Baffled by Mash Ph

[jasonandmollyb]

I'm a newbie to brewing and  so far have made two successful batches beers in my Brewers Edge.  Everything seems to be going really well, with both the finished product and the with Beersmith, except for one thing.  The calculations for the acid additions seem to be way overshooting the actual need.  Each time I added about half of what Beersmith 3 recommended (2 Tbsp of phosphoric acid) and each time I went from a starting Ph of 7.6 water to around 3.5.  I dumped the water and started over adding only an 1/8 tsp and the water went to around 6.0, making the eventual mash perfect at 5.4. 

I assume I must be doing something wrong, but I can't for the life of me understand why using so little acid (compared to what is recommend is enough to change the value so dramatically.

I've used two different calibrated Ph Meters, tested the water (both before and after the additions) at about 70 degrees each time.  I'm also taking samples from the top and out of the spigot to make sure there isn't a mixing issue. I'm at a complete loss.  Does anyone have any idea where I could be going wrong?  Before anyone points at Beersmith as the culprit, the Bru'n water while slightly different, still have much higher results than what I expected.

[Oginme]

So, let's understand that the acid additions recommended by BeerSmith are to control the pH of the mash and not your water.  For the most part, the pH of your water means very little to the mash pH.  It is more the minerals and ions in your water which will affect the pH of the mash. If you use acid, pay no attention to the water pH once you have added the acid.

Next, the model in BeerSmith is based upon a water calculator developed by Mark Riffe.  Mark has publicly stated that his model overestimates the buffering capacity of the wort and therefor calls for more acid than is necessary -- by about 60%.  There is a sticky in the 'All Grain/Advanced' section where I linked Marks comments concerning the high acid estimations from his calculator as used in BeerSmith.  Other calculators have this problem to a lesser degree, but it becomes especially noticeable when you have a thin mash,such as with BIAB or similar systems.

Hope this helps a bit.

[jasonandmollyb]

It does help a bit, thanks!  I have read not to pay too much attention to the water itself, but when it came up at 3.5 Ph after I added half of the recommended acid, I figured there was no way that it was going to get less acidic, unless I'm just misunderstanding the concept. I've seen countless accounts, videos, etc of people just eyeballing it with a cap or so of acid and it turning out fine.  It seemed odd that with me, only 1/8 of a teaspoon was what ended up dialing everything in.  I guess at the end of the day, I can always tweek as I perfect a recipe.  I'm just one of those people that likes to really understand everything I'm doing. And right now, I just don't.  Yet.

[Oginme]

Water is a pretty finicky beast.  On its own, H2O has no buffering capacity.  It is however an awesome solvent, so most waters carry a lot of minerals and ions.  It is these minerals and ions which give the water its pH and buffering capacity.  I am guessing that you had your water tested, received a report on it, or are using reverse osmosis treated water.

If you had it tested or have a report on the mineral contents, it is predominantly the Bicarbonate concentration which controls the buffering of the water.  It will resist small changes in pH and alter its soluble form shifting the balance of H2CO3 <--> HCO3- <--> CO3-- with the change in pH.  SInce your water pretty quickly acidified with even a little acid seems to indicate that your Bicarbonate level is pretty low or you are using RO water.

When you add the grains to the water, the water also solubilizes many of the minerals from the grains and that brings the pH down also.  Depending upon the amount and types of grains you are using, this could be to the high 5.9's for pH or down to below 5.0 pH for grists with a lot of roasted or high colored caramel/crystal malts.  This is part of the reason there are a few water calculators out there for brewers to use and why there is still a lot of hand-waving about the accuracy of any one of them.