Safe and effective pickle and flux

Jewelry Discussion
#1

I have been following the in the Soldering Exercises
with interest because I am finally beginning to do some basic
silversmithing after more than 20 years making other types of
jewelry.

As I do all my work at home, I am interested in using the most
benign chemicals possible and bought borax for fluxing and alum for
making pickle. A couple of the messages raised questions that make me
wonder whether my concern for safety will make my work more
difficult.

One message advised the writer to use a modern flux not borax. Is
borax a problem? If so, why? And which of the many fluxes available
combines relative safety with effectiveness?

Most of the discussions on flux do not mention alum, although citric
acid is mentioned a few times, and it is probably also relatively
benign, most refer to Sparex or similar. From what I read this may
not be super-hazardous product, but it certainly isn’t all that safe
to have around either. So is alum a problem? If so, why? And is
Sparex really much much better? Why?

Thank you all for the great and advice.

Deni

North Carlton VIC
Australia

#2 
One message advised the writer to use a modern flux not borax. Is
borax a problem? If so, why? And which of the many fluxes
available combines relative safety with effectiveness?

All fluxes used on typical jewelry metals are based on borax and or
boric acid (borax is a salt of boric acid). They are the chemicals
that do the work of absorbing oxides from the metal surface. Other
chemicals are added to reduce the melting point, lower the
viscosity, assist in cleaning the metal, extend the temperature
range, reduce surface tension, etc. You can solder with borax alone
and if you are working in high karat yellow gold it will be good
enough. But other metals do much better if the flux becomes active at
lower temperatures than borax alone so you want one with something to
lower the melting point. The vast majority of silver solders along
with many karat gold solders melt at temperatures below the melting
point of pure borax which is 741C or 1365F.

If the flux it too viscous then you will have issues with the flux
inhibiting the flow of the solder because the solder cannot push the
flux out of the joint area, and so on. So while you can use borax
alone your soldering will be easier and more productive with more
complex formulas. The drawback is that many of the other chemicals
are more toxic and or corrosive etc.

Most of the discussions on flux do not mention alum, although
citric acid is mentioned a few times, and it is probably also
relatively benign, most refer to Sparex or similar. From what I
read this may not be super-hazardous product, but it certainly
isn't all that safe to have around either. So is alum a problem? If
so, why? And is Sparex really much much better? Why?

Citric acid is safer before use as pickle than alum or Sparax (sodium
bisulfate) as it is used in many foods and drinks to make them sour.
I would not drink alum or sodium bisulfate but almost every soft
drink contains citric acid. But after being used as pickle all of
them are toxic from the dissolved copper. You can also use lemon
juice or vinegar as pickle. The speed of the pickling action is the
main difference in the performance of any of them and of course the
smell in the case of vinegar and lemon juice. Sparax works faster
than the rest but most folks don’t see much difference when using
citric acid. I have never used alum but citric acid is much cheaper
than alum due to its large production for food uses.

Jim

James Binnion
James Binnion Metal Arts

#3

borax is just fine- most fluxes for jewelry are borax, or
hydrofluoric acid and borax, boric acid, or borax, boric acid and
disodium phosphate. the “new” fluxes are ceramic like substances in a
borax etc., base, but borax is a reliable indicator of temperature as
it clears when it reaches about 1400 F.Use it in confidence -
Cupronil is a good flux anti-firescale too - beast product out there,
and FAR more inexpensive than “firescoff” (there is a thread in the
archives should you want to read a lengthy discussion of firecoff’s
pro’s and con’s…

as for the pickle, pH down is the alternative to sparex without the
filler that Krohn adds that leaves a slick of brown clay on the top
of your fresh batch, though removed with paper toweling it’s
unnecessary and a hassle avoided by using the cheaper pH down on sale
now at the end of summer in home stores and x marts. sodium bisulfite
and cheaper than Sparex #2 for the same active ingredient. all the
other possibilities are discussed in the archives, sodium bisulfite
though works fastest around 114 F - the temp in a slow cooker on
low…save some money! use pH down and borax. borax can also be used
for refining, firecoat (when mixed with denatured / methyl alcohol

#4

You’re looking for products which combine relative safety with
effectiveness. It’s almost a contradiction in terms, because with
many substances in life, the more effective it is at its job, the
more hazardous it seems to be. The milder, safer alternatives, if
they do do the job, will usually do the job more slowly (talking of
pickle here, not flux), and the quicker-acting ones are generally the
more hazardous ones. However, as James Binnion pointed out, while
citric acid is a safe substance to begin with, it is rendered toxic
as soon as it has been used a a pickle, due to the dissolved copper.

Perhaps the best approach might be to take the middle ground with
something like pickle, and stick with the sodium bisulfate
alternatives (pH Down, pH Minus, Sparex, or plain sodium bisulfate
from lab supply which is what I use). It does the job really well
and quickly, but does not cause nasty burns if splashed onto the
skin, as something like sulfuric acid would do - obviously you’d wash
it off immediately in the event of a splash in any case.

Make sure it’s in a decent, safe container, and that it’s well out
of reach of children and pets, and follow any safety advice that goes
along with whatever chemical you choose.

Flux seems to be a more complicated issue, and it seems to be a
personal preference type of thing. You find a soldering regime which
works for you, but it may not work for someone else - and flux falls
into that.

If you’re soldering silver, you’ll want a firecoat as well as a
soldering flux. The firecoat protects the whole piece against
firestain while soldering, whilst the soldering flux, used at the
joint, keeps the oxygen away from the joint and the metal in that
area clean so that solder will flow into the joint. Some folks will
use two different fluxes for those two needs, whilst others find that
one flux will do both jobs. Personally, I use Prips flux and mix it
myself (the recipe is in the Orchid archives). Some folks find it to
be a good firecoat but not a good soldering flux - I find it works
fine for both jobs.

With regard to safety, some are obviously more benign than others,
but you should always take precautions when soldering to avoid
breathing in any harmful fumes. Prips seems to be a pretty safe but
effective flux as far as I can tell. I’ll be interested to hear what
others have to say.

Helen
UK
http://www.hillsgems.co.uk
http://helensgems.ganoksin.com/blogs/

#5 
borax is just fine- most fluxes for jewelry are borax, or
hydrofluoric acid and borax, boric acid, or borax, boric acid and
disodium phosphate.

Where the hell do you get this stuff? Hydrofluoric acid is not used
in flux. You really need to research your replies.

James Binnion
James Binnion Metal Arts

#6

I love the biodegradeable pickle from contenti as well as their flux.
It is a gel flux that most people hate but I love. Both are quite
safe!

#7

Fluxes do NOT contain HF. Some, especially paste ones do have some
fluorine compounds in the mix but then again so does my tooth paste
and the stuff dentists have been squirting on my teeth for many
decades. No Haz Mat shipping fees on even the nasty paste fluxes.
Buying HF these days is difficult for good reason.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

#8 
products which combine relative safety with effectiveness. It's
almost a contradiction in terms

First you need to define “safety”. Everything is relative. Here 's a
spectacular story I’ve waited for a reason to share here:

However, the dry ice bath embrittled the steel container wall,
which split while it was being maneuvered onto a dolly,
instantaneously releasing 907 kg (2,000 lb) of cold ClF3 liquid
onto the building floor. The ClF3 dissolved the 30 cm (12 inch)
thick concrete floor and another 90 cm (36 inches) of gravel
underneath the spill. The fumes that were generated (chlorine
trifluoride, hydrogen fluoride, chlorine, hydrogen chloride,
etc.) severely corroded everything that was exposed.3 One
eyewitness described the incident by stating, "The concrete was
on fire!"

Clark summarized it quite well also:

It is, of course, extremely toxic, but that's the least of the
problem. Itis hypergolic with every known fuel, and so rapidly
hypergolic that no ignition delay has ever been measured. It is
also hypergolic with such things as cloth, wood, and test
engineers, not to mention asbestos, sand, and water " with which
it reacts explosively. It can be kept in some of the ordinary
structural metals-steel, copper, aluminium, etc.-because of the
formation of a thin film of insoluble metal fluoride which
protects the bulk of the metal, just as the invisible coat of
oxide on aluminium keeps it from burning up in the atmosphere.
If, however, this coat is melted or scrubbed off, and has no
chance to reform, the operator is confronted with the problem of
coping with a metal-fluorine fire. For dealing with this
situation, I have always recommended a good pair of running
shoes."

Not something anybody here is going to be around, but it makes
extreme worry about Sparex a little silly, at least to me. In
Albuquerque we used to throw our soldering into a bucket of cold
Sparex, wait a bit and fish it out with our bare hands - rinsing
after, of course. I’m not promoting such behaviour, but it’s a fact
that we worked that way and my hands are just fine. Everything is
relative…

http://www.donivanandmaggiora.com

#9 
borax is just fine- most fluxes for jewelry are borax, or
hydrofluoric acid and borax, boric acid, or borax, boric acid and
disodium phosphate.

While some paste fluxes contain fluoride salts they definitely do
not contain hydrofluoric acid

James Binnion
James Binnion Metal Arts

#10

Deni,

Your email seems to mix up flux and pickle in a couple of sentences.
Flux is used on the metal you’re soldering. I like Handiflux paste
flux for soldering sterling and fine silver. It’s principal
ingredients are borax and boric acid. I use this rather than plain
borax because it’s already pre-mixed in a handy little jar and it’s
actually more readily available from jewelry suppliers and cost only
marginally more and I don’t have to mess with making it up.

For environmental considerations in your pickle (what you use to
clean your metal after you’ve finished soldering to remove flux,
soot, and modest amounts of cupric oxide) consider using citric
acid. You can often buy it in the canning section of your grocery
store. It’s the same citric acid as is in lemon-flavored powdered
drinks and is used throughout the food industry so it’s
toxicologically and environmentally benign. It takes a little more
time to clean things than Sparex and can be dumped down the sink when
you are done with it. I still prefer Sparex (actually I use dry pool
acid, which is the same thing, but often cheaper) and keep it warm on
the low setting of a crock pot when in use. I like it because it
works faster.

Denny Turner

#11

Hydroflouric (HF) acid is particularly dangerous and nasty. They only
place I’ve heard of it being used in jewelry work is in relation to
cleaning up platinum investment, and everyone I’ve ever spoken with
said they use methods that avoid the HF acid altogether.

Take a look at this website:
http://www.mnpoison.org/index.asp?pageID=151

Mike DeBurgh, GJG
Henderson, NV

#12

I use Citpic from Gesswein, its a citric acid pickle, seems to work
pretty good and doesn’t destroy clothes or burn your skin. Also Hard
Soldering Flux, the neon green/yellow stuff, also from Gesswein. This
stuff I like but not sure how “safe” it is, just don’t drink it :slight_smile: I
also cover my pieces in a borax acid/denatured alcohol mixure before
soldering. It works great at reducing firescale.

Best of Luck, Pete

#13

HF mixed with other rather nasty acids are really handy for titanium
work. I believe that there are less nasty options currently offered
by RMS. HF is damned nasty stuff.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

#14

To clarify - for the last time- I use minute quantities of it as
prepared in a self pickling flux intended for welding applications
from a German supply company…Not quarts of it in a vat in the
studio!. but a match head sized amount applied to a nonferrous metal
being joined to another nonferrous non precious metal to remove, or
rather prevent flux glass from forming, whilst the borax ( 93% of
the formula, the balance being ammonium chloride) works as the main
flux…What’s te big deal? everyone uses different fluxes for
different things, or so is my experience. I have at least 6
different flux types i use regularly and a borax cone i prefer over
all of them. or cupronil if I want anti-firescale prevention with the
flux and am too lazy to mix up my own alcohol and borax and DSP
combination!. If one reads the ingredients of Handy Flux for instance
there are at least 3 chemicals in it (Potassium Fluoborate, Potassium
tetraborate and Potassium Hydroxide - all salts of Potassium and
Boron) that make up their particular proprietary formula…I don’t
know of anyone using straight hydroflouric acid for anything other
than freon or refrigerants…but what i do know is it effectively
strips off enamel from any metal without damaging the substrate metal
and that is why I use the particular formulation I mentioned in a
list of common flux compounds…

By the way in re-reading my original post i initially made a typo and
meant hydrochloric acid. but would have thought most would have
realised the mistake as it’s such a common ingredient.

#15 
By the way in re-reading my original post i initially made a typo
and meant hydrochloric acid. but would have thought most would have
realised the mistake as it's such a common ingredient.

Possibly if you had been referring to soft (lead) soldering
hydrochloric acid would have been recognized as a flux component but
hard soldering or brazing fluxes don’t contain it. And it is not used
in modern soft soldering fluxes either having been replaced by the
safer zinc chloride, the zinc salt of hydrochloric acid.

James Binnion
James Binnion Metal Arts

#16

Thanks everybody for your and advice. As always, I
learned a lot from reading the replies to my question. Thanks too to
the people who assumed I didn’t understand the difference between
the functions of pickle and flux and undertook to explain them. I do
understand them, so any apparent confusion was in the writing of my
email for which I apologise.

My concern about safety isn’t about drinking the chemicals - I
wouldn’t drink my perfume or shoe polish or liquid soap either, but
I’m not worried about having them around. It was interesting though
that one person said he wouldn’t drink alum: I think we all are
drinking a certain amount of it, because it is the most common
chemical used in removing impurities from drinking water. And we are
eating it too - it is in baking powder and is used in pickles (the
edible kind) and maraschino cherries to keep them crisp. And it must
be reasonably safe for the skin because it is the main ingredient in
styptic pencils - the things used to stop bleeding from shaving
cream. So I felt OK from a safety perspective about using alum, but
was interested to know whether it would be less effective than
things like Sparex for pickling silver.

Some people mentioned citric acid as an alternative. I’m actually not
sure it is any safer than alum based on looking at the MSDS on both
of them. I’m not sure what strength it is used at in pickle; in
dilute solutions, citric acid is probably pretty safe but from the
MSDS, it sounds like pure citric acid can cause quite nasty burns.
The MSDS says: “Hazardous in case of eye contact (irritant), of
inhalation (lung irritant). Slightly hazardous in case of skin
contact (irritant, sensitizer), of ingestion. The amount of tissue
damage depends on length of contact. Eye contact can result in
corneal damage or blindness. Skin contact can produce inflammation
and blistering. Severe over-exposure can produce lung damage,
choking, unconsciousness or death.” But the MSDS on alum is also
worrying, so probably caution is required with any of the options.

So I’ll need to go through the replies carefully because I’m not
sure you all have the same opinion, then decide whether for
effectiveness I should be using different products than the ones I
originally decided on for safety reasons. Lots to learn. The replies
also raised a new issue I hadn’t thought about - disposal of used
pickle - but I seem to recall this previously being discussed on this
forum, so I look up the archives. It also raised another issue, which
I will ask in a separate thread.

Thanks again
Deni

Deni Greene
North Carlton VIC 3054
Australia