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Old 01-06-2012, 01:25 PM   #1
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Default Gypsum NOT dissolved !

Hi there !

I'm trying to reduce the pH of my water which is 7.3 by adding Gypsum .

Its solubility is 2 g/l at 20C .

I just added 0.3 grams of it to 1.2 liters of water at 21C , but I can see the salt precipitating and not dissolving completely !

I also added 0.5 grams of CaCl2 .

Now , the pH is 6.7 .

Can I accept this pH , as not all of the gypsum is dissolved ?

Hector


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Old 01-06-2012, 02:05 PM   #2
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Hi there !

I'm trying to reduce the pH of my water which is 7.3 by adding Gypsum .

Its solubility is 2 g/l at 20C .

I just added 0.3 grams of it to 1.2 liters of water at 21C , but I can see the salt precipitating and not dissolving completely !

I also added 0.5 grams of CaCl2 .

Now , the pH is 6.7 .

Can I accept this pH , as not all of the gypsum is dissolved ?

Hector
The pH of the starting water doesn't matter- it's the mash pH that matters.

But still, the CaS04 should dissolve. I add it warmer water, though, as I'm mashing in shortly when I add it. I've never had a problem with it dissolving in water that is 78C.


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Old 01-06-2012, 02:11 PM   #3
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To begin with the pH of your water has little importance in brewing. Second, adding gyspum and calcium chloride will not, theoretically, change the pH of your water. Both are the salts of a strong base (calcium hydroxide) and strong acids (sulfuric, hydrochloric). But as what you buy from the HBS is not pure (calcium chloride often, for example, contains a fair amount of calcium hydroxide) pH can change when these salts are added - especially the chloride.

One of the reasons for adding these salts is so that there will be calcium to react with malt phosphate in the mash tun. That has the desirable effect of lowering mash pH. The other reason is for the flavor active effects of the sulfate and chloride ions.

Gypsum is not, as you have noted, terribly soluble in water. It can take a lot of stirring to get it completely dissolved. It is more soluble in cold water than hot so don't try heating the water to get it to dissolve.
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Old 01-06-2012, 02:41 PM   #4
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One of the many uses of old White Labs yeast tubes is mixing in your salts, a little bit of water and shaking. Always dissolves that way for me.
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Old 01-06-2012, 02:44 PM   #5
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One of the many uses of old White Labs yeast tubes is mixing in your salts, a little bit of water and shaking. Always dissolves that way for me.
That's a great idea! Thanks for that tip. I stir well, and the salts do dissolve just fine but I love the idea of mixing them up in the vial first, and then adding them to be sure.
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Old 01-06-2012, 02:47 PM   #6
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Gypsum is not, as you have noted, terribly soluble in water. It can take a lot of stirring to get it completely dissolved. It is more soluble in cold water than hot so don't try heating the water to get it to dissolve.
i've heard AJ say this before, so I've started adding salts to the cold strike water as its heating. usually by the time it's at temp everything is dissolved, but it generally takes the entire time with a bit of stirring.
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Old 01-06-2012, 02:57 PM   #7
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I just dump mine right on top of the mash as i'm doughing in, never a problem. As in I always hit my target ph, so it must be dissolving.


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Old 01-06-2012, 02:57 PM   #8
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To begin with the pH of your water has little importance in brewing......
In fact , I'm making a mini mash for the first time and I'm going to test my 2-row pale malt to find out my efficiency . I'm going to reduce the water pH to 6.0 by adding salts and also a little acid and then let the mash work . I'll check the pH during the mash , too .

I'm doing this according to John Palmer's "How to Brew" . I mean , reducing the pH by adding salts . Besides , the ppm of the Ca ion in my water is under the desired range ( 16.5 ppm ) , therefore I'm bringing it up to 98 ppm . But , it didn't dissolve completely . That means I have less than 98 ppm of Ca now , or it will be O.K. at mash temperature ?!

All of the salts which I use for brewing are Food-Grade and product of a famous German Chemical Company .

Assay. of my salts :

(CaSO4.2H2O) --> 98 - 102 %

(CaCl2.2H2O) --> 99 - 103 %

Their solubility are also printed on the container :

CaSO4 --> 2 g/l at 20C

CaCl2 --> 1000 g/l at 20C

Should I do my test and see the results , anyway ?!

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Old 01-06-2012, 02:58 PM   #9
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One of the many uses of old White Labs yeast tubes is mixing in your salts, a little bit of water and shaking. Always dissolves that way for me.
You're probably not using much gypsum. Two grams of calcium chloride will easily dissolve in 50 mL of water but 2 grams of gypsum won't. Even so, getting the particles suspended in a small volume of water should make it easier to get it dissolved in the larger volume of the HLT.

I've noted here before that I find it very handy to add the salts to a volume that is an easy multiple of the height of my HLT (1 in my case - I dissolve my salts in 35 mL of water beacause the HLT is filled to 35"). If I need to top off the HLT during the brewing session (and I do) I add 1 cc of the concentrated solution for each inch of water I add to the HLT.
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Old 01-06-2012, 03:40 PM   #10
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Originally Posted by hector View Post
In fact , I'm making a mini mash for the first time and I'm going to test my 2-row pale malt to find out my efficiency . I'm going to reduce the water pH to 6.0 by adding salts and also a little acid and then let the mash work . I'll check the pH during the mash , too .
Making a mini mash is a very good way to establish mash pH and there is some control available via the addition of calcium salts. These react with the phosphate in the malt. The water is only a solvent. You will not be able to reduce the pH of the water to 6 by adding salts unless they contain impurities. The proper approach is to use reasonable amounts of salts to the water and then make the test mash. Or, you could mash in with distilled water and then add the salts to the mash bit by bit checking the pH as you go. This would allow you to work up to the proper amounts of salts gradually but would require careful and thorough mixing and a wait for complete reaction.

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I'm doing this according to John Palmer's "How to Brew" . I mean , reducing the pH by adding salts .
Just so we are perfectly clear on this: it is the pH of the mash, not the water, that needs to be adjusted. Water pH has little effect on mash pH. What is important in the water is it's alkalinity.

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Besides , the ppm of the Ca ion in my water is under the desired range ( 16.5 ppm ) , therefore I'm bringing it up to 98 ppm . But , it didn't dissolve completely . That means I have less than 98 ppm of Ca now , or it will be O.K. at mash temperature ?!
That approach is fine but it needs to be dissolved and you can get it to dissolve as long as you have less than 2 grams per liter though obviously it will dissolve much faster if you have appreciably less than 2 grams per liter. Your proposed 0.3 gram/1.2 liter will dissolve but you will need to stir it until it does. This may take some time.

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Originally Posted by hector View Post
Should I do my test and see the results , anyway ?!
Never hurts to do a test. You will, if nothing else, get some practice with the use of the pH meter.

And no, I didn't see #8 until after I had posted #9.


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