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Exploding hollow bodies


#1

Hi,

in my first semester of metal design studies I was told to
always drill a small hole into fabricated hollow bodies prior to
soldering to prevent the piece from exploding. Due to the air
enclosed expanding while heated, it possibly might burst the
piece. The small hole then should be closed in a second
soldering. Since then I never ran into difficulties of making
some hollow bodies but now I am and I’m wondering if something
like this really could happen. What is happening when you’re
closing that small hole? Why should the danger of exploding not
be present then? The piece gets heated and the air expands, too.
Maybe the whole “exploding story” is just some kind of legend to
scare newbies… I’d really like to solder my pieces without
that drilled hole, because that always would be visible (working
in sterling) and there no hidden place where I could place it.

TIA,
Sabine

sabineas virtual gallery
metal design, jewelry & silverwork
http://www.sabinea.com/

Moderator’s Note:

Discussions over this topic took place few times over the last
couple of years at the Orchid forums. You can retrieve
the threads by running a keyword search.

http://www.ganoksin.com/orchid/archive/

Best Regards
Hanuman


#2

As I’ve had a hallow earring " explode ", I can say that small
hole is a really good idea. I make mine with a very sharp used
burr that was broken. Jus tground it down to a nice sharp point
and put it into a pen vice. Drilling it works too, but then you
have another hole to deal with. It does’nt need to be that big
just enough to let gas escape. I try to put ti where it won’t be
seen. If you make it small enough it’s not noticiable. Good luck
and keep it shiny,…Matt the Catt


#3

Hi Sabinea,

The best way to see if drilling an air hole (in a hollow object
to prevent explosion) is just a load of cobblers, simply make up
a hollow object and don’t bother with the safety valve air hole.

Here’s a cheap little project which will guarantee results: make
a small sphere around 12mm in diameter out of 1.0 mm brass,
soldering the two hemispheres together with medium silver solder.
Remember not to drill that air hole!

Now solder the sphere to a small piece of flat plate or a ring
shank with easy silver solder. For safety’s sake I’d suggest you
wear some eye protection at the very minimum.

When your ears have stopped ringing, drop us a line and let us
all know what happened.

Kind regards, Rex from Oz-Australia


#4

Hi Sabine,

Hollow pieces can in truth explode under certain circumstances.
I was soldering a half inch silver dome onto a sheet of silver
with a circle of half round wire on edge as a frame for the dome
and at some point in the process, there was a sound very akin to
a 38 caliber handgun going off in my face. After I recovered
from being stunned for a few seconds, I looked at the dome and
there was a round hole with jagged edges ripped into one side.
It looked like a bullet hole on the opposite side from the
impact side. I was lucky. I could have gotten red hot metal onto
a variety of places on my body, including my eyes. I don’t know
all of the factors that went into this event. I’ve done similar
things before without the explosive outcome.

I sometimes drill tiny holes in places to let steam escape. They
are sometimes possible to disguise, depending on the design.
I’ve been able to drill them in the place where a bezel is
soldered on and then cover the hole with the set stone. They can
be very tiny, the tiniest drill you can find. I’ve also had luck
filing a very small groove with a file in one edge of the
construction that later fills with solder. Another disadvantage
of leaving the hole is that pickle gets inside and can cause
problems later. I try to neutralize it with a syringe and baking
soda, but it can sometimes be a challenge. I heard somewhere
about putting a wire that is the same size as the hole in a flex
shaft and spinning it in the hole and it somehow locks in place
and can be filed flat, but it didn’t work for me. I must not
know the trick, or it is just an old jeweler’s tale. I’m looking
forward to other responses to your questions. Don’t be afraid,
but be careful.

Jima

Jima & Carlie Abbott /N. Calif/ @jica
check out our work on the web at:
http://www.artmecca.com/artwork/jica.htm
best viewed at 800x600


#5

Sabinea, believe me it does happen… once while repairing a
hollow charm… Snoopy went BOOM…it wasn’t a pretty sight. I
like you thought it wouldn’t happen…it did and now…I drill
the hole!!! Keep drilling,
Sharon.


#6

Sabine:

I never had a hollow piece explode like a bomb on me ( I have
had teachers who claim it has happened to them) but I did have a
hollow object without a hole that I was soldering start to shake
so violently I quickly ducked under my bench to avoid a possible
explosion. Ever since I always make sure I have a tiny hole on
my pieces. Later I plug it up with a dot of gold. It is like a
nice little surprise on a silver piece.

DeDe


#7

Drilling a hole in a closed form is a good idea for several
reasons. One, you don’t usually know what type of gases may be
trapped inside from previous operations, manufacturing or
repair. Perhaps a volatile combination was trapped inside. And
another pesky problem with a closed form is that you lose
control of your soldering due to the fact that gases are
expanding and blowing through your liquid solder when you least
expect it. So drilling a hole relieves the gases whilst you
make your repairs/welds elsewhere on the piece. Then you solder
the small hole. You will often notice a small contraction of
the small soldered hole as it cools due to the cooling of the
air/gases inside the form.

John g


#8

Hi Sabine.

I too have experimented with hollow, non-pierced forms and also
was warned against this happening. And it happened to me while I
was making a hollow ring. I was just finishing sealing the edge
with solder when it popped right open. It wasn’t large or
dangerous, but then, it was a very small ring. I was told it
wasn’t the heat inside, but rather the WATER in it that did this
(steam being a powerful force), but I’m not sure if air would do
the same thing. I would imagine from my purely Chemistry
background that air wouldn’t expand enough under heat to pop open
a ring; however steam and other vapours might (and did…sigh).
At any rate, to prevent this, I just drilled a small hole
underneath the seat of the ring. Keep in mind it doesn’t have to
be a very big hole… I’m not sure what to tell you about hiding
it. At any rate, it can happen. Good luck :slight_smile:

					-Kieran

#9

Many years ago I tried to solder an ear post to a hollow
earring. Just when the solder started to flow, the piece
literally blew apart at the seam making a VERY loud noise. My
ears were ringing .

A small escape hole would have allowed the rapidly expanding air
to escape freely . When you plug the hole, there is actually some
negative pressure inside the piece but not enough to cause it to
collapse (implode). The inside pressure may equalize over time
by air entering the piece through very tiny pin holes. This is
why you’d need to drill an escape hole for later repair work.

In assempling a new piece, it may not be necessary to drill a
hole. The seam itself is a pretty large hole, expanding air can
vent through it. If it’s large and thin walled, you may need the
hole to prevent implosion upon cooling. A good way to hide this
hole is to make it along the seam in the least noticeable
location possible.

For earrings you can drill the vent hole at the attachment for
the post/finding so that it’s soldered shut with the attachment
of the finding.

Hope this helps.

Wayne


#10

Since then I never ran into difficulties of making
some hollow bodies but now I am and I’m wondering if something
like this really could happen. What is happening when you’re
closing that small hole? Why should the danger of exploding not
be present then?

Sabine, when you’re soldering shut that small hole, you’re sort
of reversing what happens when you heat a closed body. The trick
is that until the hole is closed, there is no pressure problem,
due, of course, to the open hole. And in soldering it shut,
you’re sealing the hole while the item is hot, so the air is
already somewhat expanded. If you were then to take the
now-sealed piece, and solder somewhere else, much more strongly
heating the thing, you might get the inside air hotter than when
you sealed the hole, and then it might indeed burst, but aside
from that, when you seal the hole, that’s the hottest it’s
supposed to get, so as it cools, the now sealed form develops not
pressure, but a partial vacuum inside. This might slightly
collapse a sufficiently thin form, but it won’t burst it. And you
could even reheat the thing somewhat, which would only equalize
the original pressure, so long as you don’t exceed the original
temp it had when you sealed the hole. But heating a sealed form,
especially if, in sealing it, you accidentally got some liquid
inside, forming steam, can create pressures much higher inside
than the partial vacuum you can develop in sealing the hole. In
initially soldering shut a hollow form, you usually also have a
similar situation, but often, you’re soldering large seams, with
more heat, etc. And what happens is that sometimes that partial
vacuum that forms as the piece is cooling, sucks just a trace of
the solder away from the seam while the solder is still sludgy
and not quite solid. This can create very tiny microscopic
openings that nevertheless equalize most of the air pressure.
But the piece is still hot, right? So innocently, you dunk it in
water or pickle… Looks fine. But this last bit of cooling and
the additional partial vacuum it causes just sucked a bit of
liquid into the pore and inside the piece. Now in polishing and
finishing, maybe you burnish that pore down a bit, or clog it
with polish compound, etc. Or maybe a bit of the pickle, later
leaking out just a tad, dries/crystalizes, plugging the pore.
Anyway, it’s easy to end up with a sealed form with normal air
pressure inside it, no real means of letting air in or out
quickly, and yet a bit of moisture inside. If you then heat
this up again, in another assembly step, when the moisture boils
to steam, it quickly can build up to quite high pressures. And
THAT is what can give you rather dramatic results. Even without
trapped moisture, heated air can compress to significantly high
pressures. I’ve seen pieces pop with enough force to pretty
much destroy them, sometimes even creating a safety concern for
the person doing it. Other times, it just opens up a previous
solder seam again. Either way, it’s best to avoid this
happening. If you’ve made a hollow form, be sure there is at
least some, clear way for pressure to equalize before heating it
again. Doesn’t take a large hole. sometimes, it doesn’t even
need to be soldered shut. Can leave open, or just burnish it
shut if you plan it right. Often the open hole can be hidden
inside some finding or stone setting, or mechanism, or the like.
You don’t always need to actually drill it either. If you
simply file a small notch, or the start of a saw cut, in an edge
before soldering the thing shut, that tiny notch will form a tiny
gap in the solder seam. That’s often enough, not then needing an
actual drilled hole.

Hope this helps.

Peter Rowe


#11

For a wonderful article on hollow spheres check out Lapidary
Journal, June 1998 by Holly Lee. She doesn’t say to place a hole
in the form before soldering but I’m sure she does. This article
will help you fit both pieces together without a problem.


#12

The fact is that it WILL explode!!! A friend of mine had a dome
being soldered onto a flat back and she said it was like a gun
shot when it exploded. upon examination of the piece (when she
finally found it) it looked like “fish lips” (she showed it to
me). Very scary!


#13
 What is happening when you're closing that small hole?? Why
should the danger of exploding not be present then?  *SNIP* 
I'd really like to solder my pieces without that drilled hole,
because that always would be visible..

Presumably, the air is escaping through the seam around the plug
you are soldering into that hole. When the solder flows and the
form is truly closed, you remove the heat and the air is no
longer expanding. I solder closed forms with no trouble (and no
holes). Closing the form is always the last step, though.
Anyone out there think I’m standing in harm’s way?

Dana Carlson


#14

Hi Sabine, I have always drilled a small hole also. This
exploding hollow bodies are one of the reasons that I said the
"steam is one of the most powerful forces on Earth." in my steam
casting articles. It really is scary. In a future article on
steam casting I will confess to a really stupid thing I did in
college. Just for fun I threw an ice cube in to about 100 lbs of
molten lead! I did it, just to see if all these stories I was
told about how dangerous water around molten metal were true. It
was a good thing that I did it in a small room, with all brick
walls, no windows and one door. I poured the lead into a mold
that made pigs for a Linotype machine, about 100 pounds. I went
out the door, threw the ice, closed the door and - well stay
turned to the steam casting articles.

Don Norris
@Donald_Norris
PO Box 2433 Estes Park, CO 80517


#15

Hi Dana, I doubt you are in any danger. The air inside a hollow
form expands when you heat it. This expansion is complete before
you finish soldering, so no problem. If, however, you go back
later and reheat the form, the air inside will have no place to
go and it might blow. Always drill a small hole first if you are
going to reheat [as in doing an alteration or repair]. Have
fun. Tom Arnold


#16

I thought I was the only one who did this. After reading all
the terrible things about soldering hollow things, I have never
encountered problems with soldering shut with a post finding.
Glad to know that there is somebody else out there who also uses
this practice.

Karen Christians
M E T A L W E R X
416 Main St.
Woburn, MA 01801
781/937-3532
http://www.metalwerx.com/
@metalart

Current Artwork:


#17

Yes, they do explode. I almost lost my eyesight as a result of
it! I was trying to solder a post back on to a silver hollow
earring I was repairing and BOOM! Also sometimes those things
are filled with some sort of goo to make them more rigid and it
stinks to high heaven and is probably toxic. Now I refuse to
repair those silver earrings like that and I tell my customers
with gold hollow earrings that there will be a small drill hole
on the back. Wendy Newman


#18
  Sabine,  when you're soldering shut that small hole, you're
sort of reversing what happens when you heat a closed body. 

And then about another mile of the same…

hey folks. Did anybody understand what i was trying to say in
this post? I think it may have made some sense somewhere, but
now I’m not sure just where, or more to the point, why I couldn’t
say it in about two short paragraphs…

Just goes to show. You can get REALLY buzzed out of your skull
on the antihistamines, cough suppressants, and other stuff you
take to try and function when suffering from the flu. At the
time I wrote all that confusion, I suspect it’s a good thing I
was running a keyboard and not a torch… (grin).

Feeling much better now, thanks…

Peter Rowe
aaaaachooo


#19

Also be careful of hollow bodies that don’t look like hollow
bodies. When I worked in a tradeshop, the jeweler next to me was
repairing a class ring. A so called jeweler in a store had tried
to stretch it up on a Kagan and split it though the shoulder.
While it was being soldered the stone in the top shot out of the
bezel, sounded like a .22 going off. I swear the guy rose three
feet into the air! He came crashing to the floor bringing his
bench pan and all it contained on top of him. He was covered in
tools, alcohol, flux, and the can of tobacco juice that was on
his bench. Once I stopped laughing (quite some time) I dug the
stone out of the drywall, it almost went all the way through.

Although not dangerous, I had my own run-in with a hollow body.
I had a job to size up 1/8 size. I threw it on the mandrel,
whomped with my hammer, and it went thud instead of ting. The
darn shank was hollow! The customer got their money’s worth on
that job as I had to replace the shank with a solid one, for all
of $6.50!

Brett Gober
Freedom Design & Contracting


#20
Also sometimes those things

are filled with some sort of goo to make them more rigid and it
stinks to high heaven and is probably toxic

Some of those filled ones are not filled as a seperate
operation. They are made as electroforms, and it’s easier and
cheaper to simply leave the molded form over which the silver is
electroformed in place, in the form, rather than remove it. Also
lets em grow the things even thinner and cheaper…
electroforms, by the way, are often very thin, yet the nature of
that type of deposit is that the metal comes out of the bath very
hard, almost brittle sometimes, so that they are strong enough to
work as jewelry despite their light weight. Repairing these, or
any form of soldering operation on these electroforms will
anneal this hard metal, and the result is a piece of useless
flimsy foil that will dent if you breath on it hard. Repairs to
these things need to be done only at low temps if you hope to
retain the wearability. It’s one of those times when, if you
replaceing a broken ear post, for example, a soft solder type or
even a glue on is the best choice. On a few of them, if there’s
an existing thicker pad of some sort to affix to, you can also
get away with a fusion post, if you have a fusion welder like a
sparkie. that won’t anneal the electroform. but it needs
thicker metal to weld to than most of the basic electroforms
themselves.

Hope this helps.

Peter Rowe