-experiment/

"Measuring the tiny amounts of gypsum required could be a problem. One way around this would be to make a known gypsum solution and add this. However, the solubility of gypsum is around 2.4 g/L in pure water. As such, you’d need add a total of just less than 2.0 qts. (2.0 L) of this solution to the beer by the end of bottling. So, when adding gypsum, just do your best to measure out the small amount. Then, wet it into a slurry. This will still likely raise some foam (and lower your level of dissolved CO2) when you stir it in, but it won’t dilute the beer as much. Incidentally, the solubility of calcium sulfate increases in colder water, contrary to how most solids behave, so don’t try to use hot water to make the slurry. The solubility of gypsum is increased in acidic solutions, so it’s possible that you could make an acidified known solution of gypsum, but then you’d also be dosing the beer with whatever acid you used."
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#### kramerog

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• Posts: 1604
##### Re: Gypsum post fermentation
« Reply #2 on: December 03, 2013, 01:50:27 PM »
The math looks fine assuming you are not adding a lot of gypsum solution to your 2 oz of beer.  If you add 6 ml of solution to your 2 oz (~60 ml) sample, the equation will be off by ~10%.
« Last Edit: December 03, 2013, 02:09:42 PM by kramerog »

#### morticaixavier

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##### Re: Gypsum post fermentation
« Reply #3 on: December 03, 2013, 01:57:59 PM »
so if I add 2.4 grams of gypsum (call it 3 for reasons stated above) to 1 liter of boiled chilled distilled water I will have saturated the solution.

Instead I can add 1 gram to 400 ml of water and achieve the same saturation level. so each 1 ml of solution = .0025 grams of gysum.

So:
X = 320 * ((.0025)*Z)

cool. now I decide on the value of Z based on sensory trials and solve for X.

Thanks, I knew I was close but I wanted to a double check. I'm guessing the volumetric addition of 1 gram of gypsum in 40 ml water will be negligible but I suppose if it isn't that will be obvious and will just change the .0025 number slightly.

I just realized I can use beer instead of water to make the solution and it will probably help dissolve the gypsum better than water would and would have no flavor impact on the sample.
« Last Edit: December 03, 2013, 01:59:42 PM by morticaixavier »
"Creativity is the residue of wasted time"
-A Einstein

"errors are [...] the portals of discovery"
- J Joyce

#### kramerog

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• Posts: 1604
##### Re: Gypsum post fermentation
« Reply #4 on: December 03, 2013, 02:06:32 PM »
I think you'll want your standard solution to be 1 L or bigger so you can accurately and precisely measure the gypsum on your scale.  Lets say you want your 2 oz to have 50 ppm of gypsum by adding 1 ml of solution.  To have 50 ppm in 2 oz you would have to add ~3 mg of gypsum to your sample and ~0.3 g of gypsum to your 100 ml of standard solution. Your scale can't measure anything precisely (2 sig figs) until you get to 10 g.  So in my scenario you would need to make a 4 L solution containing 12 g of gypsum.
« Last Edit: December 03, 2013, 02:15:12 PM by kramerog »

#### morticaixavier

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##### Re: Gypsum post fermentation
« Reply #5 on: December 03, 2013, 03:18:17 PM »
I think you'll want your standard solution to be 1 L or bigger so you can accurately and precisely measure the gypsum on your scale.  Lets say you want your 2 oz to have 50 ppm of gypsum by adding 1 ml of solution.  To have 50 ppm in 2 oz you would have to add ~3 mg of gypsum to your sample and ~0.3 g of gypsum to your 100 ml of standard solution. Your scale can't measure anything precisely (2 sig figs) until you get to 10 g.  So in my scenario you would need to make a 4 L solution containing 12 g of gypsum.

True, I would have to add at least 10 grams to get a really precise result. However, as in handgrenades, horseshoes, and thermo-nuclear warfare, close might well be enough in this case. I suppose, if I knew the actual saturation point of gypsum in beer I could just keep adding it till it won't dissolve anymore. and then I would know the sulfate content. how theoretical!

So if 3 mg of gypsum would add 50 ppm of sulfate to 2 floz and 1 ml of saturated solution contains 2.5 mg I will need 4 ml to achieve close to 200 ppm and 6 ml to achieve 300 ppm. that's more than a tablespoon of solution. hmm. I'll want to use beer for sure.
"Creativity is the residue of wasted time"
-A Einstein

"errors are [...] the portals of discovery"
- J Joyce

#### kramerog

• Senior Brewmaster
• Posts: 1604
##### Re: Gypsum post fermentation
« Reply #6 on: December 03, 2013, 04:07:03 PM »
Check to see if your scale is accurate at low weights by weighing one and two nickels.  They should weigh 5 and 10 g.