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Flux and borax / alcohol

I have a question about the use of a flux as well as the
borax/alcohol. When is the flux applied? Is it before or after the
alcohol? If it is after the alcohol, is the alcohol burnt off first
or how is it done?


Larry, I have some borax in a jar covered with alcohol. I swirl the
piece in the mixture and then take it out, and lite it on fire. Im
very careful not to get flame around the jar, as it is highly
flammable! And you can hardly see the flame. Good luck and be

Chris Slater

Larry, Dip the piece in the alcohol/boric acid solution, burn it off,
dip it and burn it twice more. You should have a white forsting on
the metal and stone, if any. Then apply flux as usual.

Jerry in Kodiak

You are exactly right. First swish the piece to be soldered in the
boric acid/alcohol solution. Next, burn the alcohol off which will
melt the boric acid crystals across the surface of the metal. This
provides a thin protective coating almost like glass across the
surface of the metal. Then flux as needed to complete the soldering

Phillip Scott GG

I mix a couple teaspoons of Borax, and make it into a paste with
wood alcohol. The alcohol burns off much faster than water, so you
get less bubbling effect that can move your parts to be soldered
around. I don’t know if that helps you, but it works great for me.
Good luck, -Doug

When using boric acid ( you can find it at the local drug store in
the first aid department, powered boric acid) and alcohol as a flux
you dissolve the boric acid in the alcohol (I use a inch to 1 1/2 in
a 8 oz jar and fill it about 2/3 full with alcohol) you are looking
to create a super saturated solution so when the alcohol is burned
off it leaves a fine powder of boric acid. Make sure you use
denatured alcohol. I buy mine in the paint department of the local
hardware store. Alcohol sold as fuel will also work. Remember to have
a tight fitting lid on the solution as the alcohol will evaporate and
the boric acid will crystallize around the mouth of the jar and form
a crust if the solution evaporates down low enough.

Frank Goss

Hi Larry, I wish I had discovered this stuff earlier. Would have
improved my technical development and reduced frustration along the

First, the mixture is boric acid and denatured alcohol. This is
used as a dip, or brushed or dribbled on larger pieces or assemblies.
The boric acid doesn’t really dissolve, but is in suspension then the
bottle is shaken or stirred. After applying a decent coating, recap
the bottle and touch the piece with a flame to burn off the alcohol.
Be careful of flaming drops of the mixture (fireproof work surface,
of course). This process results in a fairly effective (but not
perfect) oxygen barrier to prevent firescale, especially on sterling
silver. Not necessary for fine silver or higher karat golds, except
maybe to preserve a finish.

Boric acid can be obtained, off the shelf, at larger and more
traditional drug stores. If you’re unable to locate it, usually in
the eye care section, don’t hesitate to ask the pharmacist to order
it for you. This also works for specialty items like glycerine and
wintergreen oil.

Okay, now you’re ready to solder. You might want to use your poker
to scrape the joint to be soldered to clean the boric acid powder
from the seam, although it has never really caused me a problem.
Apply flux to the joint, apply solder and fire it up as usual. Choice
of flux is a totally different thread… :wink:

All the best,
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)

Hello Orchidians, Thought I’d add a bit to Frank Goss’s excellent
description, and invite John Burgess’s input Re: the correct name.

<Remember to have a tight fitting lid on the solution as the alcohol
will evaporate and

    the boric acid will crystallize around the mouth of the jar
and form a crust if the solution evaporates down low enough. 
My gold-smithing mentor used to grip about having the jar lid

“seize up” from the boric acid crust. I happened to be fortunate
enough to be in the right place at the right time and obtained a few
short, wide- mouth glass bottles that had ground glass stoppers. (A
lab was discarding them.) I’d describe the containers as reagent
jars - at least that’s what we called them in chem lab decades ago.
Cut to the chase: they were perfect for the boric acid/alcohol
solution. The crust did form, but it was simple to pry gently
against the flared top of the stopper and release the top. Wide
mouth allowed dipping of larger items. Quick cover with the
stopper. Glass. My mentor was pleased; maybe (John, are they still
around?) you might try a reagent jar. Love this forum and thank you
Hanuman for all your hard work, Judy in Kansas

Recent refernece to flux started me thinking. Has anyone seen or
developed a reference or chart for the suitability and
charcteristics of various fluxes in certain applications? Such as,
“Flux B burns out at sustained high temps.” “Flux C only works for
short and fast, low temps, with easy solder”. “Flux G for gold but
not silver”, etc.

I was doing some IT soldering a few days ago, and it took 3 tries to
get it done. I could see that the flux (Griffith’s green stuff) was
burning off too soon. I went to my e-mail later, and lo! Saw that I
should have been using the Handy Flux. I have built up quite a
collection of various fluxes, but was never sure which ones had
specific applications. I have Borax (universal flux, gets used for
most things), Handy, Griffith’s, Black Flux (…don’t remember WHAT
I bought that for… steel?), and various others that are probably
other brands of those above.

If such a chart does not exist, does anyone feel like tackling this?
It would be so useful.

Sincerely, Lin

Pardon me for being repetetive. This story and it’s solution can be
found in the archives but I suspect with the normal flow of traffic
it will get no attention there.

First off, let me point out that I am a carefree and somewhat
careless individual. In years past I have used acids and other
poisons with abandone. When I was a kid, I made firecrackers that
today would be classified as bombs. My point is that I am not a
sissy-boy that scares easily. I don’t recommend my behaviour for
anyone else. None-the-less, I no longer use a mixture of boric acid
and alcohol. Let me explain

When I started out on the goldsmith’s bench, I was taught to use
boric acid to coat jewelry and protect it from oxygen during heating
operations. Alcohol was used as a carrier. Ignition of the alcohol
produces a fairly even distribution of the boric acid. One fine
morning I accidently I accidently ignited the jar of solution. In the
previous years this wasn’t a problem as all one needs to do to
extinguish the fire is to drop the lid on the jar. Unfortunately, I
had spilled a tiny, and let me emphasize, a tiny drop onto the back
of my hand. It too lit up. I very gingerly attempted to put the jar
down into my tray but along the way, I managed to bump into
something. The result was a bigger spill. The fire was confined to
my bench and oh, my hand and a little of my shirt. The burns to my
hand required at least seven, maybe nine months or so to heal. Deep
burns heal from the edges towards the center and not from inside out.

Since that experience, I have learned to use powdered boric acid
without the alcohol. Simple static and normally present oils allow
the boric acid powder to cling and provide a substantial coating
without the alcohol.

Bruce Holmgrain JACMBJ

Hi Larry, Am I correct in supposing that your question is about
protecting the polished surface of the jewellery when you need to
make a soldering repair or adjustment on the finished piece? If this
is so, I’ve had the best results from:

  1. preparing the solder join carefully so as not to mark too much of
    the surrounding polished surfaces, but making sure the soldering
    faces are bright and clean.

  2. place the flux and solder appropriately on the join.

  3. warm up the piece so that the flux dries on the join, holding the
    solder in place.

  4. only then do I apply the boracic-alcohol mix liberally over the
    rest of the piece, but make sure that it doesn’t flood too much over
    the area to be soldered.

  5. burn off the excess alcohol leaving a crust of boracic to protect
    the jewellery and solder the join as per usual.

I discovered that if too much boracic fused over the solder join as
I attempted to solder, it formed a glassy barrier to the melting
solder, sealing it off from running into the join as one would have
expected. Kind regards, Rex Steele Merten

I’ve had the same problem with crust. What works beautifully is a
plastic cosmetic cream jar. It’s about three inches across and three
inches deep. It seals so beautifully that I never lose anything via evaporation.

You rang Madam? Yeah, g’day;

    short, wide- mouth glass bottles that had ground glass
stoppers.  (A lab was discarding them.)  I'd describe the
containers as reagent jars - at least that's what we called them in
chem lab decades ago. 

Actually I reckon the snappy catch answer to this is that we simply
called them “wide mouthed ground glass stoppered bottles.”

However, unless one is very familiar with ground glass stoppers it
might be as well to remember that these are very prone to freezing
up. For the really recalcitrant stoppers we had a special series of
techniques. If it didn’t come out with reasonable force, we gripped
it in one hand wrapped in a tea towel, holding the stopper tightly
and at the same time pushing it upwards, and gently tapped it with a
piece of wood, getting a little more fierce with the tapping, yet
hitting the centre of the stopper edge so as not to chip it. If this
didn’t work, one (very skilfully) rapidly exposed the neck of the
bottle to a very gentle flame, working all around it. The idea is
to cause the neck to expand and so loosen the stopper. If you don’t
like this; whilst rotating the bottle hold the neck under a stream
of warm water. Or another way is to make a single wrap of string
around the neck (of the bottle, silly) then pull the ends back and
forth and so as to heat the neck. Then try the tapping business
again. Finally, if the contents of the bottle are really valuable,
cut off the neck. Make a deep file mark in one place of the neck.
Get a piece of 8 - 10 gauge fencing wire and bend one end into a sort
of hook shape that fits neatly half way around the neck. Make this
hook red hot and rest the neck of the bottle in it, rotating
continuously. You will hear a click and a neat crack will follow
round the neck which will then come off cleanly. Now transfer the
bottle contents to a wide mouthed plastic screw top jar and screw the
top on tightly. If you want it to be really airtight, place a piece
of thin rubber in the screw top first.

I have used these techniques to open half gallon bottles of
concentrated acid. – Cheers for now,

John Burgess; @John_Burgess2 of Mapua Nelson NZ