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Testing suitability of sand and grit


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Yesterday I went to get some silica sand and decided against it as it looked too small a grain. I asked if they had any horticultural sand or grit and they said no. It was a local aggregate place. They didn't know what was in their products at all. I asked if they had anything coarser and was told "this here is what we call plastering sand and this one is what we call building sand". One was coarser than the other and, if inert, would be quite suitable. I got samples of both but have already ruled out one as it had too much dust in it.

How do I test this with my TDS meter and what increase in levels are deemed acceptable and what are not? Do I put it into a tray of rainwater and then monitor the TDS over a period of time? I don't know how long I should do it for etc.

It would be great to have this to use in outdoor situations as I'm sick of perlite washing everywhere and being generally too light. And this is half the price of perlite.

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plasterers sand and building sand is just normal bog standard sand. building sand has rounder grains and plasterers sand should have more jagged grains. The dust would just be smaller particles of the sand and so if the sand is ok then the dust will not be a problem.

To test I would put sand in distilled or rain water, shake vigorously, let stand for a few days, the longer the betterto give anything in the sand a chance to dissolve into the water. filter of the sand to remove all particulates. you could use one of those paper coffee filters if you dont have the proper gear. then test the water that has filtered through

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yes if you let the particles settle out as they may have an effect on the reading. But I would definately leave it a number of days if not longer because if you do use the sand it will be leaching out minerals over a long time period. The initial amount leached out as soon as you add the water might be small and therefore seem safe. Its how much leaches out over the long term that is of concern.

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You can test whether it has any lime in with some acid. Add acid and it will fizz if there is any lime, I use citric acid powder and boiling water, which I normally use for descaling the kettle. If it does not have any lime then it would be worth trying, wash several times and pot up a few test plants.

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Lime free horticultural sharp sand is what you need.

Even that's not a guarantee. I've had 'lime free' horticultural sand that fizzed like crazy when I tested it with lactic acid.

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I didn't get on well with sand or gravel a couple of years ago when I experimented with it and my plants suffered especially over winter. The mix became heavy compressed and anaerobic compared to peat/perlite so I opted for large coarse grade perlite and I am very happy with it and so are the plants.

I also found so called lime free sand to fizz and contain lime when testing it.

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sharp sand should be coarser than building sand or plastering sand from the builders merchant,think they normally come from the same quarry but the sharp sand has the fine grains washed out of it and is used for screeding or mixed with gravel for concrete,building sand for brick work and plastering sand for render ,so if i were you i would test some of their sharp sand as it should have the larger grains

Edited by corky
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Spoonful of sand in a bowl, spoonful of citric acid. Add a splash of boiling water. Watch for the fizz!

Thanks for that mate. Sounds simple enough.

Maybe careful with that. I believe it is also an ingredient in making explosive substances by certain naughty people...

Not everyone over here is in the IRA you know. :bomb::sarcastic_hand:

I'm on very good terms with the pharmacist at the bottom of the road. I feel like Karen from Will & Grace, I have him on speed dial.

If there's a winemaking shop nearby, it's a very common ingredient for home wine making.

I noticed that it is used in brewing sometimes. I think there's a brew shop somewhere in Cork city. :cheers:

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Well I did the acid test on the sand and it fizzed like a mother and stunk the place out. I shall get a sample of their silica sand and truly see if it is too fine and if it is inert. Most people use silica sand so it's probably fine right?

I really hope I can sort this out as it's costing me a fortune in perlite. Sand is less than half the price.

Edited by Richard Bunn
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