German Micro Welding torch • Gas Cylinder Safety
Precision LP Gas Torch • Trouble shooting
Hard
soldering
(brazing) produces
a strong
joint of two metal
surfaces using heat and solder (a metal alloy), which flows into tiny spaces. Soldering
is a
complex technique, which requires careful planning, knowledge and
practice:
1.
Set up of solder station
2.
Flame
3.
Solder / Flux
4.
Preparation
5.
Procedure
6.
Pickling
7.
Trouble shooting
1.
Soldering station
for right-handed people:
On
left-hand side: German
Micro Welding Torch or Precision LP Gas Jewelers
Torch
In
the centre:
fire brick on
top of a large ceramic tile to safely absorb the heat from the torch flame
On
right
hand side:
required hand tools e.g.: flux, solder, lighter, water for quenching, tweezers,
soldering jigs (clamps), metal weight to hold soldering jig in place.
Below
working area:
Keep a cloth handy on a hook to dry quenched item. Flammable objects
should be
kept
away from solder station (you
can
create a fire brick barrier behind and on the sides)
2.
Flame
size
and adjustment depend on the size of objects and materials to be soldered.
Small
pieces require a smaller pointy flame.
When
soldering with Oxygen and Fuel Gas, keep in mind:
Preferred:
Neutral flame = slightly
reducing flame (pale blue) A strong reducing flame with a
bright yellow tip leaves a carbon deposit due to the lack of Oxygen and is not
desirable for
soldering.
Oxidizing flame:
hissing bright blue (use where intense heat on a small area is required or for
welding). It may
cause formation of oxides, which will hinder soldering!
Annealing requires a larger, softer flame with a slight yellow tip.
3.
Solders
are metal alloys different from the parent metal,
containing
other metals like zinc or cadmium to create a lower melting point.
There is a variety of solders available, silver solder for silver or copper,
gold solder for gold.....
Hard,
medium and easy solders are available as paste, wire or what
we
prefer: in thin
sheets, which
should be cut up into tiny pieces
using wire cutters or very sharp scissors.
The surface of oxidized solder should be cleaned,
if necessary use a wire brush,
a scraper or steel wool.
Hard solder
has the highest melting point and should always be the
solder of choice.
Try to use easy solder only
as the last resort or for repairs to avoid previously used
solder melting
again.
Melting
temperatures of different solders (liquidus):
Sterling Silver
Gold
Platinum
Extra Easy
643°C 18ct Yellow Easy
710°C Easy
1100°C
Easy
706°C 18ct Yellow medium 785°C
Medium 1250°C
Medium 732°C
18ct Yellow hard 841°C
Hard 1390°C
Hard
778°C 18ct White
hard 892°C
22ct
Yellow Gold
very hard 955°C
Lead-Tin
solders are soft solders for plumbers and contaminate Gold making it brittle. They should
never be used on Gold jewellery, not even for repair work.
Flux
=
Borax based
powder of
various compositions mixed with solvent (water or other). After evaporation of
solvent it deposits on metal, becomes liquid, takes up oxides and prevents
oxygen reacting with metal
(oxidisation).
4.
Preparation:
Spend some
thoughts about the location of the joint: stress point, future repairs (the
colour of solder could be visible or a bad joint obvious)
Ensure
a clean, grease free joint and solder.
To degrease the item can be
pickled
for a few minutes. Use
a pair of pliers or tweezers to take it out of the pickle.
Metal
ends need to fit together properly.
This often requires careful filing.
Difficult
assemblies can be supported or held in place by binding wire, clamps, pins or
tweezers.
5.Procedure:
In order
to prevent oxide coating (or fire-scale in silver = cuprous oxide or cuprite):
a.
flux
the joint
using a thin paint
brush
before and
again
while
heating until a white coating appears
b.
avoid heating the metal for too long
c.
flux
the solder by
picking up a piece of solder with tweezers, touching the flux brush and placing
it on
top of the hot, now sticky joint
d.
solder without hesitating – move the flame slowly over the object,
finishing in smaller
circles on
the solder spot, directing the molten solder:
the solder will follow the heat = the flame is drawing the solder through the
joint.
You see the solder
run with a flash of brightness
(capillary
action will suck it into the joint), then
remove the flame.
To
join
metals of unequal size
or thickness,
heat the
thicker side
first and it
needs more heat, otherwise the solder will stick to the thinner side.
To
observe the colour
(which indicates the temperature) and appearance of the metal remove light
source or shade the area.
Before quenching
in water,
check the joint for complete soldering, a continuous
bright line & if necessary reapply flux and resolder. A
successful solder
joint
looks shiny
on the surface and is visible on both sides. To achieve
the best results, experiment with flame size and distance to object.
Using tweezers or pliers, pick up the hot metal and immerse into a jar of water.
Dipping the item in Boric acid powder will form a protective layer on some gemstones and on polished gold (that reduces the effect of heat and oxygen on the metal surface).
6.
Pickling:
After
soldering
or if solder doesn’t flow,
pickle
in diluted sulphuric acid or substitute
(add 3 parts of acid to 10 parts of water. Always
add
acid
to
the water!)
A pyrex glass pot with lid is a good choice to keep your acid in, but cannot be
used for food preparation ever again.
Before pickling remove iron
binding wire to prevent accidental copper -
plating of the soldered items!
Use long stainless steel tweezers to carefully immerse a metal item into the pickle solution for about 10 minutes. Be careful not to drop it or splashes can eat holes into your clothes. Gloves, goggles and an apron offer good protection.
Rinse
in water thoroughly.
Dry
with cloth. Pickling is finished, when
all
flux glazing (flux
glazing will damage files) and oxide deposits are removed. I
prefer not to heat the pickle, but it takes a bit longer. Always
quench your
soldered item in cold or warm water
(some alloys in methylated spirit) before pickling.
Do not quench in ACID!
(Occupational Health & Safety OH & S)! Material Safety Data Sheets MSDS.
We keep our acid in a corner on the balcony to avoid harmful vapour
inhalation. To discard old pickling solution, when it is not working
satisfactorily any more, you can neutralize it with lime powder or baking soda.
Once it stops bubbling it is okay to pour into the garden.
7.Trouble shooting:
Scorching, melting or collapsing:
Too hot
flame or the same spot heated for
too long.
The
solder takes forever to melt or does not melt at all:
Not enough heat.
A
weak and visible joint:
Not enough
solder used.
A large
lump of solder forms:
too much solder
has been used.
Black oxide deposits
on the solder area prevent the solder from flowing, it could
be the result of:
-
not enough flux (or solder wasn’t fluxed),
-
overheating of metal or solder,
-
too much oxygen in the flame,
-
heat application for too long,
-
applying solder too early or too late.
Solder sticks to one side of the joint:
-
the seam is too large or
-
one side is hotter than the other or
-
the solder was not placed on top of the seam.
If
the solder jumps off:
preheat
the fluxed joint first.
Porosity
may be caused by
overheating
the lower - melting solder components like zinc and cadmium.
I would like to add a few
recommendations:
Most novice jewellers forget to preheat the glazed (seasoned) crucible to orange
glowing colour before adding the metal and additional borax powder. It is very
important for silver casting as the alloy is very reactive when molten (also
Silver/Copper crystals grow larger). Extended heating can result in cracks when
rolling therefore cast your metal without hesitation into the preheated ingot.
You should see a mirror like glow on the surface. Before casting move your
crucible around to make sure that there are no silver lumps hidden under the
surface. Silver can be reduced by rolling up to 50% before annealing again. If
you draw wire you need to anneal it earlier (when it starts breaking). Again:
keep your annealing time short and avoid too frequent annealing. Use the largest
possible flame for the job. Having
also
used
Hydrogen/Oxygen,
Acetylene/Oxygen and LP Gas/Oxygen I prefer to use a straight LP Gas torch
for silver work to reduce fire scale.
Only practice makes the expert.
All problems have a solution, no matter, how unique.
If there are alternative choices, pick the simplest one.
Accept mishaps as steps in learning this art. Take your time, enjoy, relax and try again.
Always be aware of your safety and the safety of others in your environment.
All cylinders should be considered and treated as full, regardless of their content. This means:
-
Read labels and Material Safety Data Sheet (MSDS) before use.
-
Store upright and use in well ventilated, level and secure areas away from pedestrian or vehicle thoroughfare.
-
Guard cylinders against being knocked violently or allowed to fall. All fuel and oxygen tanks must be either safely stored in an appropriate carrier or securely chained to a wall to reduce the risk of damage to the tank from being dropped causing possible explosion of compressed gases.
-
Always turn off main tank shut-off after daily use.
-
Hose should always be hanging down and held away from flame.
-
Always wear safety glasses when soldering, brazing or melting metals.
-
Wear safety shoes and gloves when handling cylinders.
-
Always move cylinders securely with an appropriate trolley.
-
Keep in a cool (not below 0°C), well ventilated, clean area on or above ground level. Ideally do not store in confined spaces or in front of emergency exits.
-
Keep away from artificial heat sources, sources of ignition and combustible materials, especially flammable gases (eg. flames or heaters).
-
Keep full and empty cylinders separate and toxic and corrosive gases separately from all other gases.
-
Keep oil and grease away from cylinders and valves.
-
Never use force when opening or closing valves.
-
Check for leaks by applying water with dishwashing liquid in it around all new connections
-
Don’t repaint or disguise markings and damage, if damaged return to supplier immediately.
-
People with a responsibility for storing or using gas cylinders should be trained and familiar with the procedures to be followed in case of an emergency.
-
Storage area layouts and emergency procedures should be carefully planned, recognising the possibility of an emergency arising.
-
Stores must clearly show signage in accordance with state Dangerous Goods regulations. This includes Class Diamonds, HAZCHEM, no smoking and naked flame warning signs.
-
Storage area should be designed to prevent unauthorized entry, to protect untrained people from hazards and guard cylinders from theft.
-
Use the correct regulator and flashback arrestors for oxygen and any fuel gas combination.
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