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Cracked silver


#1

Today I was annealing some silver prior to rolling it out in order
to obtain a thinner gauge.

The first annealing, and rolling went well. However on the second
annealing to my dismay the piece of silver, which was about 3" by 5"
split across the middle. A nice clean break., This happened while I
was doing the annealing. The piece was slightly arched in the middle
from the first rolling, and I had gently pressed on it with my tongs
to flatten it. I have done this before, but never had this happen.

The only thing I can think of that I did differently is that I had
quenched the piece after the first annealing while it was still hot.
Usually I let it air cool. Could this have weakened the molecular
structure?

Alma Rands


#2
... A nice clean break. This happened while I was doing the
annealing. The piece was slightly arched in the middle from the
first rolling, and I had gently pressed on it with my tongs to
flatten it. 

This is the kind of thing I’ve had happen with Argentium. Perhaps?


#3

Assuming this is sterling you are talking about, yes if the metal was
too hot when you did this you absolutely could fracture the crystal
lattice. Sterling is hot short and will crack if it is manipulated or
quenched when too hot. You need to be very careful with your
temperature when hot working sterling. You could have done the damage
either when pressing on it or when quenching or it could have been
the combination of both events.

James Binnion
James Binnion Metal Arts


#4

Hi Alma,

Thank Charles Lewton Brain for this one. If you work metal,
annealing, rolling, etc., and you don’t quench the metal, the
crystals in the metal will expand and create cracks and breakage.
Quenching, minimizes crystal growth.

There is a fine line between just soldering a piece and then
quenching. You don’t want to thermal shock the solder, but if you
wait just 3 seconds, it’s enough time for the solder to gather,
especially easy and then quench your piece.

As one of the demo pieces for my soldering class, I have a piece I
was working on that did just what you described. Actually I was
shocked, because I’m pretty good on the soldering front. The end of a
curved 20 sheet, just cracked off. Wow, I never had seen that happen.
A custom commission just became a teaching tool.

While annealing in highly lit rooms, it’s tough sometimes to make
sure you don’t pass the annealing point and over heat your metal. A
Sharpie Marker is great as a temperature indicator (yes, another CLB
trick). I can’t always make the distinction between perfectly flowed
flux nor trust my aging eyeballs!

Karen Christians
Cleverwerx


#5
Thank Charles Lewton Brain for this one. If you work metal,
annealing, rolling, etc., and you don't quench the metal, the
crystals in the metal will expand and create cracks and breakage.
Quenching, minimizes crystal growth. 

Karen this is just not right. Cold work (rolling bending hammering
etc) deforms the crystals in the metal making them thinner in one or
more axis depending on what you are doing. This puts strain on the
crystal lattice and makes it hard as the more distorted the lattice
the harder it is to further distort it. By heating the metal the
lattice “recovers” as the crystals reshape themselves as the atoms
can move about more easily as the temperature increases. If you put
enough cold work into it then new crystals will form as it is easier
to form new small crystals than to recover the original crystal
shape. Heat it too much and the crystals begin to grow. This is the
only way to make the crystals larger, by heating to high temperatures
(beyond what is needed to anneal) for extended periods of time.
Cracks can come from many sources but not in this case from lack of
quenching. If you don’t quench certain gold alloys you can end up
with brittle metal but not from crystal growth and sterling will be
slightly harder if air cooled than quenched but it is a minor
difference and certainly not brittle or prone to cracking.

James Binnion
James Binnion Metal Arts


#6
The piece was slightly arched in the middle from the first rolling,
and I had gently pressed on it with my tongs to flatten it. I have
done this before, but never had this happen. 

This formation of a raised area in a flat sheet indicates that the
metal reacted differently to the rolls here. It sound as if you are
saying arched parallel with the direction of rolling. A small air
bubble in the original ingot is a likely cause. After repeated
rolling and annealing the bubble stretches into a line and
eventually the wall of the bubble thins enough to break. There are
other possible causes related to over heating when annealing or other
impurities in the ingot.

One, less common occurrence, is related to continuous casting, and
the need for absolute temperature controls during the process and
proper mixing. Some companies have better results than others in this
respect. If you roll perpendicular to the original casting direction
the fault would produce this type of failure.

Daniel Culver


#7

Hey Alma, the only time I’ve had this problem has been with
Argentinium. I’ve put normal silver through a lot when using the
rolling mill and have never known it to crack (apart from when doing
mokume gane) I didn’t realise I was using Argnetinium at the time.
Hope this helps?

Laura-London


#8

Thanks for all the feedback on my cracked silver (sterling). After
reading the various posts I have come to the conclusion that I
overheated the silver I am almost always very careful and watch the
color change. This time I was in a rush to get things done as I have
a show coming up and had turned the torch full blast on the silver
thinking to speed up the annealing. Bad idea. Lesson learned, Haste
does indeed screw things up.

Alma


#9

Jim,

Assuming this is sterling you are talking about, yes if the metal
was too hot when you did this you absolutely could fracture the
crystal lattice. Sterling is hot short and will crack if it is
manipulated or quenched when too hot. You need to be very careful
with your temperature when hot working sterling. You could have
done the damage either when pressing on it or when quenching or it
could have been the combination of both events. 

This was the case for my piece. There was no cold forming except the
initial gentle bend. I was making a complex curved bezel to a curved
back plate for a piece of curved pottery. I think the tip of the
triangle back plate got overheated while making sure that the large
bezel was soldered securely. One tiny spot did not solder flat to the
base and in doing the last solder operation, too much heat the tip
caused it to break away.

karen christians


#10
Sterling is hot short and will crack if it is manipulated or
quenched when too hot. You need to be very careful with your
temperature when hot working sterling. You could have done the
damage either when pressing on it or when quenching or it could
have been the combination of both events. 

I too learnt that sterling silver is brittle at red heat, the hard
way. When I was a new and very young apprentice I was very pleased
to get to make my first chalice. Particularly because it was quite a
complicated design with a hammered hexagonal base. One problem was
to get the bottom of the base perfectly flat to meet the edge wire. I
noticed the experienced craftsmen had a trick to do this. They
annealed the base on a flat fire brick and then would press down
with another brick. This would flatten the edge without the need for
further adjustment.

I placed my chalice base on the brick, heated until it was at a dull
annealing temperature, placed my brick on top and pressed down. My
chalice base shattered into about forty pieces. I had failed to
notice that the experienced craftsmen waited for the red heat to
dissipate, before applying the pressure.

Peter Johns


#11

What is the Sharpie test for indicating annealing temperature?

Barbara


#12

Barbara,

I have heard instructors tell their students to put a stripe of
Sharpie pen ink on a piece of silver to be annealed, and when the ink
disappears during heating, that is a sign the silver is annealed.

I don’t subscribe to that technique, personally. I have had students
who did that, but their sterling silver never got hot enough to be
truly annealed. So, rather than look at ink on the metal, I advise
watching carefully for the silver to get a dull rosy glow, to be
really annealed. In my studio, I use a small metal box, lined with
Solderite boards, for doing our annealing. (I use an Army surplus.50
cal. Ammo box with the lid removed, turned on its side. It’s size is
just perfect, and made of heavy steel.) In that way, using a torch,
the metal being annealed is in an enclosure in a “shadowed” area, so
seeing the metal’s true color is much easier than annealing in
normal room light.

I use a Sharpie pen all the time in my studio, for marking on metal.
For instance, when marking a line on a sheet of metal, I will color a
field of black with the Sharpie, which dries nearly instantly, and
then I can scribe a fine line into the black Sharpie ink field. This
line is perfectly accurate, and won’t rub off while working. The ink
removes easily with alcohol and a rag.

I have Sharpies all over the studio, for easy access.

Jay Whaley


#13

Hi Barbara,

What is the Sharpie test for indicating annealing temperature? 

When the black mark is completely gone, your metal is annealed.

Karen Christians
Cleverwerx


#14

You simply mark the item that needs to be annealed with a Sharpie
marker. Then heat it evenly with your torch and the Sharpie ink will
burn off. That is when you have reached the annealing temperature.

Norine


#15
What is the Sharpie test for indicating annealing temperature? 

Make a line on your metal with a permanent marker. When the line
disappears, the metal has reached the correct temperature, remove
the flame.

Elaine
http://www.CreativeTextureTools.com


#16
When the black mark is completely gone, your metal is annealed. 

Not necessarily. If you cover the sharpie with flux it will survive
the annealing process well enough to still be somewhat visible. And
if you don’t use flux, well you have heavily firestained silver. It
is much better to just learn to read how the metal and flux look when
annealing to judge temperature.

James Binnion
James Binnion Metal Arts


#17

Jay,

Thank you for your good post. I understand your reasoning. However,
I have found with students that seeing and interpreting the correct
color of annealed metal in brightly lit studios, classrooms, etc.,
this is a good way for beginners to work towards seeing their path to
understanding how metal heats. The technique you describe, creating a
shadow is excellent, but students are often impatient and that
Sharpie mark just allows them to slow down and think about what they
are doing.

I found what works best in teaching is to use a combination of
Sharpie and a little flux. Under-heating is better than overheating
when silver can crack. The dull rosy glow has also been described as
dark Bing cherry. I use Superior Six paste flux which spreads out
beautifully when the temperature is right on.

A student once heated her silver to bright screaming red concluding
that the “red” should be more Maraschino. Those belong in my Whiskey
Sour and not part of fabrication.

I didn’t want to imply that the Sharpie is THE way to make sure your
metal is annealed, but rather one route to a goal.

One thing for sure, you are correct on Sharpie Markers. Maybe we
could start a theme of “100 Uses for Sharpie Marker.” They are very
helpful for students in seeing how evenly they are filing and sanding
and the scribe line you mention is quite helpful.

Karen Christians
Cleverwerx


#18

Hello all,

Charles Lewton-Brain told me 'way back in the 80’s that the Sharpie
mark was great for the annealing temperature of Aluminum but only
Aluminum. I know for a fact it doesn’t work on sterling, the metal is
still not annealed when the mark has disappeared.

Brigit


#19

Wow, for us newbies all these conflicting ways is very
confusing…Valerie


#20
I know for a fact it doesn't work on sterling, the metal is still
not annealed when the mark has disappeared. 

I still feel that it is a very good learning tool for beginners. The
silver may not be totally annealed, but I would say it is at least
substantially improved. Plus, the student has an easy-to-judge
guideline to use to begin to get a sense of how much heat it takes to
anneal. This prevents a lot of over-heating from not being sure when
to stop. As they begin to get a sense of what the metal looks like as
they watch for the Sharpie mark to disappear, they can stop using it.
It increases confidence at the beginning of the learning curve. All
in all, very useful!

Noel