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Ok guys, everyone don't panic!

I've just tested it!.....

Mixed with distilled malt vinegar...

c8xYt2szBX9Ja9NZvhQKiBn-Kp5X2BooBWiVEbjv

https://photos.app.goo.gl/CZKdg8ZPES7KhEpu2

Not a single bubble.

 

pH tested with Johnson Universal Indicator paper....

Just with ambient moisture already present in sand...

ZuyJQ-QGh6KpGuwlEMk7hgxYAuYY_EHDvGmhX17s

https://photos.app.goo.gl/nPhrOtjMA0CfRByg1

 

With RO water added to sand to free it up a bit...

xaLoTE_qkBZGbJN-DjMV0oCN_1IFM1JQWH3Dzzm4

https://photos.app.goo.gl/2dZMT0xuJk1HQr4b2

 

 

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Just rechecked the pH after a 24hr soak and a good stir - still coming up as pH 6.

As a control, I took a small piece of tufa and placed it in some of the same vinegar, and you could see it bubbling.

I hate to say it, but I think I like this sand better than the RHS sand. It looks really good, and seems to have less very fine particles.

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I repotted my VFT's in a mix of the RHS sharp sand and Melcourt. One tray is not growing particularly well. Not sure if it the sharp sand or the Melcourt that is the problem. I might repot in the Spring with a brand of coir that I trust. 

I spoke to Mike King a week ago and he not sure about Melcourt for VFT's. Jury's out. 

Mike absolutely raves about Melcourt for Sarries though.

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1 hour ago, David Ahrens said:

I repotted my VFT's in a mix of the RHS sharp sand and Melcourt. One tray is not growing particularly well. Not sure if it the sharp sand or the Melcourt that is the problem. I might repot in the Spring with a brand of coir that I trust. 

I spoke to Mike King a week ago and he not sure about Melcourt for VFT's. Jury's out. 

Mike absolutely raves about Melcourt for Sarries though.

I also tried so VFT in a Melcort potting park and granite grit, and the growth was terrible compared to plants in a Peat/Perlite mix, so I also assume its the Melcourt.

Yet I have trialled some Disa Orchids in the same mix that Mike uses and have had a really good growth with it.

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If we're talking about VFTs, I read a fascinating article by someone who visited VFT habitat who said they grew on sand with a layer of organic matter overlaying it. So 12 months ago I planted mine in horticultural sand with 1 inch of moss peat on the top and they have done wonderfully. I reckon you can grow them in almost anything which is acid/neutral and has no dissolvable minerals. There was mention of them also growing in pine needles overlaying sand.

Edited by Karsty
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  • 2 weeks later...

Ok Folks, the controversy continues....

As a control, I took some Kelkay, RHS Gardeners Collection Horticultural Grit Sand, Washed "lime free" graded grit sand, and added sulphuric acid to it. Here is a video of it a few minutes later, after initially giving it a proper stir and getting all the ambient air bubbles thoroughly out...

https://photos.app.goo.gl/ilJ7sPhnj9E8jFD02

!

Edited by Karsty
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Wow! I got a phone call from Kelkay asking me if I would be kind enough to take the video off YouTube until they had completed their investigation.

I also just bought a new pack of their RHS Grit Sand to test that also. It is bubbling away!

And I've tested a bit more of the Daill sharp sand from B&Q, and it produces almost absolutely zero bubbles.

Edited by Karsty
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I’ve found their potting grit is fine so far, so it sounds like something has gone awry with the sand. 

I’ve only potted a few in the grit as part of some soil experiments, but if the supposed ‘good stuff’ can be tainted I won’t be using it when I repot the whole collection in future.

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  • 2 weeks later...
  • 1 month later...

Ok Folks, we have a result of sorts.

The Commercial Manager of Kelkay at last got the chance to get back to me a couple of days ago.

I was talking to her on the phone for half an hour! What she was explaining to me was, in a nutshell, the sand is regularly tested by outside agencies (testing houses), and she has double checked all of these, and she has double checked with the RHS officials who approve their sand. All of the results still come up as acceptable.

It seems that there is an allowable quantity of "lime" in a "lime-free" product. If I understood correctly, it is a maximum of 0.25%. She openly confesses not being a chemist, so she is not an expert in this exact subject, but that is it in a nutshell. She was a very encouraging person to deal with about this issue, she said she had found this process very interesting!

I will contact a testing house to find out how they test for this.

I asked her if she could send me an analysis of the sand, which I believe she is doing.

For us plant enthusiasts who regard things to the chemical level this still is a worrying result when we are without a full explanation of the chemistry involved. If we need to make an acid mix, we need to know exactly how it can remain acid enough when we include something that contains "lime". I also told her about the Diall sharp sand from B&Q, which bizarrely is the best sharp sand I have seen within living memory. It also only made the slightest trace of bubbles when tested with dilute sulphuric acid.

I would still like to find out what the chemistry is in this whole issue.

Is the "lime" in the sand pulverised sea shells? This would make it harder to dissolve? as it is contained within a protein matrix and would make it far less influential in the mix? Even if that was the case, I'd need to really know for a fact that it has no effect.

I said to her that we would appreciate it most if it stated on the packet what the sand really contains and/or what it might contain. She said she would put that forward to those concerned, but if she was to get a whole analysis itemised on the bags it would mean going through a whole new set of procedures and legislation and that is beyond their scope.

I feel like saying "The journey continues..."

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Hi, just been through this thread and taken a look at some of the comments and the photos. Interesting!

Now I've a bit of time I'll see if I can get some more definitive thoughts on what's been observed. Sand would have to be 100% silica sand to be 'perfect' nothing you buy on the street is. If you saw the price of pure silica sand you'd wince. However, the impurities don't have to be lime to react with acid and could be a range of other carbonates, silicates, etc. The lime (calcium salts) may well be within specification and acceptable.

I've used the RHS 'lime free' sand for years (note they do one lime free and one that isn't marked as lime free). Used other sands at times too but with all seen variability which probably shouldn't be a surprise. If any didn't look right or plants looked 'unhappy' used the sand elsewhere.

As this seems to come up every few years lets try to put to bed.  If anyone has a specification for lime free sand could they post? Likewise for any standard testing? I'll sample the bag I have this weekend and see what I can do with it next week. Watch this space!

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Hi Dunc, thanks for that.

It's too late at night now for me to fully focus on this, But I would really like to know what goes on with all this. Acids reacting with silicates to produce gas? Have you got the capability to test for more than just a gas-producing reaction? (I am just about getting it together to see if the gas puts out a flame). When a product specifies lime-free, well, that's what it should be right? It either is or isn't.

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I have contacted the testing house SOCOTEC. And I've contacted the RHS again asking for any details they can give me about the whole matter, things like how they test it, exactly what they test for, exactly what results do they get, how do they decide what is acceptable, etc., etc. I can't wait to find out all these details!

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  • 1 month later...

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