Grains and pH?

[HopSong]

I know that most/all dark grains tend to lower the pH more than most/all light grains.

The question is... is there a spreadsheet that can help predict the mash pH if I start with strike water at pH 5.5 or other pH?

 

[TrainSafe]

Yes there is. I can't find it on my iPad right now, but search for EZ water calculator

 

[HopSong]

Thanks.. I have that on my computer but couldn't figure how to use it in my case... which is...

I input my water profile for the various salts in my report. But, there is no place to put in the pH of the local water. I also added ONLY the two base grains.. 2-row and Maris Otter.

I was attempting to follow Gordon Strong's recommendation from the podcast he had on BrewSmith. That is... Adjust your water to a pH of 5.5 and mash only the light grains. Add the Crystals and other Dark Grains to the mash at about 5 minutes (or steep them and add to the wort). I added the grains at the end of the mash.

So, in my case.. I made water adjustments to the strike water.. Doing BIAB, I did a No Sparge.. adding all the water at the onset... and also, as above, added the Base Malts.

I'm only interested in what the base grains would do to the water pH.

In my case, doing a 3 g batch, the base grains were 4.6# and 0.52# each respectively.

So, if you can help with this part.. appreciation for any help.

 

[HopSong]

I should probably have opened this in the Science forum....

 

[mabrungard]

Your problem is that you assume that the pH of the strike water is what matters. Water pH does not matter, but the alkalinity of that water does.

 

[gbx]

Read this before you start messing around with your water https://www.homebrewtalk.com/f128/brewing-water-chemistry-primer-198460/

 

[ajdelange]

Water pH does matter and a good spreadsheet requires it to give an accurate mash pH prediction. The effect of water pH is not so profound, however, in the nominal range. Assume water with an alkalinity of 100 mashed at 1.5 qts/lb of a mixture of base malt, caramel and a little black malt. The following pH's can be expected as a function of water pH

Water_pH Water_alkalinity Mash_pH
6 100 5.378
7 100 5.400
8 100 5.403

Needless to say you won't be measuring pH to 3 decimal places with ±0.02 buffers. I've given 3 in the table so you can see the theoretical variation in mash pH as a function of water pH. It isn't much unless your water pH is below 7. OTOH if the alkalinity changes as in

7 50 5.343
7 100 5.400
7 150 5.461

you can see that the pH change is more sensitive with respect to alkalinity than with respect to water pH. However when the alkalinity is modest, below 100 say, then the alkalinity of the base malt dominates water alkalinity and the mash pH is not that sensitive to water alkalinity either.

I'm not sure that any of the spreadsheets or calculators use water pH completely correctly in this regard. However, if you acidify your water to mash pH (e.g. 5.5) then the proton deficit for the water is 0 (i.e. its effective alkalinity is 0). Again, I'm not sure if any of the common spreadsheets or calculators model this properly but I don't think you would be too far off with any of them if you entered 0 in the alkalinity field in this case. Note that if you do this you must change malt or acid or base quantities until the spreadsheet calculates the pH to which you preset the water. IOW if you acidify to 5.5, enter 0 for alkalinity and the spreadsheet shows that you will have a mash pH of 5.4 you would then have to remove a colored malt or add alkali until it tells you 5.5 in order to insure (subject to potentially substantial errors in the malt models as compared to your actual malts) that 5.5 is a valid answer.

 

[HopSong]

This is all for an Oatmeal Stout

My tap water pH is 7.1; Alkalinity from tap is 138; Bicarb is 171 (I boiled the water for 20 min, covered and let cool overnight and siphoned all but the bottom 2" into my kettle); Hardness is 154;

I only added the 2 row, maris otter and instant oatmeal..

Unfortunately, I didn't take a pH reading of the wort at partway thru the mashing before I adde all the crystal and dark malts.

That's why I was wondering if the grains raised or dropped the mash out of the 5.4/5.5 range.. (I pretreated the strike water to 5.5pH)

 

[ajdelange]

By boiling the water (you don't need 20 min) you can, since hardness (assuming it all to be calcium hardness) is greater than the alkalinity, theoretically get the alkalinity down to 50 ppm as CaCO3. If you then neutralize that by adding acid until mash pH is reached you will have water with 0 effective alkalinity. Mashing in with that will result in mash pH set by the MO, 2 row and oatmeal and will prob ably be higher than desired. Additional acid would be required to overcome the alkalinities of those malts in order to acheive a desired mash pH. If you add that extra acid and then add more acid malts at the conclusion of the mash the wort pH will be quite possibly be lower than desired. If you don't add that extra acid then the wort pH will still drop but not to the same level. Wort pH might be where you want it to be but mash pH would have been higher so you wouldn't get the benefits of proper mash pH this way. This is the paradox of GS's method. I have never tried this method in the belief that if you properly handle your dark grains you will not get the harsh burnt qualities that the witholding method purports to avoid.

 

[HopSong]

Thanks AJ.. that helped quite a bit. I will probably go back to my old way of doing things For this brew I was hoping to avoid the initial harsh flavors (which very much mellow with a bit of time)