Brazing Silver Soldering and Soft Soldering


The Importance of Safety
One of the most important aspect of soldering any project is to take the proper measures to safeguard your health. Soldering involves working with potentially hazardous materials like lead, flux and harmful fumes. By observing specific safety precautions and using informed common sense, soldering and brazing can be a safe. The following is intended to serve as a general rule of thumb. Since each person and situation is unique, you should use this information as a starting point to help you make informed safety decisions.

Solder only in a well ventilated area, and use an exhaust device that moves solder fumes away from your face.
If you don't exhaust to the outside, use a bench top fan or intake device with a replaceable smoke/fume absorber. It should draw solder fumes into the replaceable filter. The filter should be activated charcoal and designed to remove particles smaller than 1/2 micron from the air.

Most popular solders used in stained glass are lead based. When you are using them, follow these precautions:
Always thoroughly wash your hands after soldering.
Do not discard lead or solder scraps into the trash. Find a means or place to recycle them.
Never use lead based solders that will come in contact with food or children, or will be frequently handled.
If you are making jewellery or napkin holders, use lead free solder.

Soldering tools operate at high temperatures, so these safeguards are important:
Wear safety glasses! Solder and flux can "pop" and "spit."
Solder on a fire resistant surface. or dry wall are good .
Never leave your iron plugged in and unattended.
Never set your hot iron down on anything other than an iron stand.
Replace the cord of your iron if it becomes worn or gets burnt.
To prevent burning your fingers, use needle nose pliers or heat resistant gloves to hold small pieces.
Never cut off a grounding prong on an iron plug to make it fit an ungrounded receptacle.


Why Do We Use Solder?
Solder is a combination of tin and lead used to create a strong bond between other metals.
The Advantages of Solder

Some of the advantages of soldering versus other bonding methods are:
Solders are easy to use and relatively inexpensive.
Low energy is required to solder.
Properly soldered joints are highly reliable.
Solder joints are easy to rework or repair.
Experienced craftpersons can exercise a high degree of control over the soldering process.
Solder joints age very well. They can last for years, decades and centuries.

Types of Solder
Solders are usually a mixture (alloy) of tin and lead, designated by two numbers representing the percentages of each metal in that specific mix. The first number always refers to the percentage of tin, the second is the percentage of lead. The most commonly used solders are 60/40, (60% tin/40% lead) 50/50 and 63/37. "Lead-free" solders have no number designation and are a mixture of tin and small amounts of other metals.
An important term for solders is the "working range" or "pasty range." This is the range of temperature between which solder transitions from liquid back to solid.
Solders with a 63/37 or 60/40 composition are the most free-flowing kinds and are particularly good for working on delicate printed circuit boards. That is especially the case if you use solder in thin, 16 or 18 gauge wire form: avoid thicker solders which are difficult to control in terms of quantity and usually don't flow quickly enough.


Why Do We Use Flux?
Flux is a chemical compound that is used to promote the bonding of metals by removing the oxide residue simultaneously with the soldering process. Most metals left exposed to the air around us react with the air to form residue on the surface of the metal. The process is oxidisation and the residues are oxides. Each mix of metals being joined has a specific flux that best promotes this bonding process. In our subject, the metals being joined are primarily copper to tin/lead solder and lead, brass or zinc to tin/lead solder.

Characteristics of Fluxes
Liquid flux is the most widely used. It may or may not be water-soluble. Water-soluble fluxes clean up
very easily, but are thinner and some have a tendency to evaporate quickly and require repeat
applications. Some liquid fluxes are thinner than others and have a tendency to run or spread out from
their point of application.

Gel Flux is generally water-soluble and "adheres" well to the surface being soldered. Gels tend not to
evaporate as readily as liquid flux, but if you apply too much, they produce more "spitting" and "popping" as you solder.

Paste Flux is very thick, stays where it’s applied, and doesn't evaporate easily. It's effective when soldering 3-D forms such as lamps. Paste fluxes can be difficult to clean. Be very careful not to over apply a paste flux, as it will also spit and pop, leaving pits on your solder seams.

Getting the Most From Your Flux
It is important to keep your flux clean and free of impurities. This will ensure the purest possible solder joint. One way to keep your flux clean is to avoid dipping in and out of the original container. Pour out the amount you will need for your current project into a separate, smaller container. Don’t leave the flux bottle sitting around with the cover off. Never pour left over flux back into the original container. Fluxes often will produce fumes as you solder. Make sure you are aware of and follow the precautions
suggested in the health and safety section of this guide.

Brazing Silver Soldering and Soft Soldering
These three processes all have similarities when they are carried out. They all require the parts to be joined to be very clean before joining is attempted. They all require a flux (usually Borax in the case of brazing and silver soldering and Zinc Chloride or Resin in the case of soft soldering) which is a chemical that works to keep the joints clean whilst the job is being heated and to make the solder flow once it has melted. Soldering will not be successful if flux is not used. Brazing and silver soldering joints are heated using a gas torch. With these three processes the work itself is not melted. An solder is used to 'stick' the
pieces together. Welding requires the work piece to be melted.
Soft soldering done with the type of irons shown is weak in comparison to brazing and silver soldering. The most common materials, which are soft soldered, are copper, steel brass and tinplate.
The brazing torch is also used for silver soldering. It provides a strong joint. The solder for brazing is called spelter and is made largely of copper and zinc. Silver soldering spelter is largely silver copper and zinc. Main metals joined using these processes are steel copper (brazing), steel, copper brass for silver soldering.

Soft Soldering (approximate temperature 200 degrees C)
This is done with either an electric or gas heated soldering iron. The iron has a copper tip which carries
heat and solder from the gas/electric to the work surfaces. The soldering iron tip needs to be charged
with solder after heating this is done by dipping the iron tip into flux and melting solder onto it.

Stages in soft soldering

1 The joint must be clean and fit well together since soft solder does not fill gaps very well.
2 Place flux on the joint. (Active fluxes are better for most jobs as they provide a better final result but do give rise to corrosion after soldering and for this reason the joint should be well washed afterwards). (Passive fluxes are used in situations where the joint cannot be cleaned after soldering e.g. electrical work).
3 The surfaces to be joined are coated with a thin film of solder (called tinning) using a soldering iron.  The job has to be warm enough to allow the solder to flow from the soldering iron to the work surface.
4. After tinning the job is reheated with a clean soldering iron to melt the tinned surfaces together.  Wash the work if active flux has been used.

Brazing and Silver Soldering ( Temperature range - 625 to 875 degrees C)

Stages in Brazing/Silver Soldering

1 Joints need to be cleaned using emery or file.
2 Mix flux with water to obtain a look of melted ice cream.
3 Put flux on the joint and on the spelter.
4 Hold the joint in place with wire if necessary.
5 Heat the work to the correct temperature (625 degrees is dull red 875 degrees is orange/red).
6 Touch the spelter on the joint when BOTH pieces are hot enough, the flux will make the spelter flow.
7 Allow the joint to cool.

NB If both parts of the work are not equally hot the spelter will stick to the hottest part and the joint will not work.