Plants and roots still look good, but Im not impressed with the amount of trichomes for this stage. Im at 5+ weeks of 12/12 and I had more trics on previous grows I think. Pics later.
Changing over to the weak Phosphoric acid - may - have made a very slight improvement in the rate of increase of the PH - maybe. If so, it wasnt much of a change. The Ph is still going up at essentially the same rate as before, or maybe a tad slower. For sure that was not any kind of ‘fix’, so probably not a problem that needed fixing.
Next time I re-fill, I will try @MicroDoser s trick with the strong base, but more of it. I almost did it this this last time by accident time with Advanced nutes, but not to the level he does.
In the mean time, I drained the rez, flushed the system and re-filled with Mega Crop v2. I want to see how it handles the RO + UV thing as well as how much better the new buffering is compared to Advanced Nutes.
I did NOT do anything with the PH Down/PH Up mixing this time. Just a straight re-fill with RO water.
I screwed up and added my usual dose of CalMag - 1 ml/gallon - by mistake, but did not do any PH Up/Down pre-treating of the RO. I wanted to try it without any extra calmag because they said they increased the amount in the mix. Next time… This new CalMag (no extra nitrogen) doesnt add much at all to the EC, but it does lower the PH - which is the opposite of how the GH CalMag did for me. Not sure if I like that or not, so I probably will switch back to GH CalMag next time I need some.
With the calmag and just Mega Crop v2, the initial PH is 5.5 at an EC of 1.0. We will see how this does…
I just checked all around the UV light in the rez, and I cant feel any change in the plastic of the tote where it is closest to the light. The suction cups are working great - much to my surprise. Ive been running the light 24/7 for about 10 days now, so not much time over all. I ordered an extra light to have as a back up. If this one dies, I dont want to wait to get another one in the rez.
The new Mega Crop is chunkier than the old stuff. V1 had little hard little balls of something, then most of the rest was fine powder. The new stuff doesnt have the same balls, but does have random sized white chunks of something.
That concerned me at first, because I normally only add a few grams - 5 to 10 maybe - to the rez at a time when Im mixing. Trying to get equal amounts of all the chunky stuff - in the proper ratios - into a small scoop just isnt practical. One time I would get no chunky stuff, and the next time a bunch.
So I took a large scoop - about 60 grams - and dissolved that into about 3/4 of a quart of RO water. It took a two or three minutes of shaking/mixing, but it all dissolved ok. Then I added small amounts of that mix to the rez until the EC was where I wanted it. This worked just fine. Im going to post this in the Mega Crop thread with a pic or two.
Here is a comparison between some Northern Lights I grew in soil last year and two buds on the C99.
Left most is the NL, center is the one of the best of the C99 buds and right is one of the worst. These are all about 38 days into flower. The NL may have been a tad younger by a day or so.
Maybe this is strain related, or maybe its my PH issues, or its just slow from all the earlier stress with copper, chlorine, brown zombies etc. ??
Edit: It occurs to me it would probably be a better comparison to another sativa mix. Here is one of my Blue Dream - also in hydro - at about the same age.
One thing I have thought is that I recirculate, which will bring my PH down as the plants excrete H- ions. In combination with the doser keeping things controlled, I have a growing doubt that my numbers are relevant when looking at a run to waste system.
I have started using this PH drop as a cue to do a partial refresh of my tank. I rationalise that it is a sign the plants have eaten a decent amount of the food available and the ratios of nutrients have been moved away from ideal. It is hard to tell but it seems like I am using roughly half the PH adjustment I was using before I started reading this thread.
We shall see what benefits this brings if any when it comes time to cut them down
I think everything you said makes good sense, but Im a little curious about this statement:
Is it that you are doing adjustments half as often - and so allowing a larger PH swing before the adjustment kicks in? Or are things running better, so that you only need to do them 1/2 as often?
Or?
The pressure snubber arrived today and I got it installed. Wow! What a difference in noise level from the pressure switch. The tank tops off a little faster than before, which makes sense if the power isnt getting cut on/off at a 60 hz rate at the end. The best part is the noise is waaaay down. The switch now has a nice clean sounding click at the end when the upper pressure is reached with just a hint of buzzing. Im really glad a decided to add this. Im sure the pressure switch will last much longer now and be more reliable in the mean time.
There is still some buzzing though, which means that some of the pressure pulses are still getting to the switch as it reaches the cut off pressure, even with the snubber.
I have no idea how much of an issue this may be when I convert to the arduino pressure switch setup. Im hoping that it will be a simple matter of an offset or doing some sort of averaging of data points. Maybe, once the pressure reaches the set value, wait a few miliseconds and sample again, to see if the pressure dropped back down, and then cut the power if it didnt? Are the pressure readings taken at set intervals or continuously? I guess it will depend on how big the pressure difference is. Might need to do some averaging. I notice that combo pressure/humidity/temp sensor @MicroDoser linked to above has a ‘smoothing’ option. That sounds like what I might need to do. I would think a loop comparing the hi and low pressure spikes would do it?
Mega Crop V2 report. V2 does seem to have more buffer capacity than V1, but it doesnt have the same buffer capacity that the Advanced nutes did. It holds PH fairly well for maybe 8 hours or so, but then it starts back up fairly fast. Once the PH starts going up, it is no faster than the Avanced though, so that is also an improvement over the V1.
The Mega Crop also seem to have less ‘stuff’ visible in the water than the Advanced did. Not 100% sure if thats good or bad. Im assuming visible stuff would be un-dissolved nutes or precipitates, so Im guessing less is better. Its to soon to tell if the plants like it better or not, but it is way easier to deal with during a rez re-fill/top-off than the three bottles of Advanced. Plus the cost is stupid lower.
Yeah, this is what I keep coming back to. There ‘should be’ nothing left in my rez that can drive the PH up, and yet it goes up fast once the buffering capacity is used up.
I have been thinking that it had to be dead or dying algae still in the tote or pipes or pumps. I cant think of any thing else that could be doing it. But - switching to RO, all the chlorine, copper, and now the UV light treatments, should have killed off the vast majority of that crap.
This got me to re-thinking things. I was about to go ahead and buy a new tote and all the related plumbing, but then I decided to test some Mega Crop I mixed up a few weeks ago when we were doing the buffer thread stuff. The sample has been sealed in a mason jar for more than two weeks. It had been reading around 5.6 or so and its now reading 6.1. When I stir it, I can see there has been a small amount of precipitation - which is something @Northern_Loki also noticed when the PH rose in his tests.
Then I remembered that the Mega Crop folks mentioned that their buffer was set to somewhere in the low 6’s - which is consistent with what Im seeing. So, the Mega Crop all by itself, with no action from algae or anything else, tends towards a PH around 6.1.
That makes me think, maybe I dont have an algae problem??
BUT - that does not explain whats going on with the Advanced nutes. Their MES buffer is supposed to be targeted at around 5.6-5.8, but it also wants to go to 6+ after a day or less.
So, if it inst algae driving the Advanced PH to go up, what is?
A new tote and some pipes and fittings will be under $20, so I will probably do that anyway, just to be sure.
Edit: I just mixed up some Advanced nutes in a mason jar and will see how they do sealed up over time. I am expecting them to settle in at a lower PH based on the MES buffer, but we will see…
The periodic refreshing of some nutrient solution means there is less H- ions so I need less PH up to counter that. I have kept the same hysteresis (PH range) and I still allow a swing of up to 0.1PH, it does seem that the doser is dosing less and the PH wanders in that 0.1 PH range more time than it used to.
I have also started doing three days at 5.85-5.95 (for Mg and macro nutrients) then a day at 5.45-5.55 (for zinc and other nutrients) and sometimes a day or two at 5.6-5.7 (just in case).
After a couple of those swings, I drop the PPM from 650 to 400 (which drains about 3/4 of the tank to the level of the pump as the inflow is less than the outflow) then put it back to 650. The largest swing from doing a tank refresh is a 250PPM drop for about 1 hour. PH etc remain within tolerances.
My suspicion is that if your PH swing is infection related then you will see a small benefit that will go away in a day or two. Unless you replace literally everything then there will be a vector of reinfection from the non-replaced kit. I think that even if you do replace literally everything then the air itself is a reinfection vector. It is seeming more likely you are just buffering at low 6’s and your PH will always drift towards that.
I had similar issues with mould one time. What I did was to get an ion generator (UV bulb in bazooka looking thing with a fan, created ozone) which made toxic air and I left it in the room for a couple of days. I reckon a bleach spray would have done as good and would have been a fraction of the price. It did get into soft furnishings without damaging them though.
From reading this thread and the other buffer one, I cannot off the top of my head think of a buffer that works in that range. The simplest answer is that they have the same buffer range as megacrop and are lying about it…
Just a thought, are there nutrients designed for run to waste instead of recirculating systems?
To my thinking they should have different buffers. The recirculating one being higher as it should be compensating for the PH drop from root action on the nutrient solution.
I don’t recall them noting that they’ve “set” their buffering at a specific PH. The only thing I’ve seen them publicly announce was that their formula is buffered. If you have a reference post on their buffer, please point that out as that will give us a starting point to discuss with them in the future on how they are accomplishing that. Perhaps you mean the PH of MC at a certain EC settles at a certain PH. This is different from the buffer (but the PH does effect the apparent buffer effect). But, even then, I see the initial PH at about 5 when added to RO water (for MC version 1 & high EC).
Naturally, from the formulation, the most obvious buffering component would be a phosphate buffer which has three pKa(s) of 2.1, 7.2, and 12.3. This does not mean the solution will tend to drift towards the pKa. What that means is that the buffering is the strongest near those values. For review, we are talking about the balance between H+ and OH-. If the PH moves, there is something in solution that is affecting the balance. A buffer acts to supply either H+ or OH- slowing the apparent change in the ratio between the two. This does not mean the PH is only at the pKa and it does not mean that the solution will drift towards the buffer pKa. All a buffer does is slow the apparent effect on PH after the addition of H+ or OH- ions (relative to a non-buffered solution). PH will change, just not as great of a change otherwise. The PH may more readily move one way or another non-linearly depending on which side of the pKa(s) the PH of the solution happens to be at.
The greater the concentration of the buffer, the more ability the buffer has to slow the change in the ratio. If anything in solution is reacting with the buffer, the buffer will eventually deplete on one side or the other of the pKa value. At some point there is no longer any buffering action. The further away from the pKa, the weaker the buffer (less capacity). This is the reason you want a buffer with a pKa value near your target PH.
If you take a buffer with a pKa value of 7.2 and adjust the PH down to 5.8, you are more than 1PH away from the pKa. This buffering at the 5.8 will be weak. You are more than a 1PH away from the pKa. Now if you were to slowly increase the PH back towards the 7.2, you would see the buffering action increase slowing the change of the PH. It would reach the maximum buffering effect at 7.2. As you exceed this value you’d again see the buffering action slowly decrease.
Note: In reality, a complex mixture of chemistry will probably have a variety of buffering effects at a variety of pKa values as the ions form a variety of different complexes with the H+ and OH- ions and the available salts (Na, K, etc). Sometime that might produce an insoluable precipitant (bad) or a soluble precipitant (maybe ok).
MES may be a sensible guess but MES is expensive and, if they are using MES, it is also likely that the concentration is low. Could be a combination of buffers, MES + citrate + phosphate. Don’t know since AN likes to call things “proprietary”.
The greater the concentration of a buffer the greater the capacity it has to buffer against a change in the quantity of H+ or OH- ions. It becomes “stronger”. It has more “capacity”.
However, you can’t just up the concentration without being thoughtful. For instance, a phosphate buffer is also a nutrient source. If you were to increase the concentration of a phosphate buffer, you’d also be altering the nutrient ratios. Obviously, at some point, it could have adverse effects.
For nutrient formulations, the addition of monopotassium phosphate will give you a buffer. It will be weak at the target PH because it is greater than 1PH from the pKa and the concentration is limited for plant health. The buffering provided, in essence, is a bonus that is gained by using this particular chemistry as opposed to something else.
If the quantity of buffer available in solution is low, the “capacity” of the buffering effect will likewise be low.
Take a critical look at the curves in the buffering experiment thread. Notice how the MC(v1) is buffering. (perhaps, I’ll titrate some AN to compare. Let me know what you are using). Then, take a look at some of the other curves and note how they change as the concentration of the buffer is increase. Particularly, note how the location of the pKa values of the buffer becomes more obvious as the concentrations increase.
The best choice of a buffer for a particular situation has the following features:
pKa near your target PH
allows high concentration before phytotoxicity
does not sequester/cause precipitation of desired nutrients.
Any chelation of salts is synergistic (e.g. keeps nutrients plant available)
To start, there are only a few standard buffers that will meet (1). MES appears to be the most promising at the moment. Just so happens the pKa is ~6.15 (temperature dependent). +/- 1PH provides buffering in the region ~5.15 - 7.15 with a suggested PH buffering range of 5.5-6.7 for a strong buffering effect.
I see how you are doing it now. That sounds like a good system you have set up.
I cant remember if I asked this before - how much PH down do you think you add between rez changes?
Im asking because one of the reasons I have been wanting to find a better buffer was to reduce the amount of PH down Im using. As @Northern_Loki has pointed out, adding more phosphoric acid can mess with the phosphorous feed ratios.
Thats one reason I originally switched over to Sulfuric acid. From what I have read, the plants can tolerate excess sulfur pretty well - so the extra sulfuric acid doesnt unbalance the nutes.
But - if you are doing fine adding a lot of phosphoric acid, then maybe thats not as much a worry as I thought.
Yeah, thats the real question - is this PH rise just the nature of the beast with my nutes/water combination OR is it zombie algae related - OR - some of both.
So far, nothing I have done has really made a significant dent in the situation - which tells me I havent gotten to the bottom yet as far as WHY.
The RO water helped a good bit, the chlorine and then the UV helped some, changing to Advanced Nutes helped a lot, but only for a day or so, then its back to normal.
Arguments in favor of infection with algae or some other bacteria, is that adding chlorine did make a difference, and keeping the UV light on is continuing to make a difference. As you said above, there is certainly still some crud in the system that would be a re-infection vector.
The main argument on the other side - that its NOT infection related - is that the Mega Crop, and now the Advanced also, just seems to want to go to 6+ PH even if left in a sealed mason jar.
I started a sample of Advanced Nutes in a mason jar late yesterday. It mixed up at 5.7 PH. Tonight its at 5.9 PH. Thats about the same PH rise I see in the rez over that same time period. The only difference is I add calmag initially in the rez, which makes the starting PH closer to 5.5. After the first 24 hours the rez is usually up to 5.7, so the same .2 rise in PH in a sealed jar as in the rez. Thats after just one day. It looks to me like the Advanced is going to do the same thing the Mega Crop is doing - go up into the low 6’s all by itself in a completely sealed system.
So, I have ‘evidence’ that seems to be pointing to infection, and other ‘evidence’ that the nutes just do things this way no matter what.
Im going to go ahead and replace the tote and all the plumbing up to the pressure pumps. Thats as far as I can go in a short time. I dont want to leave the roots to dry out. The tank holds enough to run the misters as long as 36 hours or so, but I cant easily replace anything after the pumps without re-doing the plumbing significantly. That will have to wait. That should tell me if there is something in the rez and those pipes causing or contributing to the PH rise. It may only last a day or so, but it will be a good data point.
The Advanced feed chart doesnt distinguish between drain to waste or recirculating - just the one chart. I would assume it assumes recirculating as thats what the majority of folks do.
I got that from an email they sent, but in looking back on it, they were not really clear. Here is what they said when I emailed about buffering.
This is what I got:
New MC formula released last month has improvements in bufferings. Also, the range for Mega Crop is 5.5 - 6.5 pH.
I am sure I found an MSDS somewhere that listed MES as one of their ingredients - but now I cant find it again, so maybe Im mis-remembering? I figured that was the reason they were so $$ was the MES.
The stuff you post on buffering it starting to make more and more sense to me. I think its finally starting to sink in somewhat, because I was able to follow almost all of that fairly easily this time around.
Yeah, so far MES looks like the ticket to me too - but the $$$$ is a killer. Plus - which variation of MES should be used? I have found at least three different ones listed in the buffer calculators on-line. Plain MES (I think the acid form?), MES Sodium Salts, and MES Potassium Salts.
It looks like the plain MES can be used alone or with one of the others? Thats not clear to me yet.
The target PH of the buffer can be adjusted as @Northern_Loki said above. I found a few websites with buffer calculators that allow you to pick which buffers you want to use, then calculate what amounts of the two (strong base/weak acid, etc) to mix together to get your target PH.
BUT - none of these tell you how much is tooooo much for the plants, so Im not sure how useful they will be other than as a guideline for mixing ratios.
Thats a pretty expensive test to do - but Im using the Advanced Nutes PH Perfect Micro, Grow, and Bloom three pack. Three quarts runs around $35
I think I need to pin down what the source of the problem is better - before spending more money on possible solutions.
So far, it looks to me like the natural tendency of both Mega Crop and Advanced nutes (when mixed with my RO water at low EC values - below 1.2mS) is to start around 5.6-5.7 and then rise up to the low 6 PH range within a few hours.
Is that just the way both of them work - or - is my RO water a factor as well. From what I have read, RO does not always remove all the carbonates in the water, so that could be a factor as well. I dont see any way to address that problem though other than buying hundreds of gallons of distilled water for every grow - which is a non-starter.
Add to that that I also seem to have algae crap in the air and water which will re-infect the system on an ongoing basis.
I am hoping that - if - I can clean the system well enough, that the UV light will prevent re-infection long enough to get through a grow cycle. But - thats still gong to leave me with the natural PH rise that either nutes do on their own.
Using MES as a buffer is just going to add too much cost to my grows, so Im stuck using either phosphoric or sulfuric acid. I cant tell if there is any significant difference in how long the PH holds between the two acids. The phosphoric may be a tiny bit better, but that may just be my imagination because the mix I have is stronger than the sulfuric. The sulfuric should be safer as far as phosphorous toxicity goes, but maybe thats not really that much of an issue.
Speaking of MES costs - the question is what molarity is needed to do what I want?
Those calculators start with a molarity of 0.5 for the MES. That works out to just under 4 kg of MES for 40 liters of solution = one rez volume for me.
Over an 8 week grow, Im going to use roughly 300 liters total. Thats roughly 25 killograms of MES. A quick search on ebay says that will cost $2100. Thats just a tad $$ for me
But - do I NEED 0.5 molarity or can I get by with a lot less? Or, would the salt versions do better?
I can get 100 grams for $20 from that same guy, so I may try that just to see how much it takes to slow this stuff down. 100 grams would have a molarity of .0134. Thats going to get very $$ if I have t do that every few days.
I have a 5l bucket with about 300ml of KOH in it. This lasts well over 6 months. After the first three months I top it off with some more water so I can dose more accurately, 300ml/5l is still a bit strong, to be honest. I used to add far more PH down when I ran with tap water, then the tendency was to always drift upwards, now I run RO the small amount of H- ions shifts that to a mainly downward trend after a day or two so I use dramatically less PH down. It has made about 0.2GPW difference to the system overall.
OK, to be sure whether it is an infection or not you need to have some water, nutrients, and a sealable container you know has no infection in it. I would say to get a glass jar, like a kilner jar, that you can sterilise with tablets or put in the oven (or both). Sterilise some water, either by boiling it or using some sort of tablet (boiling probably better). Dose and PH adjust the water, fill to nearly the top to eliminate the CO2 effect from the air, seal and observe. If a sealed container does not change PH then you know it is something external to the solution. If it changes, you know it is something in the nutes and PH adjuster (or the ratio of those items).
If you find the effect is external then you could half fill the jar and shake it regularly to see if it is CO2 or infection. If it’s the nutes, it’s the nutes…
As controls you could have plain water, PH adjusted water, and water not PH adjusted with nutes in.
By eliminating the effects from various areas, then observing the results, it should allow you to eliminate false causes for the PH drift and isolate the actual cause ( or causes ).
If you already have the jars, it would be free.
EDIT :
Yeah, if solutions to your problems are getting to those prices, it is cheaper to buy or build a doser and then you can go on holiday for a fornight and still monitor and care for your plants…
I still have the opinion that is where all this is going.
I think of a growing system like a drag car. Some people just take their daily drive to the track and see what it does. This is like growing in garden centre compost grow bags. Sure you will get a time (yield/result) but everyone around you will get a better time.
So you adapt your car, you add a turbo, better exhaust etc. In the grow world you may get LED lights, a better fan, change to hydro etc.
Eventually, you have a 2500HP funny car doing 5 second 1/4 miles. Or you are designing your own HPA system…
To my mind, advanced systems like the one you are designing are like top fuel drag cars. Every part needs to work in harmony with all the others just so the whole damn thing does not explode in your face half way through the run. You are monitoring your PH much mroe than a lot of people and you see why this is also required for your system. It is so highly tuned that small differences in PH make large differences in performance.
Without a doser, you are facing a LOT of monitoring, dosing, and fiddling to get things to stay within tolerances.
The electronic side is fairly easy, as is the code, but like growing it is an endless subject. Just like growing it is best to just start rather than research too much.
Glad my experimental results are matching those done by people with far more resources than me.
Im going to post some links and quotes here for future refference - so I dont forget
This one has some safe levels for MES and other interesting info.
Abstract
2-[N-morpholino]ethanesulfonic acid (MES) buffer or Amberlite DP-1 (cation-exchange resin beads) were used to stabilize substrate pH of passive-wicking, solid-matrix hydroponic systems in which small canopies of Brassica napus L. (CrGC 5-2, genome : ACaacc) were grown to maturity. Two concentrations of MES (5 or 10 mM) were included in Hoagland 1 nutrient solution. Alternatively, resin beads were incorporated into the 2 vermiculite : 1 perlite (v/v) growth medium at 6% or 12% of total substrate volume. Both strategies stabilized pH without toxic side effects on plants. Average seed yield rates for all four pH stabilization treatments (13.3 to 16.9 g m-2 day-1) were about double that of the control (8.2 g m-2 day-1), for which there was no attempt to buffer substrate pH. Both the highest canopy seed yield rate (16.9 g m-2 day-1) and the highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits. The pH stabilization methods tested did not significantly affect seed oil and protein contents.
Another one with interesting notes on MES and resins.
Plants grown in hydroponic culture make useful experimental models for soil-grown plants. However, a major problem of nutrient solution culture is the adequate buffering of solution pH. Four methods of controlling pH in hydroponic culture of winter wheat (Triticum uestivum L. ‘Centurk’) were compared at two levels of Ca (0.2 and 2.0 mM) to determine the buffering method with the least effect on the uptake of essential nutrient elements. These methods were: (i) manual titration with NaOH, (ii) Amberlite DP-1 weakly acidic cation exchange resin loaded with Ca, Mg, K, and H, (iii) the organic buffer, 2-(N-morpholino)ethanesulfonic acid (MES), at 1mM; and (iv) MES a t 5 mM. Five-millimolar MES gave the most consistent control of solution pH. However, it also inhibited Zn accumulation by wheat. One-millimolar MES did not maintain the solution pH as well as 5 mM MES, but it did not significantly alter the uptake of any essential nutrient element. It is recommended as a pH buffer for the hydroponic culture of winter wheat. Resin in membrane bags did not adequately buffer the solution pH. It also removed some Mn and Zn from solution, thus depressing their uptake by wheat. Resin in a pump system adequately buffered the solution pH until its effectiveness was limited by the flow rate through the resin bed. Adequate buffering of solution pH was found to be critical for experiments that study the interactions between Ca and other nutrient elements. With the pH buffer, MES, the previously reported effects of Ca on depressing Mg, Mn, and Zn accumulation were observed. However, in the poorly buffered treatments, these elements tended to increase slightly with increasing Ca levels, perhaps due to the effect of Ca on maintaining root membrane integrity in an acidic environment.
Sounds like they had nutrient deficiences if they restricted their PH to a value too strongly. This makes sense, I am settling on 80% of the time at 5.9, 20% at 5.4-5.6. I get an Mg def if I stay at 5.9, and pale plants if I stay at 5.4-5.6.
I’m interested in these for sure. Keep us posted what you hear.
In the meantime I’m re-reading all of this info from you guys on buffering. Going to take a bit of brainpower to make sense of all of this data. Good research guys and super informative.
I believe what is being said there is that MC is intended for optimal use at an adjusted PH between 5.5-6.5. They do not say what the effect will be if the PH falls outside of that range. Could be precipitation, I don’t know. I do not think they are equating improved buffering with the optimal PH range they’ve noted.
Without knowing what ingredients are being utilized as buffering complexes, we can not tell how they are answering the buffer question. We can look at the label and we’ll know right off the bat that the MKP (monopotassium phosphate) potentially creates a buffer. Addition of more MKP, for instance, will increase the buffer capacity. Although, that buffer (the phosphate buffer) has a fairly high pKa. It’ll do some buffering but it’s strength will be the best at a PH of 7.1. As the PH of the solution approaches 7.1, the change relative to the amount of OH- being added to solution will begin to slow. It’ll buffer at a PHs further away from 7.1 but the effect will be significantly less. E.g. buffers are generally considered good when the target PH is within +/- 1 PH of the buffer pKa. It may still have some buffering outside that range but it’ll be relatively weak.
Adding more MKP will improve the “capacity” across the entire buffering PH range. But, there are limits as discussed.
Sure, it’s a strong guess particularly if the MSDS calls it out. I have not seen the MSDS and would imagine it would say “proprietary”.
AN has not been known to keep their product profit margins reasonable. So, I’ll presume that they are using the minimal amount of MES in order to demonstrate that there is some buffering improvement. And, not much more. Though, this is pure conjecture on my part. There is an absurd patent that may be related to AN regarding the buffering of nutrient solutions that includes the use of MES.
So my point in these posts and responses is not to “tell” you to seek out of specific buffer but instead to clarify the understanding of how buffers works. Same with the experiment thread, just pointing out the effect and differences to those who dare to dig in. And, there are clear differences. That doesn’t mean “buffers” are good or the right thing. There are downsides, too. Same with the ION exchange resins. They are simply another tool.
Seemingly, it is difficult to decouple the intuitive feel for adjusting PH (whether automated or manually) from the use of a buffer. And, to describe the underlying theory. It is somewhat counter-intuitive and it has been my failing to describe it in a sensible manner. Once the concept clicks though, folk will have a much better feel to what, when, how, and why.
I’ll attempt describe buffering concepts in more detail in the buffer experiments thread shortly but for now the key takeaways are:
a buffer complex has one or more pKa values. This does NOT determine the PH of the solution.
a buffer complex has a capacity
a buffer complex consists of two conceptual components, an acid and a conjugate base
a buffer complex will “automagically” vary the ratio of the acid and it’s conjugate base as OH- and H+ ions enter solution. This is true of a carbonate buffer, a phosphate buffer, citrate, MES, etc.
0.5M would likely kill the plants. From the experimental papers that both you and I have referenced, you’ll note that the concentrations are in the 5 - 10 mM ranges or 0.005M. You’d need to dilute the 0.5M MES solution 1:100 to achieve 5mM. The 5mM is NOT necessarily what you would need, either.
For MES, the acid is MES free acid. The conjugates are the salts (potassium or sodium). But, you do not need to purchase both. A strong base will supply the potassium salt (e.g. KOH) and the OH- ions to create the conjugate to the acid directly in the solution! Vhat!?!? That is where things become counterintuitive. The pKa has not changed but the capacity has.
FWIW, 1 KG MES free acid can be had for ~$130 stateside. The molecular weight is 213.2g/mol. A 0.5M solution is 106.6g MES per liter. A 5mM solution is 1.066g per liter.
At the noted 300 liters of 5mM MES, you’d need 320g of MES ~= $42. And, again, this is NOT necessarily what one would want. While still not cheap, not $2100. That is FUD. This is where capacity and the unique situation comes into play. The what, when, how, and why are important to determine if it’ll be useful.
Thanks, I’ll probably just look at one of the stages such as the Bloom for the higher EC. Do you have a concentration you’d consider for later/extended stage?
Hmmm, or do they require a mix in the bloom stage?
edit: ok, I see. 7ml gallon of each at late bloom. blah.
That plus it looks like using any of these buffer techniques - MES, resins, other buffers - runs the risk of nute problems in the form of sequestering nutes, or precipitation, or what ever. Especially at hi concentrations.
I emailed Dow about the replacement for the Amberlite CG50.
I also found some for sale. This is the smallest qualtity I have found and the best price so far.
I remember it listing the quantity with a ridiculously wide range of possible concentrations - like between .01% and 30% or something like that. Ive noticed that many of the nute makers do something similar with their MSDS sheets.
And I want to thank you for that once again. I think my basic failing here is with the conjugates. Most times they say something like “and the conjugate salt” without actually telling what that salt is or explaining that its created automatically - like the MES “salts”. It seems like every time I try to track down a specific answer or detail, I get lost in other things.
That plus - as you have pointed out - this is a very complex chemistry situation with potentially many different, and interrelated reactions going on at the same time. I have a hard time keeping it all straight in my head.
I didnt catch the mM thing at first. That makes the MES use far more affordable as an option. It looks like as little as 1mM might even be effective, but that will need to be tested. I still have no real idea exactly how much upward pressure is being generated in my system, compared to the hydro systems in those papers, so trials would be needed.
That is a critical piece of the puzzle that I couldnt find. Thanks!
Ok, this is still a problem for me. In some of those buffer calculators, they have the acid as one item and the conjugate as a second thing that are mixed together. You change the relative concentrations to change the PH of the final solution. Is that not changing the pKa? Some of the combinations are listed as variable PH, and some are not.
Do you have a link for that pricing on MES? I havent found any that cheap. I might be willing to fork that much over to do some tests.
It looks to me like if I stay under 5mM I should be more or less safe for some initial testing.
Yeah, they insist on using all three. Dont go to that expense. I wont be using the Advanced any more once this runs out anyway. Im going back to Mega Crop or possibly one of the other salt based nute combos. Im going to concentrate more on using MES or a resin to tackle this issue.
If I can get MES, and the required amounts are as low as it looks like it might be, then it will be cheaper to use Mega Crop plus MES, then using Advanced by itself - maybe
It appears, from the titrations we’ve tried, it would be far more effective than the phosphate or citrate buffers. The minimal concentration I’ve titrated is at the 5mM concentration. Yes, it would need to be tested.
Yes, a potential problem. There is the possibility of something similar no matter the technique. Both chemical buffers and resins are doing similar things as they are both exchanging ions. Use of either could require some adjustments to account for any non-plant available chemistry generated. A precipitant, if it were to occur, would be the clearest and example of loosing something out of the available nutrients.
Oh, we can’t figure it theoretically out without lots of computation. We can only go by estimates starting with simplification, then, along with experimentation.
Yes, you can change the PH. No, that does not change the pKa. pKa is a definition based on the specific substance when 1/2 of the substance has disassociated. You loose capacity to buffer as you move away from the pKa(s).
It is not easy to describe without injecting further confusing terminology. We’d likely get into diassociation constants, capacity, weak vs strong acids, and conjugates. I need to formulate a better treatment on the subject otherwise I fear I’ll further muddy the concepts without first looking at the background. You’ll have to trust me for the moment when I claim that a buffer is the strongest (highest capacity) when the PH == the pKa.
For now, here is a graph of the buffering capacity of acetic acid vs PH (ignore the extremes).
Acetic acid has a pKa of 4.75.
I was following that until realized you said you use KOH - thats a strong base, so PH Up. I was more interested in the PH Down product. Did you mean Phosphoric acid?
Excellent ideas for testing! Thanks!
Yeah, a doser is on my bucket list for sure Im going to have to work up to that slowly though. Im going to start on that in small pieces - with that Arduino relay/timer setup first. Then when my current PH meter dies, or I get some extra cash set aside, I’ll start on the PH meter/doser setup. The meter portion should be easy. There are examples on the web for the software that I can use. I can work on the doser part a little at a time.
LOL Thats me. m addicted to fiddling with or adding tech just for the sake of the tech in some cases, or just to see fuzzy roots
When I first heard about PH swings being ‘good’ for growing, I was sure that was “stoner science”. Partly because I first read it from someone who couldnt put a coherent sentence together, never believed in periods, capitol letters, grammar, etc, and obviously new nothing beyond second grade science, and/or they were stoned to the gills :D.
Very good find! Those guys are far cheaper than any other source I have seen so far. Interesting to me that they still dont show up on my Google searches.
Ah! That clears up so much!!! I was thinking of the pKa as a value of the two buffer components AFTER they were in combination - not the individual components. I just re-read that section in the buffer calculator and its clear you just adjust to the desired PH after mixing by adding a base or acid as needed. . Thats what had me confused. Thanks!!
Im not toooo worried about that. So far, all the reports Ive read seem to talk about problems occurring closer to 10mM. As long as Im careful not to go above 5mM I think I will be fine - maybe
On the other hand, too hi a PH has its own nute problems, so either way I have issues. The trick will be to find the minimum that works.
Well, that plus trying to eliminate or reduce as many other sources - algae - of the upward PH drift as I can.
