A "how-to" guide on acidification

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Steve Johnson
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A "how-to" guide on acidification

Post by Steve Johnson »

Hard tap/well water is a fact of life for many -- if it's left untreated, minerals build up in the pot, slowly robbing our plants of their optimal ability to take up water and nutrients through the roots. But if you water your cacti and succulents with acidified water, they'll thank you for it many times over. To get the full benefits of acidification, some way of testing the pH will be important. Without that crucial bit 'o info, you won't know if your acidification is just right, too much, or not enough. The first method is easiest, using colorimetric indicator dyes you can buy at any hydroponic store. Unfortunately they're also inaccurate, and by quite a bit. The other -- and much better -- method is a pH meter.

Before we get into the heart of this presentation, I'll briefly mention that among the acids we can get, 5% white vinegar and citric acid are the best acidifiers for hobbyists because they're safe for home use. Large-scale collections and nurseries use stronger, more concentrated acids due to the large volumes of water required. These acids need very careful handling, so I'll leave that up to the professional growers who know what they're doing.

When I started acidifying my water in early 2012, Darryl Craig (CoronaCactus Nursery) was still active on the forum, and he said "a pH meter is the only way to go". He was spot-on about that, and the results have been speaking for themselves ever since (many thanks wherever you are, Darryl! :)). Now, which meter should we select? After doing a fair amount of research, I decided on a Milwaukee Instruments pH 600 pen-style digital meter, available on Amazon here. At $21.95, IMO a great buy for the money since it can be calibrated for accuracy (the other pen-style meters I found didn't have this feature). Here's what you'll get coming out of the box:

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The screwdriver's purpose will be obvious once you start using it. The meter also comes with instructions -- not difficult to figure out, but please follow them. (Any negative reviews you see on Amazon were generated by people who clearly weren't paying attention in class! :roll: ) An important thing to note in the instructions is that the meter's electrode should not be allowed to stay dry for extended periods of time. I kept my first meter in an open jar with some water, but I had a bad habit of forgetting to refill it before the jar went dry. After enough times of making that mistake, the electrode finally pooped out, so I had to buy another pH 600. If there was a way to cover the jar, evaporation wouldn't be a problem, but what to do? Hmmmmm... :-k There's the answer -- a jar with a plastic lid. In my case, an empty coffee jar:

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If you cut the hole to the proper fit, you're all set:

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It'll take a verrrrrrry long time before you lose too much water to evaporation, so this arrangement is a wonderful way to keep the electrode wet without having to constantly "babysit" the water level. Here's another important note you'll see in the instructions -- distilled water will ruin the electrode, and it's the ions in plain old tap water that'll keep it going. The initial calibration procedure sets the meter to 7.0 (pH-neutral), but the pH tends to creep up a little when you store it in the water jar. When you buy your pH 600, you'll also need to buy a bottle of 7.0 reference solution (available on Amazon here or at your local hydroponic shop). The reference solution and the screwdriver that came with the meter will allow you to calibrate it back to 7.0 right before you test your acidified water. And that, my friends, is how you get accurate readings. Now I'll give you some of my own instructions on the preparation of acidified water as it is properly tested with a pH meter:
  • Fertilizers tend to lower the pH a little, so whenever you fertilize, put your fert into the water first, then start with a small amount of vinegar or citric acid. Sources discussing acidification recommend a fairly wide pH target range of 5.0 - 6.0, so check the meter's reading and continue adding acidifier until you hit your desired target. If it goes below 5.0, you've over-acidified -- dump out the water and begin the process again. Once you determine the right amount of the acidifier you'll use, write it down for future reference.
  • The pH of tap water can sometimes fluctuate (usually higher in summer and winter than spring and fall), so it's a good idea to periodically test the pH of your acidified water. Not sure that we need to do this every single time we water our plants, but it should be a standard part of your practice every 2-3 months and/or when you skip on the fert from time to time.
  • Although potting media don't have a pH factor when they're dry, they can alter the pH of the water being taken up by the roots of our plants. For those of us OCD-driven growers who don't like to guess about anything, here's an extra step you can take:

    A. Fill an empty pot with your mix of choice and drench it through and through.
    B. Capture the runoff in a container -- make sure you have plenty.
    C. Filter the runoff with a paper coffee filter and funnel.
    D. Now that you have clean runoff water, test it with your meter, and you'll get the final pH.
What we're doing here is essentially a "slurry test" to determine if the mix has a neutral, slightly alkaline, or slightly acidic effect on the water going to the roots. Ideally, the runoff water should be approximately pH 5.5. If it's above 6.0, add a little more acidifier. If it's below 5.0, reduce the amount. Once you determine the correct amount, you'll need to run the slurry test only once unless you change your mix.

And finally, the pH 600 is a rugged, reliable instrument -- treat it well, and your meter should last a good long time.
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Aloinopsis
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Re: A "how-to" guide on acidification

Post by Aloinopsis »

Steve Johnson wrote: Sun Sep 08, 2019 6:06 pm"a pH meter is the only way to go"
You can also use pH test strips designed for aquarium use, culinary use, or medical use (such as for measuring urine pH, common in urologists' offices). I've used the aquarium and medical ones over the years with excellent results. They're just as accurate as a pH meter, easier to handle, and biodegradable so you can just put them in the compost. There's nothing wrong with a pH meter, but it's not the only or best way to measure water's pH.
DaveW
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Re: A "how-to" guide on acidification

Post by DaveW »

You can get test strips off EBAY too.

https://www.ebay.co.uk/sch/i.html?_odkw ... s&_sacat=0

I bought a cheapo test meter and it did not work properly. Maybe it was just faulty, but gave correct reading for tap water but crazy reading for rain water when tested against test strips. So I occasionally just use test strips now.

https://www.ebay.co.uk/sch/i.html?_odkw ... s&_sacat=0

As usual it depends on how often you use them. If you are constantly acidifying tap water a meter is the best bet, but I use rainwater which is usually slightly acid therefore don't need to routinely test or acidify. However adding fertiliser to the water can upset the PH of rainwater.

If you want to test the PH of your soil you should mix it with distilled water not tap water, such as that sold for topping up car batteries or from a dehumidifier, even maybe from defrosting the fridge, otherwise you will also be testing the PH of the mixing water and not just the soil.

The problem with these type of meters below I find is the soil in our pots is usually too dry since they work on galnanic action plus the probe does not go deep enough to get an accurate reading.

https://www.ebay.co.uk/itm/3-in1-Soil-T ... e1dca23203
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Steve Johnson
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Re: A "how-to" guide on acidification

Post by Steve Johnson »

DaveW wrote: Tue Sep 10, 2019 2:06 pmIf you want to test the PH of your soil you should mix it with distilled water not tap water, such as that sold for topping up car batteries or from a dehumidifier, even maybe from defrosting the fridge, otherwise you will also be testing the PH of the mixing water and not just the soil.
Or you can do some math -- for example:

I grow the vast majority of my cacti in pumice and granite gravel, so I wanted to see what its pH factor would be using the slurry test. For this test, I acidified my tap water down to a pH of 5.5. After saturation the runoff water was 6.1, and that told me the mineral mix is slightly alkaline with a pH factor of plus 0.6. Lower the pH of the acidified water to 4.9, and it'll be 5.5 when the mix is saturated. This is important to know because the pH will rebound as the mix dries
out -- using the runoff water from my slurry test, it rebounded up from 5.5 to 6.3 after 5 days.

If I started out using acidified water with a pH of 6.0, it would be 6.6 in the mix, then after 5 days of rebound it would be 7.4 -- at that point negating the benefit of acidification. Acid (in this case vinegar) neutralizes the minerals in hard water, and while the chemistry behind it is a bit complicated, pH rebound is a fact -- and a factor we need to take into account when we determine the pH of the acidified water we give to our plants.

By the way -- I tried using test strips a number of years ago, and the ones I got were never accurate. Impractical using them for a soil-less mix anyway, but for those of you who do well with test strips and you have soil in your mix, I'd be interested in your experience with pH rebound.
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DaveW
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Re: A "how-to" guide on acidification

Post by DaveW »

I'm no good at maths Steve, I quickly run out of fingers and toes. :D
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TimN
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Re: A "how-to" guide on acidification

Post by TimN »

Depending on what the pH of your water source is vinegar may be fine. My tap water (what rain?) is 8+ straight out of the tap. I would need a LOT of white vinegar to acidulate 30+ gallons of 8+ pH water. On the other hand, I use citric acid because it is also safe for home use and I need less than three tablespoons to reduce acidity down to the 5.0 range, assuming no fertilizer.

It has the additional benefits of being cheap (if you buy it right, i.e. don't go to a health food or hydroponic store), far more compact for storage and it doesn't smell like pickles.

I've only ever used a meter to test the water. After 10 years the formula hasn't changed much, but I do check occasionally. I changed fertilizers recently so I've been testing every batch of water.
Disclaimer: I'm in sunny Arizona, so any advice I give may not apply in your circumstances.

Tim
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Steve Johnson
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Re: A "how-to" guide on acidification

Post by Steve Johnson »

TimN wrote: Tue Nov 05, 2019 10:36 pm Depending on what the pH of your water source is vinegar may be fine. My tap water (what rain?) is 8+ straight out of the tap. I would need a LOT of white vinegar to acidulate 30+ gallons of 8+ pH water. On the other hand, I use citric acid because it is also safe for home use and I need less than three tablespoons to reduce acidity down to the 5.0 range, assuming no fertilizer.

It has the additional benefits of being cheap (if you buy it right, i.e. don't go to a health food or hydroponic store), far more compact for storage and it doesn't smell like pickles.

I've only ever used a meter to test the water. After 10 years the formula hasn't changed much, but I do check occasionally. I changed fertilizers recently so I've been testing every batch of water.
Good tip on citric acid, and the safety aspect is definitely a plus for larger collections like yours. Thanks for sharing it, Tim!
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WayneByerly
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Re: A "how-to" guide on acidification

Post by WayneByerly »

Oh! Steve

This is too, too funny ... let me show you how I did this.
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K
K

When I saw your first picture, I was confused. I thought you had made use of one of my pictures. And I thought how the heck did he get hold of one of my pictures?

Too, too funny!

I used the shorter container because a bottle of Test Meter Calibration Fluid (that keeps the meter end wet AND provides a way to calibrate your meter to an exact pH level) fills my container to almost the exact proper depth for the hole cut in the top of the container. I made it fit exactly by wrapping a layer of tape around it several times to keep it from dropping any further down into the hole that I cut in the plastic lid. Between the depth of the fluid in the container, and the tape wrapped around the meter, the end of the meter drops down to the exact proper depth.
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Make the moral choice & always do what's right. Be a good example. Be part of the solution & make a contribution to society, or be part of the problem & end your life with nothing but regrets. Live a life you can be proud of! Zone 7a
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Steve Johnson
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Re: A "how-to" guide on acidification

Post by Steve Johnson »

WayneByerly wrote: Sat Nov 16, 2019 3:27 pmI used the shorter container because a bottle of Test Meter Calibration Fluid (that keeps the meter end wet AND provides a way to calibrate your meter to an exact pH level) fills my container to almost the exact proper depth for the hole cut in the top of the container. I made it fit exactly by wrapping a layer of tape around it several times to keep it from dropping any further down into the hole that I cut in the plastic lid. Between the depth of the fluid in the container, and the tape wrapped around the meter, the end of the meter drops down to the exact proper depth.
20191116_100337-1024x768.jpg
That's a clever setup, and keeping the meter in 7.0 reference solution does make things easier than the way I've been doing it. If I can find a plastic container like yours (maybe a little deeper), I'll have to "steal" your idea. Thanks, Wayne!
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Re: A "how-to" guide on acidification

Post by WayneByerly »

DaveW wrote: Tue Sep 10, 2019 9:28 pm I'm no good at maths Steve, I quickly run out of fingers and toes. :D
Toes? You mean I could use my toes too? Oh man! All these years when I could have been using my toes too! This place is a veritable storehouse of knowledge! :shock: :lol: :wink:


The paragraph above is just another one of my idiotic attempts at being funny ... again ... (I think that somebody needs to kick my butt and tell me to stop that idiotic behavior)

But I'm like you Dave ... My general bent ... the way I do things, the way I approach MOST problems ... is more 'rule of thumb' than caliper measured rocket science. That is ONE of the reasons that I LOVE this place ... when there are people like Steve who are willing to take the time required to do all of the research necessary to come up with the details that are SO useful, SO necessary in taking care of our xeric plants.

There are a half-dozen/dozen of you guys here that have such an amazing knowledge base regarding the care of cactus, that it is just mind-numbing. You two guys, Elie ... and more (a proper complete list would just be too long), and I have such fantastic respect for you guys, SO much admiration for the truly vast extent of knowledge that you have accumulated. And then consent to take your time--out of what I assume is an otherwise very busy day--to share that knowledge with the rest of us (who didn't even know that we could use our toes too)--to help us take care of OUR collections.

I tell you, it's just astonishing. And I am SO grateful that I'm just tongue-tied. I cannot, not with any real degree of verisimilitude, express my thanks to you all..
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Re: A "how-to" guide on acidification

Post by WayneByerly »

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Last edited by WayneByerly on Mon Nov 18, 2019 9:27 am, edited 1 time in total.
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Re: A "how-to" guide on acidification

Post by WayneByerly »

Aloinopsis wrote: Tue Sep 10, 2019 11:09 am They're just as accurate as a pH meter, easier to handle, and biodegradable so you can just put them in the compost. There's nothing wrong with a pH meter, but it's not the only or best way to measure water's pH.
Just as accurate??? I am absolutely astonished that you can say that about something that you cannot even be SURE of what it is indicating. Easier to handle ... much, MUCH easier. Not the only or best ... I can't argue with that.

But, as politely as I may, without any rancor or personal attack, I am afraid I must disagree. Where is there a decimal place in a test strip? And there is NO way to calibrate a strip. I have used test strips where there was some question as to whether it was reading 5 or 6. AND, I have noticed enough of a difference between what a strip reads and what a meter reads to make me certain that there is no way to believe in the consistent accuracy of a strip ... not when there are discernable differences between what the two methods read.

I believe the difference between 6.0 and 5.5 IS significant. And I have elected to use a meter over test strips over rather significant differences between what a strip is "possibly" indicating and what a meter reads.

***************

Now, all that being said, there are a few things that I do by "rule of thumb", and NOT by using a caliper. There ARE things in the world that just do NOT require decimal point precision.

So, I suppose that If you do not believe that you require the precision of decimal points when measuring the pH of what you are feeding to the plants that you ostensibly care about ... then a strip is just fine.

I DO do some things by this "rule of thumb", but the most significant portion of my attitude about the tasks that I have to accomplish is this ... "do the best job that I possibly can in all things, from cutting the grass to accomplishing what was required of me at my place of employment.

***************

Using test strips instead of a meter is a "that's close enough" attitude. Which, as I said, is fine for some things, but not others. If a
"that's close enough" approach was used in taking care of my family then I would opine that I was doing a <explictive deleted> poor job in taking care of my family ... that I was NOT doing the best job that I could!

And I have a little more regard for my xeric plants than that.
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Re: A "how-to" guide on acidification

Post by DaveW »

Not sure you really need such accuracy Wayne, but no doubt nice if you get it. We used to be able to get narrow range indicator strips in the past that recorded PH in narrower increments, but the ones EBAY sell are much broader range. However I found them good enough for my purposes. However I use rainwater and I seldom run out in good old wet Britain therefore do not usually need to acidify tap water. I see narrow range indicator strips are available if you search for them:-

https://www.sigmaaldrich.com/catalog/pr ... &region=US

My problem was with a cheap test meter that I bought off EBAY. I tried it and it was OK with tap water, but when tried in the rainwater butt gave an obviously erroneous reading. Therefore I bought some cheap test strips and tried the tap water which agreed with the meter, but with the rainwater gave the reading I would expect from rainwater in the UK and another pond testing set gave the same readings. I have never weighed up why a cheap meter gave such weird readings and as I seldom need to test the rainwater I just use the cheap test strips. Also it is too much hassle keeping the meter calibrated.
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Re: A "how-to" guide on acidification

Post by WayneByerly »

i don't think i said it here, but i'll repeat it here. i think part of it depends on your own personal tendencies ... the way you run your life. I do the best job I can in almost everything I do ... so in those kinds of cases, a meter IS most appropriate ... but there ARE cases where the "rule of thumb" and not "rocket science calibration" is perfectly adequate.

My water comes from a well, and is therefore somewhat consistent in its pH ... so after almost a year of measuring the pH of my water and dispensing an appropriate amount of vinegar to "fix" it, I pretty know what the pH is going to be and adjust for the pH my experience has taught me ... without use of strips OR meter.

I AM of the opinion however that we DO need to duplicate the NATURAL environment of our xeric plants to the greatest extent possible ...

IF we DO care about our plants. but then we come back to our own personal tendencies ... rocket science or rule of thumb ... but personally speaking, I am EVERSO grateful for Steve's post here. Whether we use it or not, I believe we are all better off with as much information as we can gather.
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Re: A "how-to" guide on acidification

Post by RichR »

This is shifting the topic slightly, but do any of you do the same pH monitoring when you're sowing seeds? I have the same meter as Steve and it's reading distilled water at pH 9.0. Seems Awfully high for distilled water. If I put a few drops of Dyna gro fertilizer in a quart of distilled water it will change the ph back down in the 6 or 7 range.
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