PH question

[Groundtop]

My pH is a little high and in my nute solution and I want to try and lower it naturally. I have read that it is ok to add a bit of citric acid to the mix or white vinegar to lower your solution, and baking soda to raise it. I understand that these organic ingredients don't have any sort of pH buffer, and stand a chance of the solution to revert back to it's old pH, but what if the actual nute solution did contain a pH buffer to maintain the level? I am using maxigrow by general hydroponics which does indeed contain a buffer. Does anyone know if it will maintain the level? Or if there will be any negative effects adding very small amounts of natural acids. Thanks in advance.

 

[TorturedSoul]

I never quite understood the concept of pH buffers as used by people who are speaking of things like nutrient solutions.

<SCRATCHES HEAD> Or maybe it's them, IDK.

Consider:

pH and Buffers Defined
pH is a measure of the concentration of H+ [H3O+] ions in a solution. Only the concentration of H+ and OH- molecules determine the pH. When the concentration of H+ and OH- ions are equal, the solution is said to be neutral. If there are more H+ than OH- molecules the solution is acidic, and if there are more OH- than H+ molecules, the solution is basic.

Buffers
To be able to add a strong acid or base to a solution without causing a large change in the pH, we need to create a buffer solution. A buffer solution contains both a weak acid (HA) and its conjugate base (A-).

Okay, so there are "things" in there that help stabilize a solution's pH...

However, when we mix up any given ratio (and/or strength) of nutrient solution, it does not always land at our target pH. So we'll add either an acid or a base (aka "pH Down" or "pH Up") to that solution. What happens when we do? The pH changes. Why? Because we've "broken the buffers," lol.

I've seen it myself. Mix a solution and, if the pH is off target, add a pH adjuster product. If the solution is buffered, the initial application of the pH adjuster produces very little change. If the pH is still off by at least as much as the amount of change that we were able to cause - and if we're not really thinking, IMHO - then we might then add the same amount of pH-adjuster, assuming that this will cause the same drop (or rise) as before...

...and, "Oh <BLEEP>, the pH just shot past my target!" That's why some newbies end up adding both a pH down AND a pH up (or vice versa) product before it's over with. Which is definitely a non-optimal thing to do.

A well-buffered solution is one in which it is difficult to cause a significant pH change. Attempting to... uses up those buffers. And once that state is reached, additions of an acid or a base will cause much more significant changes.

This is called "breaking the buffer." And that's a pretty apt phrase.

It's a bit more complicated than that, but. A little light chemistry reading might help. Here's a good website (and the one which provided the text I quoted, above):
Buffer Capacity
That article is organized into multiple sections/pages to make it easier to read. The specific section that I linked is titled "Buffer Capacity," but I suggest the entire article be read.

BtW, just about every nutrient manufacturer uses pH buffers to one degree or other. Most just don't place a great deal of emphasis on advertising it. (At the other end of the range, of course, you might find a company that has a marketing budget that's (at least) as large as its R&D budget, lofl, and might have gone to the extreme of naming a product line to reflect its buffers .) General Hydroponics has always been in the former category, not really making a big deal out of such things since they're one of the basic concepts of creating decent nutrients. That may or may not change in the future, now that the company is owned by Scotts Miracle-Gro's "Hawthorne Gardening Company" shell. But, for now at least, it seems to be more or less business as usual. Who knows, lol, maybe it'll end up selling a nutrient line called "pH Proper," paste a bunch of cartoonish labels onto its bottles, and let a former(??? ) marketing guy run the division. IDK.

pH buffers are not like... Hmm. Do you have a membership to a commercial gym, by chance? Or at least ever use a "weight machine" type device instead of free weights when working out? If so, you've seen those stacks of weight plates. And that little pin that the user adjusts to wherever they want in the stack and then it holds everything such that user's choice is maintained? Yeah, pH buffers aren't quite like that, lol.

And this is a different thing than the temporary nature of your chosen pH adjusters in any event. It may appear otherwise, to a degree, for a time. Which is not to say that you won't get lucky and the buffers in your solution won't be "used up" before the usefulness of your adjusters has disappeared. Flip a coin.

Or just do it right and spend what, after all, is (relatively) a very small amount of money on a real pH Down (or pH Up) product . I don't recommend Amazon any more or less than the next company, but it's often useful for spot-checking prices. You are using a General Hydroponics nutrient product, so I checked prices for the GH brand of liquid pH Down. If you're poor, you can get a pint (8-oz.) bottle of the stuff for $8.76 (free shipping). If you're thrifty, you can get an entire gallon (128-oz.) jug for $23.63 (ditto) - which is significantly less than the $140.16 you'd have in 16 pint bottles. And this stuff doesn't expire (or a klutz - don't spill it, contaminate it, or forget to reseal the jug), so unless you're a commercial grower you might only buy one gallon this decade.

All this stuff is really pretty simple, if you think about it. And there's a reason why every question about pH-adjuster products and pH isn't answered with, "Don't bother buying anything other than a bottle of vinegar and a box of baking soda."

 

[Mayne]

I never quite understood the concept of pH buffers as used by people who are speaking of things like nutrient solutions.

<SCRATCHES HEAD> Or maybe it's them, IDK.

Consider:



Okay, so there are "things" in there that help stabilize a solution's pH...

However, when we mix up any given ratio (and/or strength) of nutrient solution, it does not always land at our target pH. So we'll add either an acid or a base (aka "pH Down" or "pH Up") to that solution. What happens when we do? The pH changes. Why? Because we've "broken the buffers," lol.

I've seen it myself. Mix a solution and, if the pH is off target, add a pH adjuster product. If the solution is buffered, the initial application of the pH adjuster produces very little change. If the pH is still off by at least as much as the amount of change that we were able to cause - and if we're not really thinking, IMHO - then we might then add the same amount of pH-adjuster, assuming that this will cause the same drop (or rise) as before...

...and, "Oh <BLEEP>, the pH just shot past my target!" That's why some newbies end up adding both a pH down AND a pH up (or vice versa) product before it's over with. Which is definitely a non-optimal thing to do.

great post, but I do want to say, PH up and PH down together make a good bloom booster. So if you do end up messing up a couple of times to zero in on your figure, dont worry about it, because it is beneficial, especially in flower. I seen this a few times thru my research in the past, and is also in the GrowBoss grow guild.