Have stripped many layers of paint off a victorian cast iron knocker.
A very fine, intricate casting has emerged. Leaves, flowers etc. Am
back to bare metal except that the surface remains oxidised.
Rust-coloured. Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?

Jim

On 3 May 2005 03:07:09 -0700, (jim) wrote:

Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Electrolysis. Search this ng, rec.woodworking, or the web. It's dead
easy and gives good results.

You'll never get cast iron to be "shiny", as the material is too
inhomogeneous to really take a polish. Generally a dull grey is the best
you can achieve.

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion?

Personally I'd use a black bituminious paint, either truck chassis paint
thinned down a bit, or "Black Jack" bitumen primer from Screwfix (dead
handy stuff). The Victorians would have finished it in black. Possibly
red or dark green, and maybe even coachlined in cream or gold leaf, but
not usually for door furniture.

Andy Dingley wrote:

You'll never get cast iron to be "shiny", as the material is too
inhomogeneous to really take a polish.

How come the Gallery (and other) selection of reproduction cast iron
fireplaces have polished shiny silver details?

Hi Jim
Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Don't think you will ever get it shiny, but thats not how it would have
looked originally anyway. Have it bead blasted, like shotblasting but with
glass beads. Or shotblasting with a fine grit.

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?

I'd go for black like Andy said. Hamerite Smooth?

Dave

"jim" wrote in message
m...
Have stripped many layers of paint off a victorian cast iron knocker.
A very fine, intricate casting has emerged. Leaves, flowers etc. Am
back to bare metal except that the surface remains oxidised.
Rust-coloured. Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?

Many ages ago people shined up their cast iron grates with stuff called Zube
which was a graphite based polish in a lead toothpaste type tube and you got
a special brush from Woolworths, bit like a shoe brush, to put it on with .
I don't think this is still on the market but it was very effective.


rusty

Rusty wrote:
Many ages ago people shined up their cast iron grates with stuff called Zube
which was a graphite based polish in a lead toothpaste type tube and you got
a special brush from Woolworths, bit like a shoe brush, to put it on with .
I don't think this is still on the market but it was very effective.

Zebo, or Zebrite, I think. Still around locally; but I'd go for the
painting option. I'm sure the Victorians wouldn't have used it on their
door knockers!

David

On Tue, 3 May 2005 13:34:34 +0100, "Rusty"
wrote:

Many ages ago people shined up their cast iron grates with stuff called Zube
which was a graphite based polish in a lead toothpaste type tube

Zebo - still common today. It's a black colour, but it's not a polish.
The graphite is in oil so it's pretty much impossible to shine it (it
also wipes off on your fingers). If you want a shine, find a _wax_ with
graphite in it. Neither of these would protect against outdoor rust
though.


--
Cats have nine lives, which is why they rarely post to Usenet.

Rusty wrote:

"jim" wrote in message
m...

Have stripped many layers of paint off a victorian cast iron knocker.
A very fine, intricate casting has emerged. Leaves, flowers etc. Am
back to bare metal except that the surface remains oxidised.
Rust-coloured. Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?


Many ages ago people shined up their cast iron grates with stuff called Zube
which was a graphite based polish in a lead toothpaste type tube and you got
a special brush from Woolworths, bit like a shoe brush, to put it on with .
I don't think this is still on the market but it was very effective.


think its still around...

rusty

"Rusty" wrote in message
...

snip

Many ages ago people shined up their cast iron grates with stuff
called Zube

uselessinfo

Zubes were cough sweets made by F W Hampshire's in Derby, sold with the
catchy slogan: "Go, suck a Zube!"

/uselessinfo


--
Kevin Poole
**Use current month and year to reply (e.g. )***
Car Transport by Tiltbed Trailer - based near Derby

jim wrote:
Have stripped many layers of paint off a victorian cast iron knocker.
A very fine, intricate casting has emerged. Leaves, flowers etc. Am
back to bare metal except that the surface remains oxidised.
Rust-coloured. Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Put the thing on a bonfire. Let the bonfire go out and the ash
cool until you can handle your knocker with your bare fingers.
Go over it with a wire brush, the sort with a wooden handle
and several rows of bristles, not a rotary one! Place the brush
on the metal and oscillate it, don't scrub in one direction
like a scrubbing brush. This will get all traces of paint and
rust off it.


Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?

I suppose you could varnish it, or go at it with some Zebo or
something, although you'd have to re-do the latter every so
orten. You won't be able to polish it bright-n-shiney-silver,
it will be grey. Hmm, yes, try blacking it, you can always
re-treat it if that doesn't work.

In message , jim
writes
Have stripped many layers of paint off a victorian cast iron knocker.
A very fine, intricate casting has emerged. Leaves, flowers etc. Am
back to bare metal except that the surface remains oxidised.
Rust-coloured. Would like to get back to shiny metal but the casting
is too intricate to do this by physical abrasive means, at least in
the nooks & crannies. Any suggestions, please?

Would it be possible to then apply a clear protective coat to allow
the knocker to survive exterior use without corrosion? Is there any
product that would do the job?

Would phosphoric acid be a good way of doing this ?


--
geoff

On Tue, 03 May 2005 20:22:53 GMT, raden wrote:

Would phosphoric acid be a good way of doing this ?

No. Phosphoric acid doesn't _remove_ rust - instead it converts it to a
more stable iron phosphide. You'll still leave the rough rusty surface
behind. Besides which, it doesn't work as well on cast iron as it does
on steel.

If you want an acid dip to clean it, you'd be better with citric acid,
or even hydrochloric.

In message , Andy Dingley
writes
On Tue, 03 May 2005 20:22:53 GMT, raden wrote:

Would phosphoric acid be a good way of doing this ?

No. Phosphoric acid doesn't _remove_ rust - instead it converts it to a
more stable iron phosphide. You'll still leave the rough rusty surface
behind. Besides which, it doesn't work as well on cast iron as it does
on steel.

But then he will have a good base surface to work from

--
geoff

On Wed, 04 May 2005 00:16:21 GMT, raden wrote:

But then he will have a good base surface to work from

No, he'll have a crap base surface to work from. It's cast iron - it
expands in volume when it rusts. You can try to stabilise it with
phosphoric, but this will have two drawbacks. First of all you lose
detail - for a decorative piece like a doorknocker, you really want to
avoid this. Secondly you can't stabilise rust on cast iron. Because of
this same volume expansion, the rust layer is insubstantial and
unstable, even when chemically treated.

Use the electrolysis. It works really well on CI.

Andy Dingley wrote:

It's cast iron - it expands in volume when it rusts.

The iron actually decreases in volume, surely.

Thanks to you all for your helpful advice.

Jim