Solder Alloys, 2

This is an updated version of a table on various possibly useful solders.

Solder Alloy	Composition	Solidus	Liquidus	Uses
25/75	Sn/Pb	183C	266C	general plumbing, car radiators
30/70	Sn/Pb	183C	256C	general plumbing, car radiators
30/50/20	Sn/Pb/Zn	177C	288C	economical solder for aluminium, Zinc and Cast iron
40/60	Sn/Pb	183C	238C	brass, plumbing, car radiators
50/50	Sn/Pb	183C	216C	general purpose, plumbing, not for gold, silver
50/48.5/1.5	Sn/Pb/Cu	183C	215C	reduces copper erosion on irons
60/40	Sn/Pb	183C	190C	electronics, good wetting, duller surface than 63/37
63/37	Sn/Pb	183C	183C	eutetic, electronics, stainless steel, bright joints
62/37/1	Sn/Pb/Cu	183C	183C	similar to 63/37 and reduces erosion on irons
90/10	Sn/Pb	183C	213C
95/5	Sn/Pb	238C	238C	plumbing and heating
96.5/3/0.5	Sn/Ag/Cu	217C	220C	recommended lead free for electronics
95.8/3.5/0.7	Sn/Ag/Cu	217C	218C	wave and dip soldering
95.6/3.5/0.9	Sn/Ag/Cu	217C	217C	eutectic
95.5/3.8/0.7	Sn/Ag/Cu	217C	217C	European preference for wave and dip soldering
96.5/3.5	Sn/Ag	221C	221C	wide use, poor wetting, strong lead free joints, stainless steel
95/5	Sn/Ag	221C	254C	strong, ductile joints on copper, stainless steel
94/6	Sn/Ag	221C	279C	strong, ductile joints on copper, stainless steel
93/7	Sn/Ag	221C	302C	strong, ductile joints on copper, stainless steel

Ag = Silver
Cd = Cadmium
Cu =Copper
PB = Lead
Sn = Tin
Sb = Antimony

Common stained glass solder compositions

Cementing Brushes

image credit: stainedglasscraft.co.uk

Use stiff, but not hard bristle brushes for cementing. Nylon scrubbing brushes have a good stiffness without being too hard. Some natural bristle brushes are very hard and scratch the came excessively. In general, moderately stiff brushes with about 1 1/2" bristles are fine for cementing. There should be space between the bristle bunches to aid cleaning.  As they do not last very long, they should be cheap, but with firmly attached bristle bunches.

Cleaning the brushes is very simple. The action of rubbing the cement under the leads with whiting causes a natural cleaning action to take place. As the bristles flex back and forward over the came, the cement is forced upward toward the handle, and then outward between the bristle bunches. Only a little effort is required to finish the cleaning: push a rounded stick between the bunches to move out the remaining cement. You now have a clean brush for the next job.

The alternative is keeping the brush in water, but this presents the problem of getting rid of the water (oil and water do not mix) before beginning to cement. As the water will emulsify with the linseed oil, it will be carried into the putty, leaving gaps in the cement when the water eventually evaporates. The cement will eventually harden, even though in water, as linseed oil cures by creating an organic polymer through oxidisation. It can also rot the wood handles.

Keeping the brush in mineral spirits does keep the brush flexible but requires drying/evaporating the spirit before beginning the cementing to avoid the residue of the spirit creating cement that is too thin at the start. This can be a really messy problem!

If you choose the “dry” method, it is important to keep the brushes free of hardened cement as it will scratch the leads badly, if not the glass too. Most brushes will only last 5-10 uses, and as they are not expensive, should be easy to throw away.

Melting Points of Solders

Common solders for stained glass are mixtures of tin and lead, respectively:

• 63/37: melts at 183°C (362°F)
• 60/40: melts between 183°C (362°F) and 188°C (376°F)
• 50/50: melts between 183°C (362°F) and 212°C (421°F)
• 40/60: melts between 183°C (362°F) and 234°C (454°F)
• lead-free solder (useful in jewellery, eating containers, and other environmental uses): melts between 118°C (245°F) and 220°C (428°F), depending on composition.

The 63/37 and 60/40 solders are most often used in copper foil work because of their smaller melting range. This allows the solder to set more quickly than the solders with higher lead content. They tend to give smoother beads also.

50/50 and 40/60 solders are more often used in leaded panel work. Their wider range of melting temperatures allows the solder to spread and become flat.

Other information on solders:

https://glasstips.blogspot.com/2015/07/physical-characteristics-of-solder.html

https://glasstips.blogspot.com/2018/02/lead-free-solder.html

https://glasstips.blogspot.com/2010/01/soldering-ingredients-and-methods.html

https://glasstips.blogspot.com/2015/07/lead-free-solder.html

https://glasstips.blogspot.com/2009/03/solder-alloys-1.html

https://glasstips.blogspot.com/2009/03/solder-alloys-2.html

Lead Light Cement

You can make your own lead light cement as the materials are fairly common and safe to use.  I have altered the original recipe through experience.  Too much of mineral spirits dries out the mix so quickly that the linseed oil cracks early in its life.  This results in the possibility of water leaking through the cracked cement.  One third or less of the dryer (mineral spirits) reduces the chance of too rapid drying.  I no longer use a drier at all.  This is my modified recipe.

Recipe
7 parts whiting/chalk
2 parts boiled linseed oil
(measured by volume)
1-2 Tablespoons colorant
This can be lamp black (carbon), black poster paint, concrete colorant powders, or black oil paint in sufficient quantity to give a black or dark gray colour to the otherwise off-white colour of the whiting and linseed oil.  

Do not use water based colorants, such as acrylic paint.  This does not mix with the linseed oil. Instead it forms a collodial mixture that interrupts the formation of the long linseed molecular chains that make it so good as a long term sealant.

The mixed leaded light cement

Method
Add the whiting (reserving about one quarter) to the linseed oil. Mix this well, by hand or with a domestic mixer capable of mixing bread dough. When these are mixed thoroughly, check the consistency. It should be like molasses on a cold morning - barely fluid.  At this point, add the colorant, so you will know the current colour and can adjust to make it darker.

Add more whiting as required to get the consistency you want. Experiment a little to find what suits you best. If you have to deliver the panel quickly, for example, you need to increase the proportion of whiting to make it stiffer. 

Comment
You should make only what you will be using on the current project, as the whiting separates from the linseed oil and sinks to the bottom in only a few days. The commercial cements have emulsifiers to keep the whiting from settling and so extend the life of the product. Since making your own is cheap and quick to make, there is no saving in making a lot.


Lead light cement is a simple, inexpensive sealant for leaded glass that you can make for yourself.

The Purpose of Flux

The primary purpose of flux is to prevent oxidation of the base and filler materials in the short time between cleaning and soldering. Tin-lead solder, for example, attaches very well to copper, but poorly to the various oxides of copper that form quickly at soldering temperatures. This applies to lead and brass too.

Flux is a substance that is nearly inert at room temperature, but it becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in soldering processes for lead, copper and brass.

Without flux the solder does not firmly attach to the lead or copper foil and often forms sharp peaks.


See also
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes

Soldering fluxes

Flux

Flux is a material that provides a “wetting” action between the metal (lead or copper in our case) and the solder.


There are various types of flux. Some are of more use in some circumstances than others. Among them are:

Tallow
This normally comes in a candle-like stick. It is made from rendered animal fat. Although this may put some vegetarians off, it is one of the best fluxes for leaded glass work and will work for copper foil, but is not generally preferred.  It is relatively natural, does not contain chemicals, and does not require re-application if left for a while. Over generous application does not produce any problems during the soldering. It just leaves more solidified tallow to clean after soldering. The cleaning normally requires a mild abrasive such as a brass or fibreglass brush to get the cooled tallow off the piece.

 




Oleic acid and other safety fluxes
Many of the safety fluxes are made of oleic acid (sometimes called stearin oil). These fluxes do not produce chemical fumes in the soldering process. They are easy to clean up with detergents and warm water. Safety fluxes require re-application if left to dry, as they are only effective while wet. Putting too much on leads to boiling off the liquid, making holes in the solder joint or line.

An example only.  There are many water soluble paste fluxes available

Chemical Paste fluxes
These fluxes come in a variety of compositions. You need to be careful about choosing, as some are very difficult to clean off the glass or solder line or joint. They do produce chemical fumes, so a fume mask is advisable while using this kind of flux. The paste does not require re-application if left, so the whole piece can be fluxed at once.

Acid fluxes
Acid fluxes such as the kind that is in the core of plumbers solder are intended to clean the joint at the same time as acting as the wetting agent. These are not recommended for stained glass work as they can affect the glass surfaces, especially irridised glass. They do produce fumes that require the user to have on a fume mask while soldering. The ease of cleaning relates to the particular composition of the flux, so testing samples is required before application.

See also:
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes
Soldering fluxes

Leading acute angles

Most of us like flowing lines in leaded glass windows, but these often give very acute angles to be leaded up. One way is to avoid creating intersections by using passing cames.  

But, if the cartoon does not allow for passing cames in acute joints, you have to consider how to cut the came to butt well against the next came. The easiest, but most time-consuming method is as follows:

Determine what the length of the came must be to reach the end of the joint.

Mark your lead there.

Determine what the shortest part of the came will be at the joint and make a faint mark there too.

Cut the came at the first (longest) mark.

Use your lead dykes to cut the heart out of the lead, leaving only the flanges. This is done from the end to just beyond the faint mark you made to indicate the shortest part of the joint.

You then need to smooth the two flanges where the heart was. You can use a fid or your lead knife to draw over the rough interior of the flanges. This enables the flange to be inserted below the came already in place, or to slide the new came over the modified came.

You can trim the upper came flanges immediately to conform to the angle of the joint or do it when the whole panel is leaded. Make a mark with a nail or your lead knife along the edge of the un-modified came. Then raise the flange and use your lead dykes to cut the flange along the line. Fold the flange down to butt against the passing lead and it is ready to solder.

Composition of Glass

Glass can do most anything. From bottles to spacecraft windows, glass products include three types of materials:

• Formers are the basic ingredients. Any chemical compound that can be melted and cooled into a glass is a former. (With enough heat, 100% of the earth's crust could be made into glass.)
• Fluxes help formers to melt at lower temperatures.
• Stabilisers combine with formers and fluxes to keep the finished glass from dissolving, crumbling, or falling apart.

Chemical composition determines what a glass can do. There are many thousands of glass compositions and new ones are being developed every day.

Formers
Most commercial glass is made with sand that contains the most common former, Silica. Other formers include:

• Anhydrous Boric Acid
• Anhydrous Phosphoric Acid

Fluxes
But melting sand by itself is too expensive because of the high temperatures required (about 1850°C, or 3360°F). So fluxes are required. Fluxes let the former melt more readily and at lower temperatures (1300°C, or 2370°F). These include:

• Soda Ash
• Potash
• Lithium Carbonate

Stabilisers
Fluxes also make the glass chemically unstable, liable to dissolve in water or form unwanted crystals. So stabilizers need to be added. Stabilisers are added to make the glass uniform and keep its special structure intact. These include:

• Limestone
• Litharge
• Alumina
• Magnesia
• Barium Carbonate
• Strontium Carbonate
• Zinc Oxide
• Zirconia

Based on an article from the Corning Museum of Glass

Lead Free Solders

Lead free solders have been created in response to concerns about lead, especially in the electronics industry. The following tables present a selection of available solder compositions.  The characteristics of these lead free solders can be compared to the common lead bearing solders in the last table.

Abbreviations for the metals of the compositions:

Ag=Silver; Bi=Bismuth; Cu=Copper; Ge=Germanium; In=Indium;

Sb=Antimony; Sn=Tin; Zn=Zinc

Melting Temperatures of Lead-Free Solders

Alloy  %                     Melting Temperature    Comments

Range (ºC)

Sn 65, Ag 25                         233           High strength; patented by Motorola (“Alloy J”)

Sn 99.3, Cu 0.7                     227           Eutectic

Sn 96.5, Ag 3.5                     221           Eutectic. Excellent strength and wetting

Sn 98, Ag 2                          221 – 226

Sn 77.2, Ag 2.8, In 20           175 – 186

Sn 95, Sb5                           232 – 240 Good high-temperature shear strength

Sn 42, Bi 58                         138           Well established; expensive

Sn 91, Zn 9                          199   Eutectic. Corrodes easily; high dross

Sn 95.5, Ag 0.5, Cu 4            217 – 350 Lead-free plumbing solder

Sn 97.25, Ag 2, Cu 0.75        217 – 219

Sn 91.8 Ag 3.2, Cu 0.5          217 – 218

Sn 95.5, Ag 3.8, Cu .07         217 – 220

Sn 95.5, Ag 4, Cu 0.5            217 – 225

Sn 95, Ag 4, Cu 1                 217 – 220

Sn 94.6, Ag 4.7, Cu 1.7         217 – 244

Sn 89, Zn 8, Bi 3                   192 – 197

Sn 97, Ag 0.2, Cu 2, Sb 0.8    287 – 318  High melting range; “Aquabond”

Sn 96.2, Ag 2.5, Cu 0.8, Sb 0.5      217 – 225

Sn 90.5, Ag 2, Bi 7.5             190 – 216

Sn-91.8, Ag 3.4, Bi 4.8          201 – 205

Sn 93.5, Ag 3.5, Bi 3             208 – 217

Sn 94.25, Ag 2, Bi 3, Cu 0.75   205 – 217

Sn90.7, Ag3.5, Bi 5, Cu 0.7     198 – 213

Sn 93.4, Ag 2, Bi 4, Cu 0.5, Ge 0.1         202 – 217

Sn 42.9, Bi 57, Ag 0.1           138 – 140

Sn 48, In 52                         118           Eutectic. Lowest melting point. Expensive

Source:

http://www.msed.nist.gov/solder/NIST_LeadfreeSolder_v4.pdf

Liquidus Temperatures (°C) of Candidate Lead-Free Solder Alloys for Replacing Eutectic Tin-Lead Solder

Alloy Composition%     Liquidus             Melting Range

98Sn-2Ag                                             221-226

96.5Sn-3.5Ag              221                    221

99.3Sn-0.7Cu              227                    227

96.3Sn-3.2Ag-0.5Cu     218                   217-218

95.5Sn-3.8Ag-0.7Cu     210                   217-210

95.5Sn-4.0Ag-0.5Cu                             217-219

95Sn-5Sb                                            232-240

42Sn-58Bi                   138                   138

89Sn-3Bi-8Zn                                      189-199

Where there is a single temperature in the melting range column, the solder is eutectic.

Based on:

V. Solberg, “No-Lead Solder for CSP: The Impact of Higher Temperature SMT Assembly Processing,” Proc. NEPCON West 2000 Conf. (Feb. 28 - Mar. 2, 2000) Anaheim, CA (Source: Indium Corp.) # N.-C. Lee, “Lead-Free Chip-Scale Soldering of Packages,” Chip Scale Review, March-April 2000.

Source:

http://www.msed.nist.gov/solder/NIST_LeadfreeSolder_v4.pdf

Solidus and Liquidus Temperatures of Some Leadfree Alloys on Copper

Alloy  %                             Solidus (°C)        Liquidus (°C)

98Sn-1Ag-1Sb                      222                   232 

89Sn-4Ag-7Sb                      230                   230

91.2Sn-2Ag-0.8Cu-6Zn          217                   217

89.2Sn-2Ag-0.8Cu-8Zn          215                   215

89.2Sn-10Bi-0.8Cu               185                    217

85Sn-10Bi-5Sb                     193                   232

52Sn-45Bi-3Sb                     145                   178

42Sn-58Bi                            138                   138

Based on:

M.E. Loomans, S. Vaynman, G.Ghosh and M.E. Fine, “Investigation of Multi-component Lead-free Solders,” J. Elect. Matls. 23(8), 741 (1994)

Source:

http://www.msed.nist.gov/solder/NIST_LeadfreeSolder_v4.pdf

Eutectic Composition of Solders

Most solders and especially tin-lead alloys have a melting (or pasty) range between which the metal has moved from a proper solid (solidus) to a completely liquid (liquidus) state.  Wide melting ranges are ideal for plumbers, they are not for electronics, or stained glass.  It is much easier to run a nice bead with a narrow range of melting (pasty) temperatures.

Some alloys of solder have what is known as an eutectic characteristic.  This is where the liquidus and solidus states occur at the same temperature.  A composition of 61.9% tin and 38.1% lead is both eutectic and the melting occurs at a minimum temperature.

For comparison with lead free solder characteristics the following % compositions of Tin (Sn), Lead (Pb) and Silver (Ag) solders are given.

Element % of solders  Melting point        Comment

Sn 62, Pb 36, Ag 2       179                    Eutectic; traces of antimony

Sn 63, Pb 37               183                    Eutectic; traces of antimony

Sn 60, Pb 40               183-191             Traces of antimony

Sn 96.3, Ag 3.7           221                    High melting point. Eutectic

Sn 10, Pb 90               275-302

Sn 3, Pb 97                275-320

Sn 5, Pb 93.5, Ag 1.5   296-301

Source:

http://en.wikipedia.org/wiki/Solder#Lead-free_solder

Conclusions

Most of the alternative solders contain tin as it assists in the formation of bonds with a wide variety of metals.  These solders are also mechanically weaker than tin-lead solders.  Lastly, they are much more expensive than tin-lead solders.  Even within the tin-lead solders there is a variation in price, as tin is much more expensive than lead. If high temperatures were not a problem, you could use a high lead content solder.  However, that also raises the liquidus temperature and increases the pasty range.

The choice in lead free solders is between the high liquidus temperatures of the less expensive compositions and the high price of the eutectic, or nearly so, ones.  The lowest eutectic composition is the Tin-Bismuth solder, but it is also among the most expensive to buy.  You should also note that the inclusion of copper in the composition prolongs the life of the solder bit, as low lead content of the solder leads to the incorporation of small amounts of copper from the tip into the solder joint.

Simple Investment Mould Materials

There are a lot of differing recipe options for making plaster moulds. A simple general purpose investment mould making material and method follows:

Equal parts of powdered silica (sometimes called silica flour or flint), plaster of Paris and water by weight.  For example:

1 kilo silica
1 kilo Plaster Paris
1 kilo water

(Do not measure by volume)

Mix silica and plaster of Paris dry in separate bucket by hand.  If you can use a closed container that is best.  Otherwise use breathing protection and do the mixing outside.  Silica is very bad for your health.

Measure the water into a separate bucket with enough volume for three times the amount of water. Slowly sprinkle the entire contents of the dry mix into the bucket of water.  Do not dump it in!

Let the mixture sit for 2 minutes (slaking).  Then mix by hand slowly to prevent bubbles. Using your hands allows you to feel any lumps that are present and break them down gently. Depending on temperature and amount of water, you have 15-20 minutes before the mix begins to become solid.

When mixed thoroughly, pour carefully and slowly into a corner of the mould box or container to reduce the occurrence of bubbles within the investment material or against the master.

When the pour is finished, tap the mould container to encourage any bubbles to the surface.

You can take the investment and master from the container once it is cold to the touch. Remove the master from the investment material carefully to avoid damaging the surface of the investment.

For pate de verre, you can use the mould almost immediately.  For casting, it is important to have a dry mould.

Let the whole air dry. Depending on the temp, humidity and density this can last from several days to several weeks. A way to tell how dry the investment is, is by weighing the mould when it has just hardened. When it has lost on third of its weight (the water component), it is ready for kiln drying. This removes the chemically bound water from the investment material. 

This is only an outline of what to do.  Investment moulds are extremely complicated in their chemistry, physics, and use.

Mica

What it is

Mica is widely distributed throughout the world and occurs in igneous, metamorphic and sedimentary rocks. Mica is similar to granite in its crystalline composition.  The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms.

Mica can be composed of a variety of minerals giving various colours and transparency. Purple, rosy, silver and grey colours come from the mineral called lepidolite.  

Dark green, brown and black come from biotite.  

Yellowish-brown, green and white come from phlogopite.  

Colourless and transparent micas are called muscovite.  

All these have a pearly vitreous lustre.

The melting point of mica depends on its exact composition, but ranges from 700⁰C to 1000⁰C.

Glass has a specific gravity of about 2.5, and mica ranges from 2.8-3.1, so it is slightly heavier than glass.

Tips on uses of mica powder and flakes

The naturally occurring colours are largely impervious to kiln forming temperatures.  Other added colours have various resistances to the heat of fusing. This is determined by the temperatures used to apply the colour to the mica.  Cosmetic mica is coloured at low temperatures and will not survive kiln forming with their colour in tact.

Mica does not combine with glass, but is encased by glass as it sinks into the glass surface.  You can use various fluxes to soften the surface of the glass.  Borax is one of those.  The cleaving of the mica results in only the layer in contact with the glass sticking.  The upper layers brush off.  This applies to both powder and flakes. One solution is to fire with mica on top in the initial firing and then cap for the final one.

When encasing mica exercise caution. Micas flakes must be applied thinly, as air is easily trapped between layers which leads to large bubbles from between layers of glass.  This is the result of the shearing of layers of the flakes allowing air between layers.  Although powdered mica is less likely to create large bubbles, air bubbles are often created for the same reason.  This is the reason it is most often recommended to fire the mica on top. 

Of course, one use of the mica to make complicated designs is to cover the whole area and fuse.  Then sandblast a design removing the mica from areas of the glass. You can then fire polish, or cap and re-fire to seal the mica.

Mica safety

MSDS for mica only mentions the inhalation of the dust as a risk. Mica is resistant to acid attack and is largely inert.  Inhalation of the dust is a (low level) risk.  Any significant health and safety problems relate to the coloured coatings.

Solder for Zinc

A number of people seem to have difficulty soldering zinc around their projects.  This is because zinc transmits the heat quickly – more quickly than the tin/lead solder – requiring more heat to be put into the process.  There is a solder that can make this process easier as it is designed for soldering zinc.

“Galvanite is a lead-free galvanizing solder formulation designed specifically for high quality repairs to galvanized steel surfaces. Simple, effective and easy to use, in both manufacturing and field applications. It metallurgically bonds to the steel, for a seamless protective barrier.”

https://en.wikipedia.org/wiki/Solder#Lead-free_solder

It composition is 50% tin, 49% zinc and 1% copper.  It becomes solid at 200C and liquid at 300C.  This makes it a high temperature solder for stained glass purposes, but will give a firm attachment between the zinc and the solder or lead came it surrounds.  The high temperature aspect means you need to keep the iron on the zinc rather than the more easily soldered metals or the glass.

Lead Free Solder

Lead free solder is being required for the electronics industry, but not yet for the stained glass industry.  However, some people are beginning to use lead-free solders for other reasons.  In general, it is reported that it is harder to get smooth beads.  Some reasons may relate to the physical properties of the material being used.

Lead free solder solidifies at a higher temperature than the common tin/lead solder compositions although the common lead free solders melt at slightly lower temperatures.  For comparison purposes characteristics of some common lead free solders are given with the common tin/lead solders.

Sn = Tin,   Ag = Silver,   Cu = Copper   Pb = Lead

Solidus = solidification temperature.   Liquidus = Melting temperature

96%Sn, 4%Ag which has a Solidus of 221C and Liquidus of 229C

95%Sn, 5%Ag which has a Solidus of 221C and Liquidus of 254C

Slightly less commons is

96.5%Sn, 3.5%Ag which has a Solidus of 221C and Liquidus of 221C, but has poor wetting properties except on stainless steel.

Other solders are available up to 7% silver, but these are increasingly expensive and have much higher liquidus points.

A truly eutectic lead free solder can be produced with 95.6%Sn, 3.5%Ag, and 0.9Cu, which has a Solidus and Liquidus temperature of 217C

For comparison:

63%Sn, 37%Pb has a has a Solidus of 183C and Liquidus of 183C

60%Sn, 40%Pb has a has a Solidus of 183C and Liquidus of 188C

50%Sn, 50%Pb has a has a Solidus of 183C and Liquidus of 212C

40%Sn, 60%Pb has a has a Solidus of 183C and Liquidus of 238C

The solidus temperature of lead free solders is almost 40C above the tin/lead solders.  This may be the reason people find the need to turn up the heat of their soldering iron when using lead free solders.  The difference in the Liquidus and Solidus points for 4%Ag is very similar to that for 60%Sn/40%Pb.  So with enough heat should behave similarly.

Physical Characteristics of Solder

Solder is an alloy of various materials.  The most common ones for leading and copper foil work are tin, lead, copper and silver.  The most important is tin.  There are, of course, some solders that do not have tin in their composition.

The most common alloy for us is tin and lead.  Various proportions produce different melting (liquidus) and solidification (solidus) points.  This graph shows the effect of changing the amount of tin in a tin/lead solder.

This shows that 61.9% tin and 38.1% lead produces an eutectic solder (although others report a 63/37 alloy as eutectic).  That is, a solder which has both its liquidus and solidus temperatures the same.  This kind of solder solidifies very quickly after its melting.  If we put a lot more heat into this kind of solder, it takes time to become solid.  During that cooling, the solder bead can become disturbed and become either crystalline or marked.  The objective should be to move quickly enough to melt the solder, but not to dwell, as that adds heat.

For the other common combinations [insert ref to previous blog entry] there is a temperature range where the solder is pasty.  It is neither fully liquid (needed to get a good bead) nor yet solid.  It is in this range that various problems can arise.

Failing to get the solder to the liquidus state will result in what is called a cold joint.  The solder is crystalline at the visible level.  It has visible cracks and will not adhere to the copper foil or lead properly.  If disturbed while the temperature is in the pasty range while cooling from the liquidus state, you will also get a crystalline structure to the solder, resulting in an insecure joint.

The graph also shows the melting points of lead (327.5C) and tin (232C).  The wonder of an alloy is that by combining these two metals, the solidus points are greatly changed. This graph shows is that tin is not fully solid until 13C, while lead is solid immediately below its liquidus point, but by combining them a solidus temperature of 183C is achieved.

This graph, with different temperatures, is applicable to lead free (tin and silver mainly) solders too.  The solidus point is about 40C above that for tin lead solders.

Information on specific solders is given here and here