Soldering hints, Trouble shooting & Gas Safety Advice

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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. Photos of reducing flame on this page, more photos on the main Torch pages.

 

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
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).


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.

 

Gas Cylinder Safety

 

    1. All cylinders should be considered and treated as full, regardless of their content. This means:
    2. Read labels and Material Safety Data Sheet (MSDS) before use.
    3. Store upright and use in well ventilated, level and secure areas away from pedestrian or vehicle thoroughfare.
    4. 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.
    5. Always turn off main tank shut-off after daily use.
    6. Hose should always be hanging down and held away from flame.
    7. Always wear safety glasses when soldering, brazing or melting metals.
    8. Wear safety shoes and gloves when handling cylinders.
    9. Always move cylinders securely with an appropriate trolley.
    10. 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.
    11. Keep away from artificial heat sources, sources of ignition and combustible materials, especially flammable gases (eg. flames or heaters).
    12. Keep full and empty cylinders separate and toxic and corrosive gases separately from all other gases.
    13. Keep oil and grease away from cylinders and valves.
    14. Never use force when opening or closing valves.
    15. Check for leaks by applying water with dishwashing liquid in it around all new connections
    16. Don’t repaint or disguise markings and damage, if damaged return to supplier immediately.
    17. 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.
    18. Storage area layouts and emergency procedures should be carefully planned, recognising the possibility of an emergency arising.
    19. Stores must clearly show signage in accordance with state Dangerous Goods regulations. This includes Class Diamonds, HAZCHEM, no smoking and naked flame warning signs.
    20. Storage area should be designed to prevent unauthorized entry, to protect untrained people from hazards and guard cylinders from theft.
    21. Use the correct regulator and flashback arrestors for oxygen and any fuel gas combination.
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