Non-linear changes in PH?

Indoor Growing Hydroponics
61

This would make sense if the droplets were negatively charged as they would move away from the negative electrode or the removal of the positively charged field keeping them in the air caused them to drop out.

Taking another step down the rabbit hole, PH means the Potential of (positively charged) Hydrogen ions in the water/solution. It is a negative log scale, meaning it is non-linear, and the lower the number of positive hydrogen ions, the higher the reading. With a zero potential, you would basically have hydrogen ion soup.

This is in line with the negatively charged ions from an ion generator making the PH rise if they (temporarily) neutralised a number of the positively charged hydrogen ions.

Now I need to find out what lightning does to the charge in an area. Logically, as it caused a PH drop, it should be a huge whack of positively charged ions that suffused the solution decreasing the PH and the ORP, which I see from the diagram measures negatively charged electrons.

I will now google lightning, hehe.

EDIT :

So, it seems lightning can be both positive and negative, although one type is 20 times more likely than the other. Looking at your graph, we can figure out that you had the rare positive type of strike as it lowered your PH, meaning the electrical potential of your solution was lowered relative to the environment. This means the environment must have become more positively charged (to reduce the potential relative to a positive ion), which is the opposite of most strikes.

It also explains the ORP result and the different recovery rates. e- charge will be eliminated with application of a positive charge and will need to have their numbers built back up, whereas the hydrogen ions just need to regain their charge (subtly different process). It seems these different processes take different amounts of time, probably due to environmental factors like just how earthed the solution is which determine the rise rates. static charge (e-) will not rise quickly in an earthed solution, whereas this should not affect the PH rise.

Just typing this off the top of my head in the morning after a coffee so it may just be ‘morning bollocks’ as I call it


EDIT 2 :

If this effect is in play, when you use your HPA and turn your solution to a mist, you may be getting incorrect PH readings from it for up to a minute or two. Readings which can be up to a whole PH point too high


To double check, I would suggest to get some run-off and store it for a little while in an earthed container and see if the PH drops. If it does not change then the readings are fine, if it does then you are partly reading the negative charge in the solution, not the PH.

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62

Interesting ideas! I can easily ground the water I collect from the root chamber and check that out, but I need more coffee before I can think this through clearly :slight_smile:

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63

Oh, I don’t know. I know you’ve seen this fun experiment:

By the way, it’s funny how things come full-circle. As a youngster, I used to like pyrotechnics. As an adult, still like pyrotechnics but it’s more accidental now. :smile:

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64

I like this experiment. This will be very useful knowledge if it turns out to affect the PH.

https://web-material3.yokogawa.com/2015-07-1497_Pure_Water_WhitePaper_v2.pdf

Static Charges
Since pure water is a poor electrical conductor because
the conductivity is very low, it creates a static charge
when flowing past non-conducting materials that affect
the pH reference sensor. This static charge will create
stray currents resulting in erratic pH readings.
Pure water has a conductivity value of 0.055 ÎŒS (18.2
Mohm) at 25ÂșC. This liquid resistance can lead to the
formation of surface static charges. This can generate
“streaming potentials” (stray currents that can mimic pH)
in the solution which may cause large errors, or at least
excessive noise in the readings. A low impedance, well-
shielded and grounded electrode can lower these errors
to a minimal value, usually less than ±0.05 pH units.
Because the electrical resistance of a typical measuring
cell is so high, the electronics used to measure the cell
potential are very susceptible to additional interfering
factors - extraneous electrical noise pickup and hand
capacitance effects. These static charges, called
streaming or friction potentials, are comparable to
rubbing a glass rod (glass electrode) with a wool cloth
(the water). This high resistance also increases the
measurement loop’s sensitivity to surrounding electrical
noise sources. (Figure 11)

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65

My single regret is that I have only one like to give.

EDIT :

Of course, the higher the nutrient concentration the lower the effect, because the solution is less able to hold a charge.

EDIT 2 :

@anon32470837 You should read that PDF Northern Loki posted, it will give you information that may alter your plan to put any sort of charged plate near your nutrient spray. Page 9, anionic and cationic water purifiers. It seems things like Mg and calcium are charged and will get pulled out and stuck to the plates. Probably other good stuff too.

been drinking rum, I will stop posting now.

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66

Proper oaked rum I hope? Not that white abomination of a moonshine?

:slight_smile:

This rabbit hole is very informative

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67

Of course, it was Wood’s Navy rum at 57% :slight_smile:

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68

Oh boy. Im gone a single day and the rabbit hole got a LOT deeper :wink:

Very interesting stuff. I need more time to go over some of these things you two have posted, but all this has me second guessing my decision to lower my rez PH to 4.6 to offset the rise in PH in my root chamber.

Now Im wondering if the PH rise in the mist is really “real” or not. It also occurred to me that even if the PH rise is real, the changes may not be happening instantly or as rapidly as I thought. Ive been having some odd issues with the plants, and I keep coming back to it could be PH related. Im now thinking that the mist could well b e coming out of the nozzles at the same PH it was in the tank, and its still at that PH (or very close) when it hits the roots. Then, after some time passes and it collects in the bottom of the root chamber, it starts raising up.

The PH in the collection jar I catch the runoff in doesnt change when I ground it, so I dont think that part is an issue - but there are some other aspects to this discussion that may well be factors


So, more testing is under way


By the way - this so called “off topic” diversion is turning out to be pretty much “on topic” after all!! :slight_smile:

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69

I would probably start by taking samples from each stage if possible, give them time to settle, and then measure the PH of each sample and compare them to ‘live’ readings.

Then at least you will be able to eliminate or confirm whether static is affecting the readings and have a clue as to the speed of whatever PH change is happening.

You could do with one of my doser/loggers. Then you could graph any PH change in a sample over time, compare that to the EC changes, if any and have up to 8 PH probes and 8 EC probes to sample at any point you like. You could also pick any point in your water delivery and regulate PH and EC at that point on the fly.

Really helps when figuring stuff like this out.

I only wish I could afford to build more than the two prototypes I am developing on. One is constantly in real world use, the other is for development and testing. When the test unit is stable, I swap them over and incorporate all the newer features into the older model. Then that becomes the test/dev unit.

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70

I am doing that everywhere I can. The one part I cant read “live” is the mist itself. Its just to thin to register on my PH tester. The flow rate is also so slow that it takes an hours or so to collect enough to cover the glass bulb. Thats more than enough time for changes to occur that I cant monitor.

The PH seems to be stable once the water leaves the rez and gets into the accumulator tank and it reads the same when I pull samples from different parts of the system between the pump, tank, and nozzles.

Once it leaves the nozzles, I cant check it until enough collects to cover the bulb on the tester.

I think Im just going to have to make changes and wait to see how the plants respond. The leaves seem to wilt pretty quickly. Hopefully, they will UN-wilt just as fast :slight_smile:

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71

Well, it turns out, at least with HPA systems, or maybe just my system, you cant judge PH by the runoff water.

I raised the PH in the rez and accumulator tank from 4.7/4.8 to 5.4/5,5 range this morning, and the plant loves it! Its already recovering nicely in just a few hours with significant new root growth.

The rez, tank, and the entire sealed system all reads the same - 5.4/5.5, but the run off is now reading 6.4/6.5. I let samples from the rez, tank, feed line to the solenoids, and the run off sample sit for over an hour with no change in readings.

So - that leaves at least a few unanswered questions.

  1. Why is my run off PH so much higher?

  2. How can I measure the PH of the droplets that actually get to the roots?

I’ll tackle the easy one first - #2. I dont see any way to do that, so no point in worrying about it. I will just have to look at how the plants are doing and make my best guess. I will still monitor the rez and run off so I can see if anything changes, but thats about the only thing I can think to do.

Number 1 is trickier. We have discussed several things so far that may be contributing.

I doubt its static charge, because the increased PH doesnt change over time. If it was due to static charge, I would expect it to go back down after the charge bleeds off. I see no changes after over an hour of sitting, or if I put a grounded wire in the solution.

I dont think its the Lenard Effect either. If I am understanding it correctly, that still basically just a static charge on the droplets. The difference being that different sized roplets have opposite charges, rather than all the droplets having the same charge. So, I would expect that the charged droplets would neutralize each other when the droplets collect in the bottom of the rez. The Lenard Effect is supposed to charge small droplets negatively, and larger ones positively. Surely the charges would cancel each other out when the droplets joined back up together.

The other possibility is back to CO2 exchange - going back to the PDF that discussed PH changes in swimming pools due to co2 changes, carbolic acid, etc. I can see micro droplets haveing a much faster change rate than a liquid in a container. It would also tend to persist once the PH changes. This is the direction Im leaning at the moment - but thats just guess work really.

If anyone can think of any other tests to run, or has any other ideas, Im more than willing.

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72

I have an idea


You know how carbon dioxide is a Lewis acid, so maybe that is the kind of reaction you are experiencing?

If you bubble air through tap water, there will be more CO2 available in the air than dissolved in the water, some will dissolve, and form carbonic acid, thereby lowering the pH.

If you bubble air through water with a lot of carbonic acid already in it, some of it will dissolve in the air bubbles and leave the solution, thereby raising the pH.

It has been close to two decades since my last chemistry class, so I cannot say with any certainty whether this will apply to whatever you have in that solution, but that principle might.

Also, bubbling air through water offers a much smaller total area of surface contact than misting water through air, so the reactions, if in fact occurring, would be much faster and more complete IMHO

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73

Thats very close to what was presented in the PDF on pool maintenance that @Northern_Loki posted earlier in the thread. Im thinking you are on the right track.

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