Filling porosity

Jewelry Discussion
1

Hi

I have a sterling silver ring I am looking to make the master copy
for a silicone mould.

Problem is there are a few porosity holes less than.8mm in diameter
that will need filling. Anyone got any tips or tricks before I make
a mess of it trying to fill it with easy solder?

Thanks

2

My first choice is to use a laser welder to weld the holes with the
proper filler wire. If the holes are that big, drill and fill with
wire and hard solder if you don’t have a laser welder.

Never use easy solder because when you finish the piece it will
polish out before you get it finished for molding. If you have
smaller holes that can be burnished over use an old setting bur
ground and polished into a square/round shape or triangle/round
shape, put it in your flex shaft and burnish over the porosity, go to
2/0 or 4/0 emery paper and lightly polish…

Best of Luck,
Russ Hyder

3

Dave,

Clean the porosity holes out with a round bur and make sure there is
no Investment or dirt in the hole.

Melt some small beads of sterling silver. Flow some solder on the
beads and then solder the beads into the holes.

For best results, hammer the bead and the surrounding area down ( If
you have a graverMax this works great for this ) and then file, sand
and lightly buff the piece.

Good luck
Greg DeMark

4

In Australia there is a two part epoxy putty called Milliput that is
very good at filling tiny cracks and sets really hard, you could try
that.

Anna Williams

5

The answer is “Porosity Killer”. This small inexpensive tool is a
rotary hammer that hammers and burnishes metal into small holes.
It’s available from The Contenti Co. in Rhode Island.

Ray Grossman

6

Dave,

Problem is there are a few porosity holes less than.8mm in
diameter that will need filling.

the problem usually encountered is that you can’t get the holes clean
down inside. If you can manage that, filling them is no big deal. I
usually take a bur and clean them out…sometimes even making them a
little larger. I then just pickle the piece real good, flux and
solder away. Apply as little flux as you can and dry it with heat
BEFORE adding the solder. If you can keep the flux in the cavern it
is best I think. Sometimes I find it helpful as well that if I can, I
begin the heating from underneath the pit. I use a titanium pick and
put the solder right down in the pit… not on top. Otherwise, the
solder wants to flow everywhere but DOWN in the pit… Kinetics at
their best. Make sure the solder is super clean too. Cleanliness here
though is the key to success!

Good Luck. Dan.
DeArmond Tool
http://www.classwax.com

7

Dave,

Problem is there are a few porosity holes less than.8mm in
diameter that will need filling. Anyone got any tips or tricks
before I make a mess of it trying to fill it with easy solder?

Try fusing Argentium (maybe a granule) onto the sterling. They fuse
together easily with a little flux. Argentium tends to slump a
little, so with luck you’ll have minimal cleanup.

Good luck.
Jamie

8

Before I had access to a laser, and even sometimes still, after
using a laser to fill in pitting in a casting, I often resort to an
old trick a caster once showed a friend of mine, that their casting
house used to save porous castings.

I made a series of rotary burnishes, by annealing old burr and drill
stems, bending them to 90d at the end, and pollishing the short end
of the bent stem to a ball shape. I then re harden and then put a
medium temper on the new burnisher, to prevent shattering.

With these rotary burnishers in a flex shaft, at medium speed, I work
a pitted area of a casting, burnishing the pitted areas in all
directions, lightly, just prior to the final polishing, to close any
surface pits, and then I lightly rubber wheel and pollish this area.
The pits remain, just below the surface, and any heavy handed
polishing will re expose them, but the work hardened surfae is
actually quite durable.

9 
I have a sterling silver ring I am looking to make the master copy
for a silicone mould. Problem is there are a few porosity holes
less than.8mm in diameter that will need filling. Anyone got any
tips or tricks before I make a mess of it trying to fill it with
easy solder?

Don’t “just fill’em” with solder. Drill them out with a tiny ball
bur, then make tiny balls of silver and fit them to the holes, then
solder it together.

Ray Brown

10 
If you can keep the flux in the cavern it is best I think.
Sometimes I find it helpful

Just a random quote… I guess it’s why they call us old-timers :}
It’s truly a trick, I guess:

Just mold the piece, and then after it comes out your porosity will
be little dimples in the rubber - positives from a negative space.
Then just clip them off…

It works better in standard rubber because you can melt it to be
truly smooth. Silicone you can’t do that, but you can clip it.

Yes, it’s better to fix it first, but there’s times…

11

Thanks for the varied and helpful replys! I never knew there were so
many ways to fill porosity. For the purpose of making a mould and
not having the porosity show up on copies, would the quickest,
easiest and safest way, be the epoxy? It will shape and finish ok?
Although, now that I think of it… if I’m casting them, filling
porosity with silver might be something I should get used to :slight_smile:

12

If you just want to make a silicon mold of the ring, fill the
porosity with a soft wax. Once you make the mold, the porosity
should be unnoticeable in the wax models.

13

James,

Yeah, the old “bent nail” trick is a reliable one for getting out
minor surface porosity. As simple as annealing a nail or broken bur,
put in a vice and bend it over. Cut off the short end, file, sand,
and polish the tip to a round, smooth, tip, and you’ve got a
“porosity remover”. I don’t even bother to re-temper the finished
piece, and I’ve had mine for at least 20 years with no problems.

The idea of just having a small simple tool, rotating in a handpiece
to compress metal is a simple concept, and a life saver when you are
dealing with some minor surface porosity.

Jay Whaley
Whaleyworkshops.com

14

Hi Zanes;

That’s an old trick and a good one. I’d like to add a few pointers,
if you don’t mind. When you do this rotary burnishing technique, use
an old number thiry hand piece. If you use your nice quick change,
you’ll beat the bearings to death over time. You can also use a
hammer handpiece with a straight bit with a rounded and polished end
and just planish back and forth across the porosity.

Also, I’ve found the after burnishing, rubber abraisive wheels tend
to pull up the porosity all over again, as they contour themselves
around the hard areas and cut down into the spongy places. Better
results from going through finer and finer sand paper, ending with at
least 600 grit, then a quick hit with tripoli and finally rouge.
You’re right, stay on it too long and hard, the porosity comes back.

Finally, don’t bother trying to fill porosity with solder, it’s a
waste of solder as it can’t really wet properly over a porous area
because of escaping gasses. Maybe after you burnish it down, if
you’ve sealed it up well, you can fill a small low area with solder,
or, of course, laser weld.

Finally, it’s always a good idea to see if you can learn why there’s
porosity there in the first place. Mold too hot? Improper sprueing?
Contaminated metal? Abrupt changes in mold thickness? Look at the
pososity under a loupe. Is it from gasses or shinkage? Gas porosity
looks like tiny pinholes. Shrinkage leave spongy areas, often near
the sprue or where a thin area is next to a thicker one.

David L. Huffman

1 Like
15 
if I'm casting them, filling porosity with silver might be
something I should get used to :)

Maybe better still would be to improve the castings…

tongue in cheek :stuck_out_tongue: