Very different pH readings?

[MrRudeSnowman]

Hi,


I have PH indicator drops and that simple PH meter with one node that does not need calibration.

Big difference in readings. Drops are like a year old... would that impact the way they work?

Should meter at all be used to measure water PH?

I have AD12 coming in next week but still... seeds where planted today and i don't want to do any damage.

 

[dick23rk]

I would go by the meter as long as it was pre-calibrated properly. Try testing it in some white vinegar, I believe I remember someone saying that it has a ph of right around 4. That will give you a good idea at least to how close it is. I'm not really sure if the ph test drops go bad but that is what I am currently using. they may go bad if they are left out in the light or if they get to hot or cold possibly.

 

[415friendly]

How different is your meter reading from the drops?

Remember that drops are kind of subjective to how you really the colours.

It took me a while to believe my meter, but I back up all of my readings with ph indicators.

I use Bromothymol blue and Bromocresol green so I can verify ph readings between 5.5 and 6.0

 

[Major PITA]

Drops do degrade over time, but one year they should be accurate.
Some PH meters are garbage. I've never seen one that is accurate with a single probe.

 

[MrRudeSnowman]

How different is your meter reading from the drops?

Remember that drops are kind of subjective to how you really the colours.

It took me a while to believe my meter, but I back up all of my readings with ph indicators.

I use Bromothymol blue and Bromocresol green so I can verify ph readings between 5.5 and 6.0

Drops show lower levels. Meter i think is right to show ph 4 when put into diluted phosphoric acid i use to lower water ph level.

 

[415friendly]

It depends on how dilute your phosphoric acid is. A more dilute solution will have a higher pH, which is why it is important to pick up a calibration solution/ buffer.

I know the drops show different levels depending on the color they turn, but I sometimes have a hard time telling between yellow and yellowish green, which could be anywhere from 4-6 sometimes.

I calibrated my cheap pH meter with 7.0 buffer and use it for an estimate.

Bromocresol green is green color below pH of 5.4 but turns royal blue at 5.5+. I don't want my pH that low, but it verifies to me that my pH is above an acceptable minimum.
Bromothymol blue is yellow below 6.0 and green above that.

I usually add pH up until the meter says about 5.8-5.9, and then verify with the Bromothymol blue that the colour is still yellow, indicating that the pH hasn't crept too high or that my meter is way off.

I know you're running soil, which allows for a higher pH so the numbers you are looking for are a bit different.

 

[MrRudeSnowman]

415, thanks for your input.

Can any comparison be drawn between PH drops and Bromocresol/Bromothymol? Drops should show yellow color when PH is at 6,5.

Anyways, i see your method is quite smart much more fail safe.

I just now realized that soil has to be right PH and if it isn't not much can be done in a sense that simple measurements show how long PH'd water can change PH in soil. And time is quite short. Lesson learned. It's just strange i was able to complete this many grows with no problems up til now.

It depends on how dilute your phosphoric acid is. A more dilute solution will have a higher pH, which is why it is important to pick up a calibration solution/ buffer.

I know the drops show different levels depending on the color they turn, but I sometimes have a hard time telling between yellow and yellowish green, which could be anywhere from 4-6 sometimes.

I calibrated my cheap pH meter with 7.0 buffer and use it for an estimate.

Bromocresol green is green color below pH of 5.4 but turns royal blue at 5.5+. I don't want my pH that low, but it verifies to me that my pH is above an acceptable minimum.
Bromothymol blue is yellow below 6.0 and green above that.

I usually add pH up until the meter says about 5.8-5.9, and then verify with the Bromothymol blue that the colour is still yellow, indicating that the pH hasn't crept too high or that my meter is way off.

I know you're running soil, which allows for a higher pH so the numbers you are looking for are a bit different.

 

[415friendly]

PH drops are just another pH indicator, but change to several different colours over a range of pHs, which makes it harder to decide where you are (for me at least) because you have to make a judgement call on what colour it matches up with.

With Bromocresol, if it's clearly blue the pH is above 5.5 but if it's kind of greenish, it's somewhere between 4 and 5.5.
With Bromothymol blue, if it's yellow, it's below 6 and if it's greenish, it's between 6 and 7.4.

They create the perfect combination for testing pH if you are aiming for around 5.7 or 5.8.

 

[MrRudeSnowman]

Ok so the AD12 tester came in. Now i use 10ml of dilluted PH down per 2L water instead of 14ml that i did before. Pretty big difference. Will see how it affects the new grow but all things considered i can see some improvements already. According to new meter i was using water of ph5... no wonder things where bad.

PH drops are just another pH indicator, but change to several different colours over a range of pHs, which makes it harder to decide where you are (for me at least) because you have to make a judgement call on what colour it matches up with.

With Bromocresol, if it's clearly blue the pH is above 5.5 but if it's kind of greenish, it's somewhere between 4 and 5.5.
With Bromothymol blue, if it's yellow, it's below 6 and if it's greenish, it's between 6 and 7.4.

They create the perfect combination for testing pH if you are aiming for around 5.7 or 5.8.