Superthrive & PH crash

[Izzie]

Originally Posted by RoyalOrchids

Pure water has no pH buffering minerals so even small amounts of a weak acid (or base) can cause a pronounced change in pH. You could use a different water source and ST wouldn't have that big of an effect - but I'm sure you'd rather stick to RO and just keep adjusting it.

Great point- I might have mentioned that I have to do this often in my fish tanks, and it's very easy to over-compensate when playing with pH- which speaks to how easy it can be changed in some cases.

I'm still not taking a side on whether ST is the problem here though. Just don't know enough about it.

[goodgollymissmolly]

Royal you are correct that pH is very sensitive to changes in H+ ion concentration near 7. Anyone who has done a titration knows that. The curve flattens as you move away from the neutral point and additions result in smaller changes because pH is a logarithmic function, not a linear one. You are also correct that "hard" water is buffered to some extent by the hard water ions that tend to keep it basic.

However pH is by definition 1/log [H+]. Therefore adding tiny amounts of H+, as in the case of 2-3 drops per gallon, clearly has a minimal effect because the H+ ion concentration doesn't change much. Even adding 2 drops of a completely ionized acid (known as a strong acid) to a gallon doesn't increase the H+ ion concentration very much. Adding that same amount of acid to a small amount of water obviously has more effect, but to a gallon it isn't that significant and should only result in a small change. I am unaware of what acid is in ST , but I'd be surprised if it's a strong acid. Instead it probably is a "weak" (incompletely ionized) acid that will by it's nature act as a buffer at some pH depending on what acid it is and it's ionization constant. For example you can add vinegar (or it's acid component ,acetic acid) to water til hell freezes over and still not get a very low pH.

The notion that "pure" water pH varies wildly is just an internet rumor. It varies as the log of the H+ ion concentration. As a result of the logarithmic function it does change with minor tweaks in the 7 range. Hard water will act the same way once you reduce it to the 7 range.

[Royal]

My point wasn't that the pH of pure water varies. My point was that water with dissolved minerals (whatever the pH) resists changes in pH more than water without minerals.

Take a gallon RO, and a gallon from the tap. Add the same amount of vinegar to both. The pure water changes more than the buffered water. That's all I was saying.

[Masdyman]

i think i am being misunderstood , i am not too concerned about overdoing it with ST , but the effect it can have when adding it to RO/feed .
I mix 120 lts of ro/feed at a time then adjust the ph , i then only use the ST in smaller quantities when needed in a 2 gal watering can so have never checked the PH at this stage until now .
So if this goes unnoticed and lowers your ph then elements may be locked from your feed .
This is my concern .
The ST instructions say add it to feed but if it effects your feed what is the point ?
If you do a final PH adjustment then no problems should occur ,but what if you don't bother and you use ST on a regular basis ?

[Masdyman]

Originally Posted by RoyalOrchids

My point wasn't that the pH of pure water varies. My point was that water with dissolved minerals (whatever the pH) resists changes in pH more than water without minerals.

Take a gallon RO, and a gallon from the tap. Add the same amount of vinegar to both. The pure water changes more than the buffered water. That's all I was saying.

Royal , you have probably hit the nail on the head , hence my PH drop with RO , i have not tried it with my tap water .
ST has dropped my PH to 4.4 from 7.0 despite some not believing me.
Even if a ph meter was out of calibration i am still getting a 2.6 drop in ph this is a fact .

[CTB]

Can anyone make PH simple and answer beginning questions? See beginnings forum, Thanks

[Ray]

I now see where we are getting the disconnect on the ST pH issue. The RO water has no buffer capacity, so almost ANYTHING you throw into it can shift the pH drastically. I man c'mon, even CO2 from the air forms carbonic acid, dropping the pH a good full point or more. That is not to say that such a pH shift is damaging, however - that all depends on what the ionic species are that are causing the shift. Carbonic acid, for example, is so weak, that the moment you put fertilizer into the solution, the effect of the H2CO3 is negligible.

Unfortunately, as we know very little about the contents of SuperThrive, there is no way to tell what's doing it, so the best advice is to get your fertilizer solution made up and pH stable, and only supplement with that drop or two so it won't have much of an impact.

Back to the K-L-N label for a moment, I am looking at a brand new, 8 oz. bottle (manufactured 2 months ago), and I see instructions for 1) Propagation of cuttings, 2) pretreatment of media (it says "Oasis cubes, sand, rockwool, vermiculite, etc."), 3) Mist propagation, 4) Air rooting, and 5) transplanting and dividing plants. Nothing about regular use or fertilizer supplementation. The website doesn't either. "GoodGolly", maybe yours is an older-, or larger bottle with more room for printing.

Brooke - I cannot argue with your observation, but I was referring to using the hormones at a teaspoon per gallon or more, not 4-6 drops, and I guarantee you'd see flower deformation if used once or twice a week at that rate. After I finished my experiment (fert/fert+ST/fert+my stuff), I intentionally "pushed" the concentration to see what would happen, and that's the result I saw. Fortunately it was reversible by simply backing off.