Epsom salt - add after boiling?

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DrGero

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I'm getting deeper into water chemistry, and I wonder way the label on my Epson salt (magnesium sulfate) from Brewferm says: "ADD AFTER BOILING". It's printed with capital letters!

What is the benefit of adding it after boil?

What is the risk of adding it before mash?

Assume that I want to add 2 grams of Epsom salt:
If I add it after boil, the amount of water will be significantly less, let’s say I start with 32 liters of water (mash + sparge), but after boiling I typically have 25 liters. Adding 2 grams of Epsom salt in 25 liters of water will of course give me a different ppm then adding it to the 32 liters. How do I deal with this (if I continue to add it after boiling)? Add 25 / 32 * 2 grams after boiling?
 
I'll stick my neck out and say "add after boiling" refers to boiling the brew liquor to reduce carbonates (if doing such things), not boiling after mash (with hops, etc.).

Like you, I can think of no good reason to add salts to the finished (boiled) wort.
 
The only reason I can think of is to avoid concentration of minerals in the water due to boil off.
My question to you however is why do you want to add epsom salt?
 
strange-steve said:
The only reason I can think of is to avoid concentration of minerals in the water due to boil off.
My question to you however is why do you want to add epsom salt?
Click to expand...

The main goal is to add sulfate, if I used only Gypsum my calcium level might be too high (> 150 ppm). I'm using Gypsum as my primary source for sulfate, but also use Epsom salt if my Calcium level gets too high. I’m not adding more than 30 ppm of Magnesium!
Is there a better way of doing this?
 
That's a good reason, many people think they need to add magnesium to their water but it's really not necessary. Since you're adding it for the sulphate rather than mash acidification then you could add it at any stage of the process, pre or post boil.
 
I don't do anything too sophisticated to treat my water. I just follow Graham Wheeler's simple water treatment method. Which is to boil the required water and for a 23/25 litre batch add 10 g of calcium sulphate once boiling point is reached and to boil for 30 minutes. Then leave it to cool and allow the carbonates to precipitate out. After that add just 1 gram of Epsom salts. The explanation for adding the Epsom salts after the boil is that it would otherwise interfere with the precipitation of the carbonates. Finally rack off the water leaving precipitates behind.
One day I may progress to a more sophisticated approach but for now I find this works for me.
 
oldgreywolf said:
... 23/25 litre batch add 10 g of calcium sulphate once boiling point is reached and to boil for 30 minutes. Then leave it to cool and allow the carbonates to precipitate out. ...
Click to expand...
One of the bazaar things about calcium sulphate (gypsum) is that it will dissolve in cold water much better than hot. So you may well have gypsum among your precipitated carbonates.

Don't ask me to explain why, I've no idea.


(EDIT: Going back to the OP and the "ADD AFTER BOILING" advise, perhaps Epsom Salts (magnesium sulphate) is the same?)
 
oldgreywolf said:
I don't do anything too sophisticated to treat my water. I just follow Graham Wheeler's simple water treatment method. Which is to boil the required water and for a 23/25 litre batch add 10 g of calcium sulphate once boiling point is reached and to boil for 30 minutes. Then leave it to cool and allow the carbonates to precipitate out. After that add just 1 gram of Epsom salts. The explanation for adding the Epsom salts after the boil is that it would otherwise interfere with the precipitation of the carbonates. Finally rack off the water leaving precipitates behind.
One day I may progress to a more sophisticated approach but for now I find this works for me.
Click to expand...

Do you know what is in your water to begin with? If not then you could be wasting your time, because you're unlikely to get the alkalinity below 60ppm using the boiling method. Your water could be below that in the first place, or if not, it's still too high for a pale ale. If you know what the alkalinity is, then a simpler approach is to add acid to lower it. It only takes a few seconds and it's much more effective.

I can't see how the addition of Epsom salt would interfere with the chalk precipitation, if anything I would have thought it would speed it up.
 
peebee said:
One of the bazaar things about calcium sulphate (gypsum) is that it will dissolve in cold water much better than hot. So you may well have gypsum among your precipitated carbonates.

Don't ask me to explain why, I've no idea.


(EDIT: Going back to the OP and the "ADD AFTER BOILING" advise, perhaps Epsom Salts (magnesium sulphate) is the same?)
Click to expand...

After a 30 min boil I would be very surprised if the gypsum hadn't dissolved, that addition is well below the solubility limit even in boiling water.

A quick Google also tells me that the solubility of magnesium sulphate increases with temperature up to 500g/L at 100°C so that isn't it.
 
oldgreywolf said:
I don't do anything too sophisticated to treat my water. I just follow Graham Wheeler's simple water treatment method. Which is to boil the required water and for a 23/25 litre batch add 10 g of calcium sulphate once boiling point is reached and to boil for 30 minutes.
Click to expand...

I'd be surprised if you can get 10g of CaS04 to dissolve in 25l of water once it's reached 100C. According to the chart on Wikipedia you're looking at a solubility of 200mg/kg of pure water at 100C. For 25kg of water that's 25*200 = 5g maximum. If you want 10g to dissolve and be in solution for the 30 minutes then you need to add it while the water's still at room temperature.
 
foxbat said:
I'd be surprised if you can get 10g of CaS04 to dissolve in 25l of water once it's reached 100C. According to the chart on Wikipedia you're looking at a solubility of 200mg/kg of pure water at 100C. For 25kg of water that's 25*200 = 5g maximum. If you want 10g to dissolve and be in solution for the 30 minutes then you need to add it while the water's still at room temperature.
Click to expand...

He doesn't actually say 25L of water, he says the required water for a 25L batch. Also I think the stuff we use is calcium sulphate dihydrate which is a bit more soluble. Even so it's interesting that Bru'n Water says the solubility at 100°C is 1.6g/L which is considerably higher than the chart you linked :hmm:
 
strange-steve said:
Do you know what is in your water to begin with? If not then you could be wasting your time, because you're unlikely to get the alkalinity below 60ppm using the boiling method. Your water could be below that in the first place, or if not, it's still too high for a pale ale. If you know what the alkalinity is, then a simpler approach is to add acid to lower it. It only takes a few seconds and it's much more effective.

I can't see how the addition of Epsom salt would interfere with the chalk precipitation, if anything I would have thought it would speed it up.
Click to expand...

Well I do now as a result of your comments. I've done some research and got my local water report. The mean alkalinity is 300 mgHCO3/l and the calcium 130 mgCa/l, which suggests (I think ) that I have been overdoing it on the calcium addition front?
I've read your article on water treatment, which is first class. One of the few more in depth articles on water treatment that I have been able to understand. I've found water treatment chemistry a bit challenging which is why I followed the simple Graham Wheeler approach. I've decide as a result of all these useful comments to take a more 'intelligent' approach. I like the use of CRS to adjust my water and have devised a simple spreadsheet to help me calibrate the quantities required.
 
peebee said:
One of the bazaar things about calcium sulphate (gypsum) is that it will dissolve in cold water much better than hot. So you may well have gypsum among your precipitated carbonates.

Don't ask me to explain why, I've no idea.


(EDIT: Going back to the OP and the "ADD AFTER BOILING" advise, perhaps Epsom Salts (magnesium sulphate) is the same?)
Click to expand...

I think you are spot on there because I have always had a milkly residue at the bottom of the boiler after this process and I've always thought it must be a good element of the calcium rather than just precipitated carbonates. Although it was a simple process, I am now seeing that it is a bit of a sledge hammer approach.
 
Hi guys
So did We say the Epsom and gypsum were best added to the boil (pre/post) rather than mash?
I'm about to start the mash but was just going to use CRS on it own to treat the whole volume of water

Cheers
 

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