Hmmm, I am going to just give you some round about figures for the 6.5 gallon pre-boil as its good to understand what to adjust when using brunwater and you can use the 8.8 g mash, 6.5 g preboil and 6.5 g sparge as a jumping point for use later as it seems this may be a case of jumping in the cart without a horse or wheels, also I will leave the actual flavor ions balanced in my numbers given because I think your unaware of this aspect of water manipulation yet so it best to let you execute differently as you come to understand it better and will sum up some reflections about this below too. But I think some other investigating about boil quantities and volume adjustments are in order first and foremost then you can use the values given to work within the desired parameters found at that time.
I am not going to get into extreme detail as volume/ boiloff etc… is something you have to learn on your own depending on your exact setup. But FWIW if I were to boil only 6.5 g I will lose 1.25 gallon to boil off and cooling and also lose about .75-1.0 gallon to trub and deadspace with lightly hopped beers(eg: 1-3oz). So this means I would end up transferring only 4.25g or so to the fermenter and when transfering to keg it would be 3.5> see where I am going here. Not sure how far down the path you are with the hobby but attending to things like volume etc… may be more in order before you finish planning a full blown partigyle without knowledge of what goes down otherwise your brewday will be hectic to say the least. My statement about liberal water use is the best advice here. Also as shown below you may not even start with 6.5 gallon so give er some reflection so it all comes together primo is all I want to lean on today. If you decide to “wingit” dont say you weren’t warned> :mrgreen:
IE: 8.8g to 18# of grist will equal a full runoff of 6.5gallons without accounting for dead space also which will be anywhere from .25-1.5 gallons depending on equipment parameters. Also if you only add 6.5 gallons of sparge I am not certain if you will see a full runoff of 6.5? Batch spargers could speak to this, I am unsure as I continuous sparge(fly sparge)for all my runnings.
Back to water then:
Now as-is without adjustment your sampled room temp PH of the mash would be 5.7 which is fine as the actual mash PH would be 5.4-5.5 due to the temperature shift. But the mash will not contain any calcium which is beneficial for reasons other than just PH. Also the SO4:Cl ratio vears towards very malty. It is the actual kettle SO4:Cl ratio that matters but as shown in brunwater an addition of just Calcium chloride in the mash would cause too high of Cl without even hitting the proper Ca and you can temper this then by using an addition of both calcium chloride and gypsum to keep the Cl in check and at the same time establish a ratio desired.
Ca: 4.73 mg/ l
Cl: 25 mg/l
SO4: 9.7 mg/l
Mg: 0.8 mg/l
Na: 33.5 mg/l
Alk: 40.5 mg/l
HCO3: 49 mg/l
Mash PH at 5.4( Room temp reading of 5.7PH)
SO4:CL ratio of 0.4 (very malty)
Add 4.4 gram gypsum, 2.6 gram calcium chloride.
Mash PH at 5.2( room temp reading of 5.5PH)
SO4:Cl ratio of 1.3 (balanced)
[color=#FF8000](I would also add 1.3gram of lime actually to raise the PH back towards 5.4(room temp 5.7PH)
and this also brings the Ca content up to 78ppm. But this addition is just semantics and personal choice, any mashing PH of 5.2-5.5 is just fine. In addition my thoughts are a balanced to slightly bitter SO4:CL ratio will be appropriate and balanced right now will give you a baseline for both beers going forward.)[/color]
Also now you are not sparging just using first runnings, so what happens is a majority of the calcium will not make it to the kettle so a small addition of 0.7 grams of gypsum and 1.3 grams of calcium chloride will ensure the kettle is at/around 50ppm calcium. Calcium in the boil does many things also, all around calcium is very beneficial) the other thing is because the calcium chloride adds Cl as spoken to above, you add a touch of gypsum to keep your SO4:CL ratio right around 1.3(balanced)
For the second beer add the following minerals either to the kettle or sparge water of 6.5 gallons to do the same as stated above:
3.3 grams of gypsum and 2.0 grams of calcium chloride.
Then one thing to do to the sparge in addition is add either 9.5ml phosphoric 10% or 1.5ml lactic acid 88% to lower the alkalinity and drop PH of the sparge water to 5.6-5.7 to keep final runnings under 6.0PH