"geraldthehamster" wrote in message
...
On 19 Aug, 16:02, "Spamlet" wrote:

Then, there's sandstone and sandstone. Do you know what sort it is or
where
it came from (geologically). It must be fairly tough if it has lasted from
mediaeval (nice to see the proper spelling) times, though shame the church
had to go.

I don't know the exact source; however, the church will have been in
or around York. It was demolished in the 19th century and the window
re-erected as a folly in a garden. It subsequently fell down and had
to be removed.

You might try a drop of acid on a piece of the stone and see if it fizzes.
This would indicate a limy matrix is holding it together, and you might be
able to 'weather' it with a mild acid spray to loosen some of the grains
and
then pressure wash them out (mind if it *is* very soft like the acidy
stuff
we do get round here, the pressure washer will drill right through it if
you
are not careful.).

Interesting ideas. I was going to have a go with the pressure washer
and see if it made any impression. The stone really is quite soft.

Mind you, if these blocks are two man jobbies and your wall is low, and
your
stone has nice flat faces, does it need mortar at all, other than as TNP
hints, to soften the stress of any subsidence? You could leave gaps for
plants, and/or drainage too.

Well, some are two-chap and others are one-chap. Not huge. The wall
will abut a pavement along which children walk to school, so I
wouldn't want anything falling off it!

Thanks
Richard

Interesting that you say the stone is soft, as traditionally the
'York'stones would be expected to be fairly hard as cemented with silica,
but it could vary from quarry to quarry, eg:
http://www.myersgroup.co.uk/jwqh/Env....asp?pageID=24

Ah, I miss my old school geology field trips!

S