What salts or minerals leach out of charcoal when it is soaked in water?
Charcoal
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I use both fine and medium charcoal in my mixes. I repot generally every two years, sometimes 3 years. It is just my feeling that charcoal ‘sweetens the mix’. I have never given a thought about it absorbing salts.
Plus I never use it again. It is all thrown away.
I do not fertilize with every watering. 2 with fertilizer, a 3rd watering with plain water.
Plus I never use it again. It is all thrown away.
I do not fertilize with every watering. 2 with fertilizer, a 3rd watering with plain water.
My question is not what charcoal absorbs but rather what leaches out of it. To raise both the pH and the ppm of the water solution it socks in.
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Charcoal is made from charred wood right? Wood is organic. So what could possibly be in charcoal to leach out? If the source wood is good, I think that the charcoal wood be as well.
The bark I use is from Douglas Fir. I know the some people would not use bark from pine trees. People feel pine bark holds too much sap or resin. I am told that resin is not good for orchid roots.
The bark I use is from Douglas Fir. I know the some people would not use bark from pine trees. People feel pine bark holds too much sap or resin. I am told that resin is not good for orchid roots.
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Ray will know.
He is our resident icon regarding questions like this.
I am an old timer when it comes to growing orchids. I like to keep things pretty simple. I honestly never thought to treat horticultural charcoal.
He is our resident icon regarding questions like this.
I am an old timer when it comes to growing orchids. I like to keep things pretty simple. I honestly never thought to treat horticultural charcoal.
Wood ash? This would be any salts present in original wood such as P, K, Mg, CA etc.... But bare in mind that charged organic molecules would also show up as "ppm" if you are using a conductivity meter to estimate tds. So any partially oxidized amino acids etc... Will also leach out and add to the tds.
Wood ash is very caustic and explains the high ph. If you run out of soap to wash your hands you can just dust yourself with wood ash and add a little water. It will turn the oils of your skin into soap!
Wood ash is very caustic and explains the high ph. If you run out of soap to wash your hands you can just dust yourself with wood ash and add a little water. It will turn the oils of your skin into soap!
Ray will not-, and does not know. I think Tyrone has the best response.
Ooooooh! Third person reference!! 
wash it and then place in distilled water and re-measure.
I did. Washed, rinsed, soaked rinsed in RO water. Then tested.
sorry, i meant tested in distilled water after 24hrs (no fertiliser)
Curious. I always hear “sweetens the mix” and sort of take it for granted. I add charcoal to all my mixes. I have seen people grow Vanda in pure charcoal chunks; not sure how that works but it seems to.
I'll have the result tomorrow.
That's what I always assumed. I have used it I mixed for ever. Never seen a problem with it. Now I tested it separately along with other elements I'm making mix with to see how each might effect the result. The high EC of the charcoal is a big surprise.
It may be irrelevant since the mix in pot of a growing plant never soaks overnight.
The high EC of that particular charcoal maybe a surprise, but that doesn’t mean they’re all like that.
A few decades ago I did some digging into the “sweetening” thing, and there were two general schools-of-thought.
One was the absorption of residues and the other was related to the very slow breakdown of the stuff in media that would otherwise decompose quickly. It’s probably a combination of the two, but we shouldn’t forget that up until commercially produced media were available, it was common to make it yourself out of coarse grit, twigs and leaves collected in nearby forests.
Back before I shifted my thinking to growing more wet than dry, I discontinued using the stuff because it seemed to build up minerals faster than other components, although I’ll admit that was likely a poorly-interpreted observation, as the other stuff was decomposin.
Whenever I have heard people talk about charcoal "sweetening" the mix it has been in the context of medium acidification so for me the alkaline charcoal makes perfect sense.
I think an interesting experiment would be to rinse the charcoal first and then put it in the water and measure what the conductivity and pH is. I think if you wash everything well whether or not charcoal is very alkaline becomes irrelevant.
I think an interesting experiment would be to rinse the charcoal first and then put it in the water and measure what the conductivity and pH is. I think if you wash everything well whether or not charcoal is very alkaline becomes irrelevant.
After soaking rinsed charcoal for 24 hours in distilled water the salts rose to 520 ppm. That's a gain of 516ppm above the 4 ppm water. The pH of soak water measures 9.0.
Just to be clear I'm not suggesting using charcoal is bad. I've always loved med to add it to organic mixes.
I've never given any thought to the concept of "sweetening" the mix, whatever that means. Actually I've considered it a positive carbon source for the roots to pickup.
Knowing that charcoal filters and absorbs toxins and metals makes me wonder if that is a good thing. Is it better to absorb the toxins and hold them forever in the root zone or allow them to leach on out with the flow through drain water?
I've never given any thought to the concept of "sweetening" the mix, whatever that means. Actually I've considered it a positive carbon source for the roots to pickup.
Knowing that charcoal filters and absorbs toxins and metals makes me wonder if that is a good thing. Is it better to absorb the toxins and hold them forever in the root zone or allow them to leach on out with the flow through drain water?
Charcoal filters by adsorption -- stuff just sticks to it. This adsorption will continue until it is full up with stuff. In aquariums we experience the problem of the carbon suddenly dumping all the stuff it has absorbed into the water column with little provocation hence the need to replace it regularly. For aquariums we could regenerate the carbon by putting it in boiling water.
Given Ray's observation that is "build up minerals faster than other components" I suppose there is a threat of it releasing all the stuff it has absorbed suddenly or the fertilizer components forcing all the bad stuff back into the medium.
Given Ray's observation that is "build up minerals faster than other components" I suppose there is a threat of it releasing all the stuff it has absorbed suddenly or the fertilizer components forcing all the bad stuff back into the medium.
