Will the real Gypsum step forward!

[Grok]

In my pursuit of thriftiness, I went in search of an alternate source of Gypsum other than the LHBS, and discovered there seems to be about 3 different basic forms of it with a few sub branches as well.

• CaSO4 Calcium Sulfate (anhydrite) anhydrous state CAS 7778-18-9 MOL 136.14
• CaSO4 2H2O Calcium Sulfate Dihydrate CAS 10101-41-4 MOL 172.17
• CaSO4 1/2 H2O Calcium Sulfate (bassanite) hemihydrate CAS 10034-76-1 MOL 145.15

Products like Plaster Of Paris, garden and agriculture soil dressings, and gypsum hard board building products spring to mind.
LHBS don't seem to list the MSDS for their gypsum products, but some do like KK and they use anhydite version (CAS 7778-18-9), but list both CaSO4 and CaSO4 2H2O, KL only have a MSDS for dextros attached for their gypsum...not much help there!
Scouting around the net, it doesn't seem clear as to what actual type of gypsum is used in the calculators, and to me, people seem to refer to gypsum as if there is only one type.
The different molecular weights (MOL) will affect the actual amount one should add to the brew water.

So my question that I can't seem to find a sturdy answer for is, which form of gypsum do the brew salt calculators use?

 

[Coalminer]

CaSO4 2H2O Calcium Sulfate Dihydrate

 

[MHB]

Coalminer is right, the Dihydrate is by far and away the most common.

Where you and me are going to disagree is on the how stupid it would be to use non food grade anything in our beer!
Industrial and agrocultual chemicals are going to be a lot cheaper than food grade, for very good reasons. Food grade wont have any dangerious contaminants, will be what it says on the label and in the form stated. By that I mean if it says dihydrate it will be all dihydrate not a random mixture of an- and hemi- hydrate... wont have a fair amount of other random stuff in it.
Means when you do your calculations you actually get the right answer.

The easy way to do the calculation is if you know the hydration state. For the Dihdrate its 23% by weight Calcium, For Calcium Chloride its usually Hexadydrate (CaCl2.6H2O) so 18% Calcium. From there its really easy.

I just cant see how adding products from questionable sources in an attempt to save fractions of a dollar in a brew makes any sort of sence. Invest in efficent heating and good insulation does make sense, that will save you money on every brew.
Focusing on making good beer from quality ingredients that is safe and enjoyable to drink, knowing you are saving a motza on tax anyway will do me.
Mark

 

[Coalminer]

Grok, I use an average of about 5-7 grams / brew.
I get it from my LHBS 250g tub $9:95
Thats about 25 cents/brew for the real deal

 

[Grok]

Well, it's not really about the $, that's just an excuse to focus in on a particular subject, but I do enjoy finding alternates sources of all sorts of things, just my curiosity I guess. But what I usually find is that it leads me to a far better understanding of the given subject, the pursuit of knowledge for knowledge sake is a noble cause in my book and is what Universities are or should be about.
I agree one should be careful with agri products and such and definitely do your technical research carefully before using anything in your food.
I wasn't really after a lecture on such, but thanks for the concern MHB.

However, back to my question about the calculators, I am not convinced that the Dihydrate form is the norm, for instance the KK Gypsum product MSDS
https://www.keg-king.com.au/Downloads/SDS-(Calcium_Sulfate).pdf is interesting reading and clearly states CAS number 7778-18-9 which is for the Anhydrous form.
Here is a thread on this subject from Homebrew talk.com that has me thinking about this.
Same gypsum we buy at LHBS?
And another link stating Anhydrous form: Brewing Gypsum: Calcium Sulphate - Arishtam India

 

[Grok]

Looks like no one is offering any comments here about the calculators, so I'll sign off by leaving this snippet of info for those who are interested from Iowa State University site (presumably accurate) about Calcium Sulphate.

"Gypsum is calcium sulfate (CaSO4). Refined gypsum in the anhydrite form (no water) is 29.4 percent calcium (Ca) and 23.5 percent sulfur (S). Usually, gypsum has water associated in the molecular structure (CaSO4·2H2O) (dihyrdate form) and is approximately 23.3 percent Ca and 18.5 percent S (plaster of paris). Gypsum fertilizer usually has other impurities so grades are approximately 22 percent Ca and 17 percent S".

I guess for home brewing purposes the percentage difference between the forms is not a significant factor, but would be on commercial scales, check the SDS (if you can find one!).

 

[theSeekerr]

You would notice if you were purchasing bassanite AKA plaster of paris, because it likes to set into a brick when wetted.

The mostly-anhydrous form, Calcium Sulfate γ-anhydrite, is highly hygroscopic and will slowly spontaneously convert to the dihydrate in the presence of H2O.

The totally-anhydrous form, Calcium Sulfate β-anhydrite, is stable.

"Gypsum" specifically refers to the dihydrate form....all these chemicals are calcium sulfate, but only Calcium Sulfate Dihydrate is "gypsum".