Chris Hogg wrote:

On Tue, 26 May 2015 16:02:15 +0100, Chris J Dixon
wrote:

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

Just be aware that builders plaster is not the same as it used to be
many years ago, when it was derived from mined gypsum. These days most
of it is the by-product of flue gas desulphurisation at big coal-fired
power stations, where the flue gases are scrubbed with lime. As the
lime is use up, the efficiency of the scrubbing process drops away,
and the spent lime, now mostly gypsum, is sold off for building use.
But it still contains a little residual lime, so whereas in the past,
gypsum could be used around lime-hating ericaceous plants such as
rhododendrons, camellias and heathers to improve and even acidify the
soil (pure gypsum being mildly acidic), it would not be a good idea
these days.

Still OK as a 'clay-breaker' though.

I take your point. As it happens, I live in an area that features
both methods of production, and have even seen it being mined.
However, which one makes it into the local shops is anybody's
guess.

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.