Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On 07/06/10 08:57, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris

No reason whatsoever.

Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

On Jun 7, 8:57*am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Assorted rottable garbage also improves soils, so if you dig it up to
add gypsum, you could add rubbish under the surface too. Unused
plaster will bind the soil, used lumps wont.


NT

"Chris J Dixon" wrote in message
...
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

R.

On 7 June, 09:31, NT wrote:

Unused plaster will bind the soil, used lumps wont.

Run it through a cement mixer and a couple of rocks as a ball mill. So
long as you crunch it down enough to go through a sieve, it's fine.
Even just soaking it in an excess of water would be enough (this is
plaster, not cement).

I wouldn't add "rottable garbage" to soil either, it's much better to
rot this down separately. Otherwise you'll be short of nitrogen and
lawns in particular would suffer badly.

In article ,
Tim Watts writes:
On 07/06/10 08:57, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

No reason whatsoever.

Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

Yes - where about in the country are you?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

Hmm. I know it is, but I am scptical.

Our clay overlies enough chalk, and though it helps, it does make the
soil excessively alkaline.

We have found copius additions of orgamic material - peats, topsoils and
manures - and sand, to be a better bet.

Its back breaking work as well. Hire a rotovator or small digger to
break it up and mix it in.





http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?


As previous poster says, none really, except it sets hard and can make a
mess of drainage in a particular area. The same is probably true of pure
gypsum.

I've got areas of lawn that I simply left cement and plaster tailings
under and heaps of builders sand, They don't fare well.

The easy way of of making flower gardens in clay, is mulch. That will
decompose into decent topsoil, and you can pull annual weeds out of it.
Wood or coca shell. Or peaty compost.

Or if its for vegetables, cheat: We made raised beds and filled them
with gravel sand and topsoil. After breaking up the underlying clay pan
just a little.



Chris

Andrew Gabriel wrote:

In article ,
Tim Watts writes:


Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

Yes - where about in the country are you?

See sig. Ironically, in a village whose major industry is
plasterboard ;-)

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On 07/06/10 12:12, Chris J Dixon wrote:
Andrew Gabriel wrote:

In ,
Tim writes:


Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

Yes - where about in the country are you?

See sig. Ironically, in a village whose major industry is
plasterboard ;-)

Chris

I've got one of the gypsum mines and processing facilities round the
corner from me too. Ironically the dump bang over the road is unable to
accept plasterboard for recycling(!)

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

On Jun 7, 12:49 pm, Tim Watts wrote:
On 07/06/10 12:12, Chris J Dixon wrote:

Andrew Gabriel wrote:

In ,
Tim writes:

Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

Yes - where about in the country are you?

See sig. Ironically, in a village whose major industry is
plasterboard ;-)

Chris

I've got one of the gypsum mines and processing facilities round the
corner from me too. Ironically the dump bang over the road is unable to
accept plasterboard for recycling(!)

could that be addressed by the fabled "joined up thinking" we are all
looking forward to?

(IOW can you recycle old pb into new pb?)

Jim K

On 07/06/10 13:12, Jim K wrote:
On Jun 7, 12:49 pm, Tim wrote:
On 07/06/10 12:12, Chris J Dixon wrote:

Andrew Gabriel wrote:

In ,
Tim writes:

Even better, if you can find a source of lumpy out of date plaster for
free (try asking around).

Yes - where about in the country are you?

See sig. Ironically, in a village whose major industry is
plasterboard ;-)

Chris

I've got one of the gypsum mines and processing facilities round the
corner from me too. Ironically the dump bang over the road is unable to
accept plasterboard for recycling(!)

could that be addressed by the fabled "joined up thinking" we are all
looking forward to?

(IOW can you recycle old pb into new pb?)

Jim K

I must admit - I don't know if British Gypsum do recycling at the
Mountfield/Robertsbridge plant. Though if they can take crap out the
ground and turn it into plaster (they do all that here) I would have
thought they would have added a preprocessing feed for doing whatever
you need to old PB and sticking the result of it in with the raw
materials from the mine.

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Ragnar wrote:

"Chris J Dixon" wrote in message
.. .
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

"Chris J Dixon" wrote in message
...
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.


Interesting how gypsum comes out of nasty thick clay pits, yet we put it
back in as a clay improver?

S

Chris J Dixon wrote:
Ragnar wrote:
"Chris J Dixon" wrote in message
...
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.


If that's true, its news to me..

pretty sure that vinegar dripped on plasterboard fizzes..

Chris

Chris J Dixon wrote:
Ragnar wrote:
"Chris J Dixon" wrote in message
...
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.

Chris
I just checked, and its main constituent, calcium sulphate dihydrate is
mildly alkaline. giving a typical PH of about 7.4


If its the raw plaster of paris, its even more alkaline at a ph of 11+

In article ,
The Natural Philosopher wrote:
Chris J Dixon wrote:
Ragnar wrote:

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.

If that's true, its news to me..

pretty sure that vinegar dripped on plasterboard fizzes..

This is a TBE and a FQM (Totally Baffling Effect and Frequently Quoted
Misunderstanding). You are chemically correct, but biochemically
incorrect.

It isn't helped by the fact that the terms "acid soil" and "alkaline
soil" are so misleading - which is the TBE. The reasons that those
plants dislike lime has nothing to do with the acidity, but the fact
that they have difficulty absorbing iron, and calcium interferes
with one common form of plant's lime absorption. Sorry, I don't
know the details. Magnesium doesn't have the same effect, for
arcane chemical reasons, that I don't understand, either.


Regards,
Nick Maclaren.

wrote:
In article ,
The Natural Philosopher wrote:
Chris J Dixon wrote:
Ragnar wrote:

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.
If that's true, its news to me..

pretty sure that vinegar dripped on plasterboard fizzes..

This is a TBE and a FQM (Totally Baffling Effect and Frequently Quoted
Misunderstanding). You are chemically correct, but biochemically
incorrect.

It isn't helped by the fact that the terms "acid soil" and "alkaline
soil" are so misleading - which is the TBE. The reasons that those
plants dislike lime has nothing to do with the acidity, but the fact
that they have difficulty absorbing iron, and calcium interferes
with one common form of plant's lime absorption. Sorry, I don't
know the details. Magnesium doesn't have the same effect, for
arcane chemical reasons, that I don't understand, either.



Now it makes a little more sense..


Regards,
Nick Maclaren.

On Jun 7, 10:34*am, Andy Dingley wrote:
On 7 June, 09:31, NT wrote:

Unused plaster will bind the soil, used lumps wont.

Run it through a cement mixer and a couple of rocks as a ball mill. So
long as you crunch it down enough to go through a sieve, it's fine.
Even just soaking it in an excess of water would be enough (this is
plaster, not cement).

I wouldn't add "rottable garbage" to soil either, it's much better to
rot this down separately. Otherwise you'll be short of nitrogen and
lawns in particular would suffer badly.

So they say, but I've not seen this happen in practice. If you added
wood shavings or plenty of paper I daresay it would.


NT

On Jun 7, 8:57*am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Building plaster has other stuff in it besides gypsum, anyone know
what those additives are?


NT

"Chris J Dixon" wrote
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly £5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...er-p-6321.html

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under £5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris, if you can find a Farmers Shop (not a Farm Shop) they may well sell
Agricultural Gypsum in 25kg bags, which is what I bought. Mine was old
stock, a bit lumpy, and I paid £5. each.

--
Regards
Bob Hobden
W.of London. UK

NT wrote:
On Jun 7, 10:34 am, Andy Dingley wrote:
On 7 June, 09:31, NT wrote:

Unused plaster will bind the soil, used lumps wont.
Run it through a cement mixer and a couple of rocks as a ball mill. So
long as you crunch it down enough to go through a sieve, it's fine.
Even just soaking it in an excess of water would be enough (this is
plaster, not cement).

I wouldn't add "rottable garbage" to soil either, it's much better to
rot this down separately. Otherwise you'll be short of nitrogen and
lawns in particular would suffer badly.

So they say, but I've not seen this happen in practice. If you added
wood shavings or plenty of paper I daresay it would.


worms will take care of reducing grass clippings to compost!

But in general, yes. 3 years and then apply compost. You can hurry it
along, but why bother?

Gardening is a long term investment.

NT

"Tim Watts" wrote

I must admit - I don't know if British Gypsum do recycling at the
Mountfield/Robertsbridge plant. Though if they can take crap out the
ground and turn it into plaster (they do all that here) I would have
thought they would have added a preprocessing feed for doing whatever you
need to old PB and sticking the result of it in with the raw materials
from the mine.

British Gypsum make cat litter too, Nature Cat Gold, so that is probably
also gypsum and it's in granules too. Should be available at any good pet
place or could be ordered, but check the price first. Worth ringing BG first
to find out if it is pure gypsum.

--
Regards
Bob Hobden
W.of London. UK

NT wrote:
On Jun 7, 8:57 am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Building plaster has other stuff in it besides gypsum, anyone know
what those additives are?


filler mainly. Mica and so on. that's yer carlite bonding anyway.

The finishing plaster is almost pure gypsum IIRC.



NT

The Natural Philosopher wrote:
NT wrote:
On Jun 7, 8:57 am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Building plaster has other stuff in it besides gypsum, anyone know
what those additives are?


filler mainly. Mica and so on. that's yer carlite bonding anyway.

The finishing plaster is almost pure gypsum IIRC.



NT

AIUI gypsum is the raw mineral, which doesn't set when mixed with water.
It has to be hydrated to make plaster.

stuart noble wrote:
The Natural Philosopher wrote:
NT wrote:
On Jun 7, 8:57 am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....


On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Building plaster has other stuff in it besides gypsum, anyone know
what those additives are?


filler mainly. Mica and so on. that's yer carlite bonding anyway.

The finishing plaster is almost pure gypsum IIRC.



NT

AIUI gypsum is the raw mineral, which doesn't set when mixed with water.
It has to be hydrated to make plaster.

T'other way about. Gypsum is the hydrated stuff, which has to be
reducedd (de hydrated) to make plaster..then addition of water
rehydrates it, and it crystallises into solid chunks.

On Jun 7, 5:36*pm, The Natural Philosopher
wrote:
NT wrote:
On Jun 7, 10:34 am, Andy Dingley wrote:
On 7 June, 09:31, NT wrote:

Unused plaster will bind the soil, used lumps wont.
Run it through a cement mixer and a couple of rocks as a ball mill. So
long as you crunch it down enough to go through a sieve, it's fine.
Even just soaking it in an excess of water would be enough (this is
plaster, not cement).

I wouldn't add "rottable garbage" to soil either, it's much better to
rot this down separately. Otherwise you'll be short of nitrogen and
lawns in particular would suffer badly.

So they say, but I've not seen this happen in practice. If you added
wood shavings or plenty of paper I daresay it would.

worms will take care of reducing grass clippings to compost!

But in general, yes. 3 years and then apply compost. You can hurry it
along, but why bother?

Gardening is a long term investment.

NT

Vegetable garbage does wonders for the worm population, which produce
a fair bit of good poop. If there is such a thing.


NT

NT wrote:
On Jun 7, 5:36 pm, The Natural Philosopher
wrote:
NT wrote:
On Jun 7, 10:34 am, Andy Dingley wrote:
On 7 June, 09:31, NT wrote:
Unused plaster will bind the soil, used lumps wont.
Run it through a cement mixer and a couple of rocks as a ball mill. So
long as you crunch it down enough to go through a sieve, it's fine.
Even just soaking it in an excess of water would be enough (this is
plaster, not cement).
I wouldn't add "rottable garbage" to soil either, it's much better to
rot this down separately. Otherwise you'll be short of nitrogen and
lawns in particular would suffer badly.
So they say, but I've not seen this happen in practice. If you added
wood shavings or plenty of paper I daresay it would.
worms will take care of reducing grass clippings to compost!

But in general, yes. 3 years and then apply compost. You can hurry it
along, but why bother?

Gardening is a long term investment.

NT

Vegetable garbage does wonders for the worm population, which produce
a fair bit of good poop. If there is such a thing.



Interesting. We just compost ours.

takes a fair time to rot down, and the rats get a fair bit.


NT

Chris Hogg wrote:
On Mon, 7 Jun 2010 15:30:17 +0100 (BST), wrote:

In article ,
The Natural Philosopher wrote:
Chris J Dixon wrote:
Ragnar wrote:

I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.
If that's true, its news to me..

pretty sure that vinegar dripped on plasterboard fizzes..
This is a TBE and a FQM (Totally Baffling Effect and Frequently Quoted
Misunderstanding). You are chemically correct, but biochemically
incorrect.

It isn't helped by the fact that the terms "acid soil" and "alkaline
soil" are so misleading - which is the TBE. The reasons that those
plants dislike lime has nothing to do with the acidity, but the fact
that they have difficulty absorbing iron, and calcium interferes
with one common form of plant's lime absorption. Sorry, I don't
know the details. Magnesium doesn't have the same effect, for
arcane chemical reasons, that I don't understand, either.


Regards,
Nick Maclaren.

Many years ago, most gypsum was mined; a great deal of it came from
Belgium and northern France; hence the name Plaster of Paris. However,
the modern desulphurisation of flue gases from coal-fired power
stations, using a slurry of hydrated lime and ending up with a slurry
of (mostly) gypsum, has resulted in lots of cheap gypsum as a waste
by-product. This means that gypsum mining is no longer commercially
viable except for specialist application that can carry the cost. The
conversion of hydrated lime to calcium sulphate (gypsum) during the
desulphurisation process is not 100% efficient, simply because the
efficiency of sulphur oxide absorption drops off when there's not much
lime left in suspension, so it's not cost-effective to keep using the
lime slurry until it's 100% converted. After filtering and drying, the
residual lime in the gypsum reacts with carbon dioxide in the air to
give calcium carbonate (think: lime mortar). Hence most of the gypsum
currently available will fizz with dilute acid, and has an alkaline
pH. Pure gypsum doesn't fizz in this way, and naturally has an acid
pH.

The reason some plants dislike 'lime' has a great deal to do with soil
acidity. In this context, 'lime' actually means calcium carbonate
(chalk), rather than quicklime (calcium oxide) or hydrated lime
(calcium hydroxide), both of which convert fairly quickly in the soil
to calcium carbonate by reacting with carbon dioxide in the air.
'Limey' soils, i.e. chalky soils, typically have pH values of around 8
to 8.5. So-called lime-hating plants such as many of the ericaceae
have a greater requirement for iron (and possibly manganese), than
other plants. The solubility of iron and manganese in the soil
decreases significantly as the soil pH increases from say pH 6 to pH
8.5 (neutral is pH 7), a typical range of soil values. At the high pH,
there just isn't enough iron and manganese available in the soil to be
taken up by the plants to satisfy their needs, and yellowing of the
leaves (chlorosis) is the result. It has nothing to do with the
presence of calcium in the soil per se. Pure gypsum (not the modern
stuff from desulphurisation) used to be recommended as an additive to
heavy soils to open them up, where it was wanted to grow
rhododendrons, in place of 'lime' which has a similar effect on the
soil but is alkaline.

Thank you!

well written and increases understanding. Can't ask for more!


now to buy some of that manganese and iron feed for the 'ericaceous' tubs.

On 7 June, 21:06, Chris Hogg wrote:

This is a TBE and a FQM (Totally Baffling Effect and Frequently Quoted
Misunderstanding). *You are chemically correct, but biochemically
incorrect.

It isn't helped by the fact that the terms "acid soil" and "alkaline
soil" are so misleading - which is the TBE. *The reasons that those
plants dislike lime has nothing to do with the acidity, but the fact
that they have difficulty absorbing iron, and calcium interferes
with one common form of plant's lime absorption. *Sorry, I don't
know the details. *Magnesium doesn't have the same effect, for
arcane chemical reasons, that I don't understand, either.

Regards,
Nick Maclaren.

No quote chopping, so that it hits the archive fully.

So what's the stuff from the graden centres? Pure gypsum rather than
FGDS, so as to avoid the alkalinity change?

Many years ago, most gypsum was mined; a great deal of it came from
Belgium and northern France; hence the name Plaster of Paris. However,
the modern desulphurisation of flue gases from coal-fired power
stations, using a slurry of hydrated lime and ending up with a slurry
of (mostly) gypsum, has resulted in lots of cheap gypsum as a waste
by-product. This means that gypsum mining is no longer commercially
viable except for specialist application that can carry the cost. The
conversion of hydrated lime to calcium sulphate (gypsum) during the
desulphurisation process is not 100% efficient, simply because the
efficiency of sulphur oxide absorption drops off when there's not much
lime left in suspension, so it's not cost-effective to keep using the
lime slurry until it's 100% converted. After filtering and drying, the
residual lime in the gypsum reacts with carbon dioxide in the air to
give calcium carbonate (think: lime mortar). Hence most of the gypsum
currently available will fizz with dilute acid, and has an alkaline
pH. Pure gypsum doesn't fizz in this way, and naturally has an acid
pH.

The reason some plants dislike 'lime' has a great deal to do with soil
acidity. In this context, 'lime' actually means calcium carbonate
(chalk), rather than quicklime (calcium oxide) or hydrated lime
(calcium hydroxide), both of which convert fairly quickly in the soil
to calcium carbonate by reacting with carbon dioxide in the air.
'Limey' soils, i.e. chalky soils, typically have pH values of around 8
to 8.5. So-called lime-hating plants such as many of the ericaceae
have a greater requirement for iron (and possibly manganese), than
other plants. The solubility of iron and manganese in the soil
decreases significantly as the soil pH increases from say pH 6 to pH
8.5 (neutral is pH 7), a typical range of soil values. At the high pH,
there just isn't enough iron and manganese available in the soil to be
taken up by the plants to satisfy their needs, and yellowing of the
leaves (chlorosis) is the result. It has nothing to do with the
presence of calcium in the soil per se. Pure gypsum (not the modern
stuff from desulphurisation) used to be recommended as an additive to
heavy soils to open them up, where it was wanted to grow
rhododendrons, in place of 'lime' which has a similar effect on the
soil but is alkaline.

Bob Hobden wrote:
"Tim Watts" wrote

I must admit - I don't know if British Gypsum do recycling at the
Mountfield/Robertsbridge plant. Though if they can take crap out the
ground and turn it into plaster (they do all that here) I would have
thought they would have added a preprocessing feed for doing
whatever you need to old PB and sticking the result of it in with
the raw materials from the mine.

British Gypsum make cat litter too, Nature Cat Gold, so that is
probably also gypsum and it's in granules too. Should be available at
any good pet place or could be ordered, but check the price first.
Worth ringing BG first to find out if it is pure gypsum.

No, that's made from bentonite clay, which is the most absorbent, clumpy
dirt the Earth can offer.


Ian

The Natural Philosopher wrote:
stuart noble wrote:
The Natural Philosopher wrote:
NT wrote:
On Jun 7, 8:57 am, Chris J Dixon wrote:
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....


On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris


Building plaster has other stuff in it besides gypsum, anyone know
what those additives are?


filler mainly. Mica and so on. that's yer carlite bonding anyway.

The finishing plaster is almost pure gypsum IIRC.



NT

AIUI gypsum is the raw mineral, which doesn't set when mixed with
water. It has to be hydrated to make plaster.

T'other way about. Gypsum is the hydrated stuff, which has to be
reducedd (de hydrated) to make plaster..then addition of water
rehydrates it, and it crystallises into solid chunks.


Ah, right! But gypsum, as in agricultural gypsum, presumably doesn't set
then? Not that it makes much difference when it's mixed with soil.

I'd think about vermiculite as a conditioner. Okay, you have to break
the clay up to incorporate it (which probably does more to improve it
than any additives), but it aerates the soil permanently and doesn't
break down into anything else. Just don't buy the agricultural grade,
which is rather over-priced.

Chris Hogg wrote:
On Mon, 7 Jun 2010 15:59:26 -0700 (PDT), Andy Dingley
wrote:


So what's the stuff from the graden centres? Pure gypsum rather than
FGDS, so as to avoid the alkalinity change?

I've never bought any, so I can't comment, but my guess would be the
latter. A simple pH test would tell you.

there would be no reason to supply anything other than the dihydrate for
any purpose other than actually making plaster.

Its costlier and has shorter shelf life.

In article CNoPn.29680$hP7.6557@hurricane,
stuart noble writes:

Ah, right! But gypsum, as in agricultural gypsum, presumably doesn't set
then? Not that it makes much difference when it's mixed with soil.

Building gypsum sets initially when you dump it outside, but as
it's slightly soluable anyway (which is why damp eventually destroys
plasterwork), it quickly crumbles apart again when kept wet, and
plants have no problems pushing roots through it. Grass seems to
love growing on it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 08/06/10 16:00, Andrew Gabriel wrote:
In articleCNoPn.29680$hP7.6557@hurricane,
stuart writes:

Ah, right! But gypsum, as in agricultural gypsum, presumably doesn't set
then? Not that it makes much difference when it's mixed with soil.

Building gypsum sets initially when you dump it outside, but as
it's slightly soluable anyway (which is why damp eventually destroys
plasterwork), it quickly crumbles apart again when kept wet, and
plants have no problems pushing roots through it. Grass seems to
love growing on it.


Yes indeed. The bit of my lawn used last year for dumping plaster
washings (from mixing) is fine. In fact the grit from the coal ash
bucket seems to be upsetting it more.

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

On Jun 7, 1:46*pm, Chris J Dixon wrote:
Ragnar wrote:

"Chris J Dixon" wrote in message
.. .
Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly 5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321.....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under 5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?
I don't really know the answer to your question, but I would warn you not to
use gypsum if you want lime-hating plants such as heathers, rhododendrons
etc

Other sources seem to be of the opinion that one of the benefits
of using gypsum is that it is essentially neutral, and will not
alter pH.

Gypsum is calcium sulphate which is more or less neutral but is
calcium rich which will hurt alpines. Nothing seems to hurt
rosydandelions.

Sand is neutral and acid. Use a mix of sand and gypsum with sawdust or
shedded organic stuff. Grow lupins for a while. Any nitrogen loss will
soon come back.

Sand and clay = loam. I think sand and gypsum = marl.

AJH wrote:
On Mon, 07 Jun 2010 21:06:14 +0100, Chris Hogg wrote:

Gypsum is the fully hydrated form (di-hydrate, CaSO4.2H2O). There are
several types of plaster, but the common one is the hemi-hydrate
(CaSO4.½H2O), made by heating gypsum to around 125°C, when it loses
water. On suspending in water, this reverts to the di-hydrate and
sets.

Does this mean I can re vitalise old multifinish by heating it to
125C?


I thought it was a bit hotter than that..

and it will bneed re grinding in a ball mill or similar, but yes, in
principle..


I've just had to recycle 980kg of plaster materials (at a cost of 65
quid plus delivery) which I suspect is about 30% of what the builders
purchased. I've gone right off dot and dabbed plasterboarding as a
result even given the time saving. Conventional plaster also is easier
to fix to.

AJH

On 7 June, 14:48, "spamlet" wrote:
"Chris J Dixon" wrote in messagenews:009p061f4aaf3f8kut728pv6q66ataa0fp@4ax .com...





Having just extended a flower bed to incorporate what has been
lawn for 40 years, I am left with some pretty solid clay soil.

Gypsum is recommended as a soil improver, but appears to be sold
in garden centres as a proprietary product costing nearly �5 for
2.5 kg.

http://www.capitalgardens.co.uk/clay...itioner-p-6321....

On the other hand, I can pick up a 25 kg bag of multi-finish
plaster for under �5, and AFAIK this is essentially the same
material.

Any reasons not to go with plaster?

Chris
--
Chris J Dixon �Nottingham UK


Have dancing shoes, will ceilidh.

Interesting how gypsum comes out of nasty thick clay pits, yet we put it
back in as a clay improver?

S- Hide quoted text -

- Show quoted text -

Most gypsum come from scrubbers fitted to coal burning power
stations. The sulphur dioxide converts limestone to calcium
sulphate. The best permanent clay improver is "sharp" sand. The
difficult bit is mixing it thoroughly with the clay. Even a
rotovator is not very good as it only churns up the top layer. It's
taken me three years to get it mixed with hand digging but the results
are good. Compost is the way to go too.
Get yourself a shredder if you have a big hedge. If you know a
landscape gardener, you get get truck loads of shreddings off them for
free. They compost down very quickly if there's lots of leaf. ie
Summer time is the best.