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Fire Scale


#1

Ive been making jewelry for a long time and most of it is in .950 silver,
over the time we’ve tried everything from coatings while soldering ,
to soldering with low amounts of oxigen in the flames ,
to sanding
to acid stripping and at the end a combination of all works most of the
time never the less it is far from perfect and every now and then an awful
stain does occur in the piece you need to ship tomorrow !
I wonder if some one has come up with something new lately ( not Argentium
or similars since they are not available here in Mexico)
some sort of selective electrostripping ?
or a chemical that only etches on the stain?

Com on people all of us together must have a solution , among this group
are the smartest and the most experienced , and this is a very old problem
, and ive seen so many antiques with a lot of detail
that are black from time but under that there is no " Firestain" only
patina from time .


#2

Dear Yves,

Soldering is not only melting an alloy to connect different parts.
I’m not saying that I’m an expert but I spend a lot of time figuring out what good soldering procedure is.
I made horrable looking solderjoints before I study what I was doing wrong.

Many of us wrote good articles how to perform a good solderjoin.
There are some facts one have to take care of like close fitting, clean metal, good solder etc.
The best way to produce a clean workpiece is learn how to communicate with your torch and workpiece.
They give you signs how stupid this may look like but they do.

Whatch how your workpiece changes colors, when your flux is melting, when your flux is changing color from brown to clear. Start with a reduced flame, learn how to take benefit from gravity because melted metal will run to the lowest AND hottest point. Know the melting point of your solder and your flux. Know the temperature window where you have to work with. Stay within this window of approx 30 - 40°C depending on the solder you use.

Observe when you need to apply more flux because flux will evaporate leaving a gap for oxygen to access the silver.
Don’t focus at your silversolder. When all basics are good it will flow You can’t help it run better by looking at it. Don’t tak you flame of your workpiece in order to reduce the temperature but move backwards holding the flame on your workpiece. This is called temperature controle. Taking i away from you workpiece is a free window for oxygen to access your workpiece.

It’s all simple basic stuff, there are no secrets other then covering your piece with a coat made by borax and boric acid.
Check out the melting temperature of both an d compare it with the soldering melting temperature.
The very best advice I can give is P R A C T I C E, over and over again. Learn from you mistakes and never give up.
After a period of time it becomes second nature like breathing because you understand what is happening and how to overcome firestain.

Forget about electrostripping and learn what firestain is, how it’s build, where it’s build and how it evaluates in a next heating.
If you do, then you’ll know that elctrostripping can’t help you out for several reasons.

Silversmithing is a way more difficult then goldsmithing because copper and silver are both metals with an attitude.

Another advice I like to give is to use hard solder.
I don’t use medium, easy or very easy except for repairs.
Yes I know, others have their opinion and swear by using them.
Know one thing. Lower solders have more yellow color due to the use of more brass talking about regular solder.
They will tarnish faster and you will see colorchange.

Sorry for this very long message.
Learning how to solder perfectly takes time, practice and lots of knowledge.

Wishing you al the best.


#3

you might see my post about a sterling silver fork left in the pickle.


#4

In Heikki Seppa’s book, Form Emphasis for Metalsmiths, he talks about sprinkling charcoal powder over a piece that’s going to be soldered. I haven’t tried this technique yet, but it makes sense.

I periodically sand down my hard charcoal blocks to keep their surfaces flat, and I have been saving the resultant powder for the time when I finally experiment with Seppa’s approach.


#5

Good luck with sprinkling charcoal powder on a piece that will be soldered.
The slightest air of gasstream will blow that powder of in a second
covering your workarea and everything up and around it with charcoal.
To me, it makes no sense at all.

Happy cleaning afterwards!


#6

Your comment makes no sense. Sprinkling charcoal dust on wet flux stays where it’s put. I’ve not observed it to make much of a difference but it does work.


#7

I will ask the obvious question. Are you using a protection solution of borax and alcohol and are you using a paste type flux? What type of torch and what gases?
I will disagree with the person that only uses hard solder. I work through a progression of solders from hard to easy depending on how many solder joints i am putting in a piece. I am sorry that you can’t get some of the new alloys because they solve all the problems you are having. Stuller sells sterlium which is my current favorite and I know they ship internationally.


#8

I’m curious about this. What is the charcoal supposed to do? I’m not as experienced as most of the people on this forum, but I was taught that one of the keys for successful soldering is to clean both pieces as well as the solder. Charcoal would seem to defeat that.


#9

I believe the theory is charcoal absorbs any free oxygen around the piece through burning the carbon and producing CO2 (and CO, so make sure your studio is well ventilated).


#10

Charcoal creates a reducing atmosphere, and lowers the oxygen (thus,
fewer oxides). Much the same logic as soldering on a charcoal, block, I
suppose. Never tried that trick, but that would be the mechanism (if it
works).


#11

I don’t understand why you can’t just order Argentium or Continuum and have it mailed to you in Mexico.

Is there a very high tariff on importing metals or something?


#12

Mexico is a big silver producer so importing silver to Mexico is sort of
unpractical tax wise and plus shipping fees make it out of the question
plus refining scrap costs are over the top here all workshops here do there
alloy in house and most shops just reuse scraps by adding fresh alloyed
metal ( mainly sterling .925 coper alloys) .
I have not worked with Argentium but I understand that it cant be remelted
without loosing its magical properties , ( this I dont know for sure since
I haven’t used it)
as for the charcoal I agree it helps a lot as well as fluxing and using a
reducing flame , and depletion gilding works marvels on my sheet prior to
manufacturing , Still im curious if any other tips will come from this big
family of modern day alchemists from around the globe .

thank you all , and still waiting for a new and surprising never heard tip
.

and for any member willing to come to Tepoztlan my shop is you’re shop !