Adjusting Beer pH

I’m interested in playing around with pH in finished / packaged beers and seeing how it affects flavor presentation. Occasionally I have beers that finish as high as 4.7 / 4.8, and when that happens, I’d like to lower them to see if I’m missing a potentially better beer.

Problem is, I’m not really confident about how to go about it. I followed Sir Gordon Strong’s advice from Brewing Better Beer, but was amazed at the beer’s (American IPA) ability to buffer pH reduction using phosphoric acid at 10%. I think I used almost 20mL in a 5 gallon keg and only saw a reduction of about .1. I stirred it thoroughly, and even let it rest for a few days and then remeasured, but it is definitely possible I overlooked something. Lactic Acid is much stronger at 88%, but I fear the negative effects of using such a flavorful acid.

Does anyone have any experience with this? Success, or failures? Is using as much phosphoric acid as is needed to get a sufficient reduction (below 4.5, at least) fine to do, even if it’s 100mL or something?

II would pH adJust a small sample to see if there’s even potential there before moving on to a full keg

I was going to post this under the heading “Did You Ever Pull One Back From The Brink” but it seems to apply to your post.

Recently I had a request to brew a Honey Brown Lager and right up to the end it was text book.
Periodic taste testing indicated that it had all the makings of a very good beer. But upon the last taste test after lagering for 8 weeks and being fully carbonated it tasted very acidic. I ph tested the beer and it read 4.08 which is low so I decided to add some sodium hydroxide solution to cut the acidity.
After I ran some calculations I ended up adding 1.4 grams of hydroxide which raised the pH of the beer to 4.14 which is far lower than the 4.6 I was shooting for. Even though I undershot the increase in the pH the results were severe. The beer lost 2 shades in color and almost all its flavor. It was like drinking water.
I have to say I was in shock that 1.4 grams of hydroxide could make such a drastic change in 5 gallons of beer. Especially when you consider the size of the additions we use during the brewing process.
Well faced with what could be the greatest of my many public humiliations I decided to blend in a strong malty ale and see if I could rescue it. The blending added back some of the flavor but the results were less than I was hoping for. At this point I felt that I had done enough harm as well as wasting time and money and decided to accept it as it was. I was going to serve it at a party in two weeks and was resigned to watch people wince as they drank it .
I don’t know what happened in the two weeks between the rescue mission and the party but when I tried the beer again just before service it turned into one of the best beers I brewed. The acidity level was what I was shooting for and the flavor was back and better than ever. The brewing gods had been truly merciful.

Although I can’t give you any specific directions as to how to go about adjusting your Ph I Hope this proves insightful.

When you say hydroxide, do you mean calcium hydoxide (slaked lime), sodium hydroxide (lye) or somethin else ?

Probably off topic but I will add it here: I have added things back to beers post-fermentation because I botched something up earlier in the process. I had a spiced pumpkin ale that was too dry (the style is better suited for slightly sweet) so I “back-sweetened” it by boiling some water and adding 3-4 ounces of brown sugar. Added that mixture to the keg and bingo, much better. I once had a beer that lacked ‘crispness’ so I boiled some water and added 1g of gypsum [to back-sulfate the beer] and added that to the keg… bingo, crisper beer and a saved batch. I just had a couple of pale beers where I [stupidly] added too much sulfate to the mash. So I “back-chlorided” the beer with boiling water and 1.2g of CaCl. It worked. Adjusting the pH later seems trickier and I agree with the previous mention of trying it in a smaller amount to see if you can project how much would be needed for 5 gallons. Cheers and good luck.

Pickling Lime.
If I was going to try raising the pH again I would go with Sodium Bicarbonate and see if it gave a more predictable result.