Dear John,

Many thanks.  Several people have asked
the same question...

> Is that real gold leaf gilding?

Yes, it is real gold leaf.  The nodus and
nodus support are made of brass but they
are gilded with gold leaf in the same way
as the sun, and the Babylonian Hour-Lines,
and associated numbers.

I wanted to try gold-plate for the nodus
and nodus support but the advice given was
that it is impossible (or at least very
difficult) to gold-plate brass.  Next time
I shall use stainless steel which seems to
be much easier to plate with gold.

[Aside: the explanation about gold-plating
brass being difficult is that the zinc
content of brass interferes with the plating
process.  I am not wholly convinced because
you can have brass-plate easily enough!]

> I sure wish we could get nice big slate
> slabs like that here!

There are still some good slate quarries in
the U.K.  The noted ones are in Cornwall, in
Wales and in the Lake District (NW England).

[Aside: there is also good slate in Spain
and in Belgium if you look hard!]

Slate is quite a common building material
here, especially for roofing but also for
kitchen floors and worktops.

One problem with slate is that it is prone
to contain Iron Pyrites (fools' gold) which
looks quite nice when the slate is newly
honed but, outdoors, it quite quickly turns
to rust and discolours the whole slate.

For plaques and sundials, one has to specify
"monumental" quality slate.

The Selwyn slate came from the Lake District
and is in the form of a true ellipse whose
major axis is 1065mm (42") and minor axis
is 865mm (34").  The thickness of the slate
is 35mm (1.4").

This means that the slate weighs about 71kg
(156lb) which is quite heavy!  If you picked
up such a slab of slate on your next trip
over here it would probably go over the
weight limit of your hand-luggage :-)

We all wore steel-capped boots and were very
careful during the lifting!

The nodus wasn't attached to the slate until
almost the last moment.  There are three long
bolts through a brass base-plate on the back
of the slate.  This wasn't gilded.

The guy who attached the nodus wore surgical
gloves.  We don't like finger marks on gold
leaf!

All the best

Frank

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