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"Fixing" porosity


#1
   Have any of you had better luck repairing this sort of
really severe spongy >porosity?  If so, how, and with what sort
of welding paramaters? (voltage, pulse length, focus diameter,
etc)."  

I don’t have any laser welding experience at all, but I’ve
"succeeded" (the porosity remains inside, so it really isn’t a
success) with combination of lower tech methods that should be
helpful for craftspeople with somewhat less than a laser.
Additionally, this method doesn’t require heat so it doesn’t
cause firescale - covers firescale infact - and the added metal
is of higher purity than the metal you’re repairing, so it’s
still legitimate. (Better than flooding with low carat alloy, or
cadmium solder with silver)

As Peter described, peen and burnish to close the pores near the
surface as much as possible, but then don’t sand or buff it quite
yet. Electroform a skin of new metal over it.

Actually you might start by electroforming before the first
burnishing. Chemically clean the metal with a strong pickle, then
ultrasonically clean out the pickle with water. Rinse in Hot
water or steam it, dry, paint nail polish on the areas that you
don’t want to electroplate. Keep the metal scrupulously clean of
oils from finger prints etc (wear rubber gloves with cyanide
plating solutions, avoid mixing pickle and cyanide, maintain
ventilation etc., etc. )

I use pure gold or fine silver annodes, but it should be
possible to electroplate an alloy, I just haven’t bothered.

Set the electrical source - I use a cheap Radio Shack� power
supply set to 3 or 6 volts, DC, and a reostat with a couple of
meters on a strip of plywood - cost, about $20 - to the
appropriate voltage for the area you’re working on (this can be
determined by formula, but trial and error works for me) and
build up a deposit on the surface of the porous casting. It won’t
fill in the pores because it will preferentially plate on the
high spots, but that’s ok because the next step is to burnish
that raised newly plated metal down into the microscopic holes,
Repeat several times until the burnishing fills the pores and the
plating grows together to form a continuous skin and then plate
for a longer while, over night if necessary. Smooth the surface
with burnishing and 1400 grit wet/dry sandpaper.

Of course by then you’ve had to repaint the nail polish several
times as it peels or blisters. Removing nail polish is easy, hot
water and the ultrasonic cleaner will usually lift an edge that
you can grab with a tweezer and peel. For a complete removal,
soak in acetone.

None of this is fast, admittedly, but it’s at least a way to
save an otherwise lost piece, and most of the plating time can be
unattended. I’m in the process of doing this right now with a
special silver watch case that entails enormous labor; I will NOT
GIVE UP! I find that I can produce what appears to be a perfect
surface . . . with lots of elbow grease and hand sanding. Plus,
in silver, the color is whiter and doesn’t tarnish as fast as
sterling.

Alan Heugh
http://www.nas.com/~aheugh/

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#2

I am new to the forum so please excuse me if this is common
knowledge.

I get rid of casting flaws using a simple and low tech method.
It is as follows: take a 2 inch nail and cut the head and point
off with a hack saw. You should have about 1.5 inches left,
round and smooth one end, heat the nail to red hot and bend the
nail apx 1/4 inch from the end that has been rounded, plunge the
nail into water, dry.

Put the nail in to a Flexshaft or Dremel unit. Using the
spinning short end as a (sort of) spinning hammer/burnisher work
the metal around the flaw in towards and over the flaw (make
sure to circle the flaw, not simply working in one direction),
once you can no longer see the flaw sand the area smooth and the
flaw will be gone.

You may need to play with this a bit but it is well worth it. I
have closed some rather horrific holes/flaws in castings using
this method.

B Goodman, Van. BC

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#3

Hello All,

The best way of taking care of porosity is … don’t
create the chance of getting it !!In honnor to my customers,I do
not deal with this kind of treatment.If you sell your jewelry
and you work with proud something inside of you should keep you
from doing this.If you still want to sell it because you spend a
lot of time into this item,then you should tell the people what
the deal is and lower the price.I understand perfectly that time
is money but this doesn’t justify the practice of hidding
imperfection for customers. I’m not mister perfect and I to make
faults or have malfunction in castings occasionly,but I try to
repair the imperfection instead of hidding it.If I can’t
… bad luck for me but I’ll remelt it and start
troubleshooting. Sorry of beeing so direct,but the information
about porosity and the solutions to solve this cause are more
then enough explained by several known AND unknown goldsmiths.So
it’s up to us who’re having trouble with this typical casting
problem to learn from it and use the to make our
creations made by craftmanship and knowledge more desirable as
they already are.

Regards Pedro
Palonso@t-online.de


#4

Pedro, I hope you do not take offence at the following but I
completely disagree with your position. You seem to imply that
some of the suggestions for dealing with porosity are bordering
on being dishonest. If the item was somehow structurally
unsound, or was not able to serve the function for which it was
created, then yes, I would agree with you. However, the
objective (as I see it) is to create a piece of jewellery which
is true to the designers vision. If burnishing a piece allows
the artist to eliminate a flaw on the surface that would
otherwise constitute a defect in the finish then why would that
be deceptive. There is no intent to deceive, its not like hiding
a chip in a stone under a claw so that the customer is in fact
purchasing damaged goods. Burnishing, soldering,
electoforming/plating, or using laser welders is part of the
process of achieving the finish desired. Many of the ideas and
techniques suggested are highly creative solutions to a common
problem with cast items. Personally I congratulate those
individuals who devised and utilise these techniques. I once met
someone who refused to polish using a motor. All polishing was
done exclusively by hand. His attitude was that a motorised
polishing unit was somehow cheating, and those who utilised such
practices were creating inferior items. Well, each to their own.
I take great pride in my work, its the finished item that
counts, if it is true to my vision, then I am well pleased to
offer it for sale.


#5

Your tool designed to remove poracity marks does indeed work
very well. We call it our “beater” bar and we count on it to
remove casting flaws caused by metal cooling as well as small
impurities that may find their way into the casting.

We have found that it works even better if you can somehow hold
the casting in place against a heavy object that will not move
such as an anvil while you use the beater bar in the effected
area. It seems to have much more control as well as speeds up
the time necessary to work the gold or platinum.

K. Reid


#6

Hello Goodman,

As long as people use their mind more then their mouth,then they
will not offend other people and I like to exchange idea’s and
thoughts anyway. I think that we’re communicating at the same
level and the same direction.If you work with honnor you will
ALWAYS try to find out why or who to produce a casting without
porosity.I have seen porosity in jewelry work and the goldsmiths
(yes ,more then one !!)tried to hide it with all kind of tricks
to cover the pits of a bigger size Regards Pedro
Palonso@t-online.de


#7

B.Goodman, I quite agree with all your contentions about
finishing with one major exception…plating. I personally
perceive plating to be the greatest dishonesty of all( short of
outright misrepresentation). Have you ever heard of a jeweler
telling a customer “This finish is not what you are going to
have after a few months wear…it has been electroplated to give
it a brighter look and more intense color” ? Let’s be honest
about this…when you flash plate a twenty-four k layer on a 14
k ring you ARE deceiving the customer and the intent is to “gild
the lily” so as to seduce the customer ! Ron at Mills Gem, Los
Osos, CA.


#8

Pedro, I will have to agree with you on some accounts,
HOWEVER… As a jeweler working in metals, sometimes you do get
imperfections in the metals. Note that some people in these
threads are “hiding” the imperfection, while others are indeed
"repairing " the imperfetion to the best of their ability. so, if
I can actually fix a porous casting with my laser…I will take
that rather than reordering or recasting a piece. I will not
take less on the piece because I took my time and my effort to
repair it. Not everything in this world is perfect …as a
matter of fact…very few things in this world are
perfect…and if perfection out of reach is what you are
reaching for, you will be sitting there casting that same ring
until doomsday. -julia


#9

Sorry, Palonso. I suspect that there is some misunderstanding
about what burnishing is. I routinely burnish freshly cast goods.
Usually, I will burnish the inside of the ring. After I have
pounded down all of the irregularities that are indigenous to
lost wax casting, I will round up and size the ring. Since I
usually try to do the wax about a half size smaller than I need
the ring, I will hammer the shank with a metal hammer to round
the ring up to size. I will next burnish the edges and lastly
the outside of the ring. For areas that I cannot reach with my
routine burnisher I have heavy steel brushes and a couple of
smaller needle like burnishers. Afterwards tripoli and rouge will
usually finish things off nicely. Occaisionally, during the
process, I will anneal, pickle and clean my work. For about
fifteen years, I didn’t use a burnisher. The result was an
ungodly number of rejects, not to mention the stuff that I sold
anyway. I know that that my mountings have superior quality,
because: 1. I have subjected them to a rigorous form of abuse
thus exposing hidden flaws. 2. Burnishing has provided the
equivalent of rolled surface to irregular surfaces. Sometimes
the burnished surface extends .5 to 1mm into the casting. 3. Less
metal needs to be removed during the finishing process. Tumbling
with shot has the same effect, but requires a lot more time to
get the same effect. Bruce


#10

Julia, I agree with what you say about “repairing” in
imperfection in a casting etc. Normally when doing a commission
job, I cast only one of something. In fact, I usually only have
one wax of the model to begin with and to do the whole thing all
over again would not be cost or time effective.

In those cases where the problem is in a solid area of the
shoulder or in the shank I drill out the porosity, force a tight
fitting piece of round wire into the hole and apply a very small
amount of hard solder. If done properly, the repair will be
totally unnoticeable and it is more durable than the "beating"
method. “Beating” can be useful however, when the problem is
small, isolated, or in a spot where drilling is not practical.

Cheers from Don at The Charles Belle Studio where simple
elegance IS fine jewelry!


#11

Actually Ron, while we do very little plating we do get people
who insist on white gold. Since we only use 18k palladium white
gold and it isn’t truly white, we do offer to them the option of
having it rhodium plating. However we DO tell them that it is
not permanent and will need to be redone on a regular basis. As
with all treatments, permanent and not, AS LONG AS THEY ARE
PROPERLY DISCLOSED, there is no deception involved. So
apparently there are a few jewelers out there who say “This
finish is not what you’re going to have after a few months wear”.
Incidentally we say the same thing to them when they want any
stones other than diamonds, rubies, and sapphires in a ring,
because the reality is that in 2 years that tourmaline will NOT
look the same. Daniel R. Spirer, GG Spirer Somes Jewelers 1794
Massachusetts Ave. Cambridge, MA 02140 @spirersomes


#12
       I personally perceive plating to be the greatest
dishonesty of all (short of outright misrepresentation) 

I agree with you 100% Ron. This is almost as bad as the “claw
hiding the chip in the stone” that I mentioned. I recently was
asked to do a minor repair on what was supposed to be an 18K
white gold ring. To my horror as I was working, the surface
colour came off and I was left with a murky gray/white colour.
Fortunately I had the presence of mind to stop work immediately
and call the customer. I showed the ring to him and told him
that I could replate it, but that I strongly recommended that he
go back to where he had purchased the ring and get his money
back (or at least get a real good explanation). As of this
writing I do not know how he made out, but to me this is real
close to fraud (now that I think of it I should have tested for
the karat content, guess I am getting old and the brain cells
are starting to go a bit). B Goodman


#13

I have found in my own practice that the words perfect and
casting hardly go together. Very little in nature is perfect,
other than the design of nature itself. If a person attempts to
close holes and pits caused by porosity in metal castings are
they trying to hide something, or are they trying to correct
something? Who is to say what another individual’s intention is?
Aren’t those who are treating, filling, dyeing, lasering,
whitening, and otherwise enhancing gemstones working towards
this same premise?

I, for one, believe that most professional (I emphasize the term
PROFESSIONAL) goldsmiths/jewelry artists/ jewelers/whatever, have
their own individual criteria to determine when an object is
viable, and when an object needs to be remade or recast. Leave
it up to them to decide and they will offer you the same
consideration in your own studio.

Respectfully,
Michael David Sturlin, jewelry artist @Michael_Sturlin


Michael Sturlin Studio, Scottsdale Arizona USA


#14

Aptly put, Ron; I agree with your take on plating jewelry, and
might add, it burdens the jeweler and subsequent jewelers who
try to work on a piece with the need to continue re-plating.
There are cases where plating doesn’t bother me. If the piece
is an art work piece, where plating is a coloration process
pertinent to the image of the piece, that’s a different use of
plating in my opinion. Of course, it goes without saying that
these kinds of articles are handled differently and the
expectations surrounding durability are adjusted accordingly. I
would hope price in these cases, also was representative of
artistic merit and not some of the typical craftsperson’s
concerns for practicality. In other words, some things are just
made more to look at than wear, and if plating is part of the
"picture" of the work, it’s an obviously different application
of plating. But rhodium over white gold, 24K over 14 yellow,
yep, it’s phony and I don’t know why some of us have gotten used
to it (yes I do, but I don’t want to start ranting about
"merchandiser’s mentality" again).


#15

Pedro, would you be generous enough to share your knowledge in
getting perfect casting ? For the majority, pinholes seems to be
part of casting. We all would be appreciative to know how. Thanking
you in advance.


#16

I once worked for someone who’s castings more than occasionally
resembled swiss cheese.I filled the larger holes with tiny beaded up
pieces of gold. Sometimes I burnished or hammered them in, or just
lumped them over the problem area, then “sweated” them with my torch
so that they would pool up and drop into the holes. …Sort of low
tech compared to laser welding, but I didn’t need to use any solder.
By applying enough concentrated heat with a very small intense flame,
the surface metal would start to boil up and meld the beads in place.
. After that I filed it smooth or used an abrasive wheel to
re-establish the design.This treatment was, of course effective
primarily on shanks or places that didn’t have extremely fine
detail… I’m not sure if this method has already been mentioned…What
do people think of it? I The structural integrity of the piece
remained intact… if the porosity was deep and pervasive, I did not
try to salvage the piece.

Jesse Kaufman

@Jesse_Kaufman


#17

B, I work on hundreds of 10,14,18k white gold and yellow gold rings a
year.I would say 90% of all the white gold rings that pass in and out
of my shop are plated by the vendor with a flash plating of rhodium as
are chains S.S. and white gold.Many 14k yellow chains are flash plated
by the vendor in various degrees of yellow to make them look richer as
in 18k because the market most chain manufacturers are serving is
worldwide where as in some European countries 18k is the jewelry of
choice.Why plate white gold?It has nickel in it and tends to(depending
on the alloy)have a yellow tinge under certain lighting
conditions.What is white gold anyway but a psuedomorph for the masses
designed to replace that noble metal platinum which scratches to a
dull gray after a short time on the finger of even the most inactive
human.So if it wasn’t for that ridiculous world war they had.We might
not even have to deal with white gold but I do believe that we would
have to deal with plating.I went to a Sante Fe symposium and I seem to
recall a paper on chemical deposition by ancient south American
tribes.Gold vermeil been around a long time.Deception?The vendor or
artists or manufacturers that plate white gold range from the top of
the heap down to the independents.If I take a silver ring and plate it
in gold and sell it as solid 14k .That is deception.I don’t really
like having to buff off rhodium and have to replate the ring but hey I
get paid to do it.It’s part of the gig and I haven’t had a customer
ever say they have been taken after I tell them I have to replate
their ring with rhodium.Which by the way is way more expensive than
gold or platinum(Lately)If we have to put tags on rings stating they
have been flash plated with rhodium then we better start tagging every
ring with a treated stone or pearls that are dyed.For some reason I
can’t see the sales associate at Tiffany’s telling a customer as they
are walking out.Oh by the way did I mention that the tanzanites in
your $30,000 tiara were root beer brown just last week until we
torched them.Just my copper clad two cents worth Best J Morley Coyote
Ridge Studio Where it is Brrr-


#18

All, I went to a lecture on porosity that was part of the Sante Fe
symposium years back and the way I understand and have seen porosity
is that there are two major types of porosity.Micro porosity and macro
porosity.Macro are large pits or can be tears in the metal or the
dreaded spongy looking stuff that can take up much of the
casting.Macro porosity can be fixed in some instances by removing the
section of the ring and replacing it with a new section of gold.Micro
porosity tends to be in isolated spots or may be rampant in the
casting and can be microscopic or be seen by the naked eye.They can be
subsurface or surface defects.They tend to be caused due to shrinkage
of the metal as it cools.Thick top sections of say a gents signet ring
will cool slower than the thinner shank section.This causes tears in
the metal which can be Macro or micro.There are other types of
porosity such as carbon inclusions or gas inclusions.There are also
occlusions ,surface deformation and a whole slew of casting defects
that can occur due to a whole slew of variables.Given the fact that
porosity can be microscopic in nature or subsurface I find it
incredulous that some casters would contend that they never get
porosity.Just my porous thought on the matter.J Morley Coyote Ridge
Studio Where you can feel fall closin in


#19

Dear Fixers, As a caster of 25 years I have been watching this thread
on “fixing” porosity with great interest. I have a favorite burnishing
tool made from a hex head bolt that has been polished. It works great,
but alas, it doesn’t get used very much at all. A full 95% of porosity
is due to improper spruing. I had a customer give me a wax to cast
last year sprued the way he thought proper. He didn’t want me to
re-sprue it because he didn’t want to incur the extra cost. I told him
that the ring might get porosity in it, but he felt confident and said
to proceed. It did indeed have a copious amount of porosity. He
thoughtfully photographed the ring and sent me a copy when he paid me
for my work 8 months later. The photograph is a cherished reminder of
the importance of knowledgeable spruing. A little burnishing from time
to time especially on very thick pieces is not uncommon, but should
not be a drastic amount of work and indeed should be almost rare. An
ad we ran for years had the by-line of “Taming of The Sprue” I think
I’ll re-use that ad. John, J.A.Henkel Co.,Inc. Moldmaking Casting
Finishing


#20

Daniel, Bully for you! Disclosure does sanctify the deception of
plating…for some. I would opt for getting it right the first time.
To each his own. As for the analogy of self-destruction of stones, I
would have to agree with you that most stones are doomed to oblivion
by virtue of the fact that jewelry design frequently does not take
into consideration the fact that most stones should be protected and,
certainly, the average customer is in a deep fog about physical
attributes of stones. Furthermore, many customers just don’t give a
damn; indeed, some seem dedicated to destroying their precious
posessions. ( There was a period in Middle Eastern History when
wealthy Sheiks abandoned their cars in the middle of the desert when
they ran out of gas !) In our own society, some ladies will go from
the jewelry store to their gardening chores without regard for
protecting or conserving their investment. Actually, with regard to
your destroyed two year old Tourmaline ring,we both know that our
conscientious customers can get a lifetime of use from same with
minor precautions. All it takes is an awareness of the limitations of
the physical properties of the stone and the metals. Every jeweller
owes it to his customer to educate same about the risks of wanton
usage…the customer can then do what he pleases without recourse
to
blaming the jeweller. And, oh yes, your comparing the wearing
characteristics of corundum to diamond is not valid. A solitaire
worn by an active person who does not take any precautions to protect
her jewelry can easily destroy a Ruby or Sapphire in a very short
period of time. Ron at Mills Gem, Los Osos, CA