Back to Ganoksin | FAQ | Contact

Is it possible to induce porosity?


#1

I would like to think that I have a fair knowledge of metallurgy, as
with working with metals you need to know how they perform when
worked with.

The question I have is. Is it possible to induce porosity to a piece
of metal while performing a simple sizing job on a ring?

I sized an 18 carat white gold ring up a couple of sizes, nearly a
year later the customer came back as the ring was cracking, and has
been told by another jeweller that the metal is porous because of my
work in sizing! This to my mind cannot be possible! Is not porosity
in metals induced during casting?

Any ideas would be greatly appreciated.
John


#2

Perhaps there is a chemist on Orchid who can put this in the context
of water porosity in general. Is there any stoney or metallic
material which has zero porosity?

My own specific interest is that I have taken up a little outdoor
masonry work as a retirement hobby and already I am contending with
frost-heaving problems. If the liquid water gets into the stones, it
expands when it turns to solid water. Then there is crystal pressure.
As crystals precipitate out in the water and grow they expand and can
turn rock into powder.

This region has had a major quake every 500 years plus volcanic
activity so all rocks have micro and macro fractures.

The answer to your questions about small ring stones, John, will I
expect have more general applicability on a macro scale.

I have never heard any jeweller say to avoid putting rings in water
but I see no reason in theory why the metal and stone of rings could
not absord water under some conditions.

I wonder this. If you take a typical ring plus stone and expanded
the drawing of atoms, molecules and spaces between 1,000x what will
you get? Would it look like what cave explorers see with networks of
caverns and crevaces and tunnels?


#3

John- 18 Karat white gold. Shudder. Depending on the alloy it can be
wonderful or just like coat hanger wire with pits.

Where is the porosity? All over or just where it was sized? I’ve seen
solder over heated and thusly porous, but only at the solder site.

Sizing a ring should not cause the entire ring to be porous. I’ve
sized untold thousands of white gold rings in my career. Never seen
it happen any where else but the seam.

Jo Haemer
timothywgreen.com


#4
I sized an 18 carat white gold ring up a couple of sizes, nearly a
year later the customer came back as the ring was cracking, and
has been told by another jeweller that the metal is porous because
of my work in sizing! This to my mind cannot be possible! Is not
porosity in metals induced during casting? 

You can induce porosity in the solder joint but not in the bulk
metal. If the bulk metal is porous it is because it was a bad
casting. That said there can be another reasons that a crack could
form in the bulk 18k white. Fire cracking or stress cracking. These
articles outline the underlying issues.


http://www.ganoksin.com/gnkurl/ep80ye
http://www.ganoksin.com/gnkurl/ep80yf

James Binnion
James Binnion Metal Arts


#5

The simple answer is no you can not introduce porosity into a ring
by sizingit. unless it is in the solder joint itself which can occur
if the seam is not a good fit and you Used a lot of solder to fill
the gap…

There is depending on how you sized it the possibility of creating
stress inthe ring if it is rolled up instead of cut and gold added
which could show up latter. Proper annealing solves this problem.
Hope this helps…