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Work hardening silver


#1

My understanding is that thorough sandblasting will work-hardening
sterling silver. How does this compare to the level of work-hardening
created through tumbling?

Nancy


#2

Work-hardening depends on the metal getting deformed in some way. If
your steel-shot tumbling hammers the surface enough to deform it
microscopocally, then that part of the workpiece that’s been
deformed will be work hardened.

Unless some minute movement happens to the rest of the workpiece…
but then it’d be work-hardened minutely, I guess.

Brian

Auckland
New Zealand
www.adam.co.nz


#3
My understanding is that thorough sandblasting will work-hardening
sterling silver. How does this compare to the level of
work-hardening created through tumbling? 

Fairly similar, I think. But be aware that sand or bead blasting
with enough force and duration to give significant work hardening
also often causes significant distortion. I used this to advantage
years ago, in creating pieces with surfaces that needed to look torn,
distorted, warped, etc. I’d start with flat or lightly formed shapes
in 22 guage sheet silver. Controlling the bead blaster would cause a
whole lot more distortion than I expected before trying the method.
One can literally reshape the metal with the distortion caused by
stretching one side of the metal and not the other. Tumbling,
because it tends to be more uniform over all surfaces, and tends to
be a little gentler (which is why it takes longer) does not cause as
much distortion.

Like tumbling, bead blasting or sandblasting causes work hardening
pretty much only in the thin surface layer where distortion and
movement of the metal is taking place. In thin sheet, this can be
effectively much of the thickness of the metal. In heavier pieces,
it’s more a surface only hardening.

Peter Rowe


#4

Hi Nancy,

My understanding is that thorough sandblasting will work-hardening
sterling silver. How does this compare to the level of
work-hardening created through tumbling? 

While it’s true that tumbling sterling, but my guess would be that
will work harden it a little, the harden part of the item is very
shallow, shall we say,‘skin deep’. I haven’t tried sand or bead
blasting an item to harden it. I’d suspect sand/bead blasting would
only harden about the same.

Then, if you wanted a polished surface, you’d remove the hardened
portion in the polishing process.

Dave


#5
My understanding is that thorough sandblasting will work-hardening
sterling silver. How does this compare to the level of work-
hardening created through tumbling?

Blasting with glass beads or steel shot will do some surface
hardening, sand on the other hand will not do as much as it cuts the
surface rather than hammering it. The amount of hardening is going
to depend on how much air pressure and the mass of the bead or shot.
The greater the speed and mass the more deformation and the greater
the hardening. As to whether it is greater than tumbling it will
depend but in my experience in my shop it tends to be somewhat
greater than tumbling in stainless shot.

James Binnion
James Binnion Metal Arts


#6

I was rather sceptical about the ability of sand-blasting to work
harden metal, until I had an accident with a grill pan.

The enamelled grill pan assembly contains an aluminium insert and a
steel grill. The insert is a simple pressing made from 0.6mm (23
SWG) aluminium sheet. The pressing is just to create some
corrugations to add rigidity.

The grill is in the top oven and the accident occurred when I turned
the wrong oven to maximum and left it like that for an hour or so.
The insert was badly discoloured, and amazingly soft. The oven did a
really good job of annealing the aluminium.

I tried to abrade the discolouration, to no effect; the aluminium
was so soft that it simply distorted as soon as I applied any finger
pressure. I was unable to buy a new insert so, in desperation,
decided to use aggressive sand-blasting to remove the staining, and
just put up with the softness.

The sand-blasting removed the staining very effectively, but, to my
great surprise, also restored the original stiffness. The surface
was left as a matt finish.

Regards, Gary Wooding


#7

Hi Peter

How do you recover precious metals from this method?

Simone