Potassium Silicate - K2SiO3•nH2O

C

Castel

Member
I found 1 Kg of chemically pure Potassium Silicate (K2SiO3•nH2O) for under $10 from my chemical supply. It seems so many people are opting to rather purchase diluted solutions so I'm having trouble finding how much to add to my nutrient solution (Jacks 5-12-26).

The composition is:
K20 - 47-51%
K2O/SiO2 ratio 1.57 +/- 0.08

So trying to implement this in Hydrobuddy, I'm entering 49% as K20 and 31% as Si (given the 1.57 ratio of K2O to SiO2). I'm not sure if this is the correct way to enter it?

Anyhow, the only other person I have seen posting about adding pure Potassium Silicate was adding it to a Jacks 321 variation at 0.25g per gallon. This seems very low to me, and based on Hydrobuddy using the values above, at 0.25g per gallon provides the following PPMs:

K 8.059
Si 6.184

Jacks is already quite high in K, although I don't know at which PPM level K becomes toxic. Apparently it's nearly impossible to overdose Si however?

Anyone able to check my math? What would be a good target for Si PPMs in solution for coco?
 
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ruwtz

ruwtz

Well-Known Member
A lot of bottle products are at 80ppms Si or higher. AFAIK the generally accepted level is more like 35ppm's.

I use Agsil16H potassium silicate which is 32% K2O and 52.8% SiO2. Elemental conversion factor for silica is .47, so 1gram per gallon comes in at Si 66ppm and 71ppm.

580mg per gallon results in K 53ppm + Si 49ppm. This is a 7% solution, so close to Protekt.

Botanicare's Silica Blast is 2%.

A stock solution of 137g per quart and applied at 4ml/gallon ought to give you the same as Protekt.

I actually use mine as a pH up and K boost, which is particularly effective in late bloom to keep general plant health / quality up as she fades. I do not flush.

Can't speak for your system but i'm in coco drip dtw and K depletes incredibly quickly so I worry less about too much.
 
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ruwtz

ruwtz

Well-Known Member
Oh and watch that pH - it is very basic and will push you up over pH9. Add this to the res first, pH correct before adding your Jacks and anything else.

It will not play nice in solution with calcium or magnesium either.
 
C

Castel

Member
Thanks ruwtz. I'm also in coco DTW.

Agsil16 appears to somehow have a better SiO2 to K2O ratio than the reagent grade potassium silicate that I obtained. For mine, considering that SiO2 has a molar mass of 60 and K20 is 94, then 1 gram per gallon would provide me with 110ppm K and 62ppm Si. The math in my first post was incorrect.

I also read that around 30ppm Si is a good target. I was actually worried that I can't reach 30ppm Si without overdosing on K. At the moment my feed ppm at 6 weeks veg is roughly 100-40-190, and in order to achieve 30ppm SI, my K would jump to 240. Would that be within bounds for you?

And yes, I'm adding potassium silicate to the res first, then adjusting PH. Then adding calcium, magnesium, and finally Jacks. Nothing seems to fall out of solution.
 
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C

Castel

Member
Ok my math is wrong again. The compound I have is K2SiO3.

Molar mass of K2SiO3 = 154.2803 g/mol

Molecular weight calculation:
39.0983*2 + 28.0855 + 15.9994*3

Element / Symbol / Atomic Mass / # of Atoms / Mass Percent
Silicon / Si / 28.0855 / 1 / 18.204%
Oxygen / O / 15.9994 / 3 / 31.111%
Potassium / K / 39.0983 / 2 / 50.685%

So in terms of Si to K ratio, unfortunately this is even more unfavorable for me if I'm trying to limit K.

So at 1 gram per litre, I would have 182.04 ppm SI and 506.85 ppm K.

Hence to achieve 30 ppm Si in 1 gallon of water I would require 0.623 grams of K2SiO3 and my K would increase by 83.5 ppm.

Is my math finally correct?
 
ruwtz

ruwtz

Well-Known Member
I'm not checking your math, and you might be overthinking this one, but if you really are worried then ditch this compound and get regular agsil. All the work has already been done for you on that one.

I have stock solutions for all kinds of things if you're interested. MKP, MAP, potassium sulfate, ammonium sulfate etc.

I'm still tinkering with my nutrient profile and I will say it seems incredibly difficult to push potassium too hard in coco btw when you're counting every last ppm. I wouldn't worry about it, especially if you have your K:Mg:Ca ratios tuned pretty good.
 
H

Hookah79

Active Member
Hey Ruwtz,you said you have stock solutions for mkp and map can you help out with the formula?I use 880 gr jacks and 580 cal nit as a stock solution with 10 ml a gal.Thanks!!!
 
KonopCh

KonopCh

Well-Known Member
If product has 6% potassium silicate, how much K does it has?
@Castel

@ruwtz how far you go with K in coco? If I count everything except potassium silicate I am at 250.
 
Wastei

Wastei

Well-Known Member
Castel said:
I found 1 Kg of chemically pure Potassium Silicate (K2SiO3•nH2O) for under $10 from my chemical supply. It seems so many people are opting to rather purchase diluted solutions so I'm having trouble finding how much to add to my nutrient solution (Jacks 5-12-26).

The composition is:
K20 - 47-51%
K2O/SiO2 ratio 1.57 +/- 0.08

So trying to implement this in Hydrobuddy, I'm entering 49% as K20 and 31% as Si (given the 1.57 ratio of K2O to SiO2). I'm not sure if this is the correct way to enter it?

Anyhow, the only other person I have seen posting about adding pure Potassium Silicate was adding it to a Jacks 321 variation at 0.25g per gallon. This seems very low to me, and based on Hydrobuddy using the values above, at 0.25g per gallon provides the following PPMs:

K 8.059
Si 6.184

Jacks is already quite high in K, although I don't know at which PPM level K becomes toxic. Apparently it's nearly impossible to overdose Si however?

Anyone able to check my math? What would be a good target for Si PPMs in solution for coco?
Click to expand...
Use an EC/ppm meter like the rest of us! 100g in 1L is 10% strength. Very basic calculation. Aim for 30-50ppm.

Protekt is 10% strength with 8.7% Si if I remember that correctly.
 
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