Originally Posted by monkeyman1000
1) The Buffering Capacity graphs created by deLange- The two graphs show the buffering capacity from -20 to -100 mEq/pHkg and -25 to -150 mEq/pHkg. Is the buffering capacity more at -100 and -150 or on the other end of -25 and -20.
The magnitudes of the numbers are the buffering capacities. Thus if the number from the graph is the -100 mEq/kg-pH that means it takes 100 mEq to move the pH of a mash containing 1 kg of the malt 1 pH unit. The reason for the minus sign is that adding protons (acid) results in a decrease in pH. Or put another way the curves in Fig. 20 represent the slopes of the curves in Fig. 19 which are all decreasing with increasing pH for all values of pH.
2) Palmer gives some great examples to work thru in chapter 7. Earlier in the book he introduces the concept of Z Alk and Z RA but from what I can tell in the examples, Kolbach's RA is used. When we are figuring out our own water would it be better to use the Z Alk and Z RA?
On p170 he uses the 'conventional' RA to work an example in which he wants to raise the 'conventional' RA to 150 and starting on p171 he raises the zRA to 150 and gets different answers. This isn't unsurprising as RA is defined as RA = alk - (Ca/3.5 - Mg/7). There are 3 possible values of RA here
RA(4.3) = alk(4.3) - (Ca/3.5 - Mg/7)
RA(4.5) = alk(4.3) - (Ca/3.5 - Mg/7)
RA(pHz) = alk(5.4) - (Ca/3.5 - Mg/7)
where pHz = 5.4, the desired mash alkalinity. 4.3 is the value which makes the alkalinity the M or total alkalinity and 4.5 the pH for the ISO method of alkalinity specification. In the two examples he gives (without specifying end point, i.e. 4.3 or 4.5, for the first) he shoots for the same RA value, 150. Assuming that some level of RA is desired the target for RA(pHz) should be adjusted down as RA referenced to a higher pH (5.4 > 4.5) will be smaller than the RA referenced to a lower pH. I tried to get John away from such heavy reliance on RA but he is still of the opinion that it is the key to all this and it is his book.
As I don't think there is much basis for an RA of 140 or 150 or 160 for this particular beer I don't think it matters much which of the two RA's you use. If you know something about the malts then you won't be calculating RA anyway but will be approaching the problem via the proton deficit method (which is hinted at in the book but not fully developed because there wasn't time). Using the proton deficit method you would calculate the proton deficit of the water with respect to it's pH and pHz. This is obtained from Ct = 1.94 (which he calculates on p172) multiplied by the number of protons required to lower the pH of 1 mmol of Ct from 9 to pHz. From the graph on p127 this is -.1 - -1.04 = 0.94. This results in a proton deficit of 0.94*1.94 = 1.82 mEq/L. To determine how much alkalinity is necessary you would have to multiply by the total amount of water to determine the water's deficit and add to that the deficit of each base malt and light colored specialty malt and subtract the surfeits of any highly colored malts. If the sum of all these is a negative number (a proton surfeit) then you would have to add that much base to absorb those extra protons thus bringing you to pHz. I think the main flaw here is trying to push you to a particular RA when in fact you need to be considering the effects of the malts. There may be a correlation between beer color and malt spec but it is a loose one.
Originally Posted by monkeyman1000
3) With regards to checking mash pH deLange shows that time is definitely a factor. When should the mash pH be checked ( 30 minutes after adding the grains for example) and is their enough time to make an adjustment at that point? Or do you make changes to the next time you brew the same recipe and try to dial it in over successive attempts?
Initially take as many measurements as you can and write them down with the times you took them. Plot these out. It won't take you long to be able to 'lead' your pH meter readings by which I mean have a pretty good idea as to where they are going to level out before they actually do.
Most of the change should have taken place in the first 20 minutes or so. I'd say that unless things are drastically off you should defer adjustment until the next brew. Making a test mash with a portion of your grist (well mixed) and some of the water you intend to mash with should prevent things being drastically off.