Wednesday, 27 May 2020

Oxidisation of Foil

Often, life intervenes between foiling and soldering.  This frequently results in the foil not accepting the solder very well, because of the mild tarnish that has occurred in the meantime.

It is a good idea to clean the foil of any possible corrosion before soldering when there has been an interval between the two processes. It is enough to clean foil with a mild abrasive such as a foam-backed scrubber from the dish washing, or fine steel wool.  I prefer the scrubber as it does not introduce another metal.  

Some people prefer a vinegar and salt solution to apply to the tarnished foil.  I am concerned about the introduction of an acid into the process causing further problems later.  I don't recommend this method of cleaning.

I then coat the exposed foil with a film of paste flux to protect from further tarnish. This acts better than any loose covering of cloth or plastic to protect from oxidation.  The purpose of flux is to both provide a "wetting" agent for the foil to accept the solder,  and to prevent oxidisation. Liquid flux cannot provide protection, once dry,  from the copper tarnishing.  I prefer the use of paste flux to reduce boiling of flux and to keep the copper free from corrosion.  The paste flux will not indefinitely prevent oxidisation, but will do so for a week or two.

Wednesday, 20 May 2020

Pin holes in melts

Pin holes in screen and pot melts are the result of very small bubbles rising to the surface.  These bubbles are sometimes within the glass melted, but more often come from small amounts of air trapped within the flowing glass.  These are perceived to be unsightly, or make it impractical to make a functional piece from the melt.

There are ways to minimise bubble formation or to deal with the formed bubbles.

Bubble Formation
In pot and screen melts, the glass spirals as it touches down onto the shelf. This spiralling action can trap small amounts of air as each successive spiral forms beside the previous one. Efforts at prevention of tiny bubbles in the final piece need to concentrate on this fact.

A preliminary element in bubble prevention is to have a long bubble squeeze to allow the glass to settle in the pot or on the screen so that the rest of the process can proceed with a minimum amount of air trapped within the flowing glass.

Two-Stage Drop
In some cases. it is possible to have the glass flow from the pot onto an angled shelf where the spiralling glass has to flow from the initial touch down to the edge and then flow onto the shelf.  This allows any tiny bubbles initially trapped to escape before the final drop onto the shelf.  This provides two mixing processes and means that a lot of clear glass needs to be included to avoid a complete mix of the colours.  It requires careful selection of the original colours to avoid a brown or black result.  It also requires a big kiln with sufficient height for a two stage drop.

This two-stage drop is of course, not suitable for a screen melt where you wish the glass strands to remain.  Nor is it suitable when you wish to have many “pools” of colour mix in the final piece.

Where the two-stage drop is not practical or suitable other methods can be used.  These relate to scheduling, cold working the surface and re-firing the piece.

Scheduling relates to using a soak at full fuse temperature before proceeding to the anneal.  The melt will occur at 850°C to 950°C.  You can cool as fast as possible to a full fuse temperature of about 810°C and soak there for an hour or more.  This allows the small bubbles to surface, break and heal.  Schedule the rapid cool to the annealing soak, once the high temperature soak is complete.  This will eliminate lots of the bubbles, but not all.

A sample friring schedule from bubble squeeze upwards and then down to a high temperature bubble reduction soak

Cold Work
Cold working the melt is about abrading the surface to open the bubbles that are just emerging to form a small dome at the surface.  Sand blasting is a common form, as usually kiln wash or fibre needs to be removed from the bottom of the melt, and some devitrification from the surface.  It would be possible to continue to grind the surface of the glass to eliminate the small depression in the glass caused by the now opened bubble, but this is likely to expose more bubbles that were at a slightly deeper level. What next?

As you will need to do a fire polish firing after blasting or grinding the surface, you can use a full fuse temperature to allow the surface to become plastic enough to fill the bubble holes.  Remember to schedule the firing as though the piece were at least 12mm thick.  You may find that more bubbles are exposed in addition to the ones healed at the conclusion of this second firing.

An alternative is to fire upside down.  You will have noted that there are no bubbles on the bottom of the melt.  This is because the bubbles have risen through the heated glass.  This physical fact can be used in the second firing.  Fire with the melt surface to the shelf.  It is best to have a clean and newly kiln washed shelf, or fibre paper (not Thinfire or Papyros) under the glass. Fire the glass to a full fuse or high temperature tack fuse with a significant length of soak to allow the bubbles near the original surface to move toward the interior of the glass.  After firing, the glass will need thorough cleaning before being fire polished. This should leave you with a pin hole free piece.

Achieving a pin hole free pot or screen melt requires several stages of coldworking and firing.  This makes melts inexpensive in materials (it is scrap of course) but expensive in time and firings.

Wednesday, 13 May 2020

Strong Frames for Stained Glass Panels

Zinc is a popular material for framing copper foiled or leaded glass panels.  It is stronger than lead – up to eight times.  It gives a feeling solidity to the edges of the panel. 

However, it does have some disadvantages.  It is difficult to patina evenly and obtain the same colour as patinaed solder.  It resistance to progressive corrosion is weaker than lead. It requires special tools to fit around curves, making it best for rectangular panels.  It does need a saw to cut evenly, but so do a lot of the stronger metals.  A look at other options is worthwhile.

The strongest option is stainless steel.  This is difficult to cut and has special welding requirements, so is only useful in large and high corrosion installations.

Mild steel is widely available and cheap.  In certain circumstances – mainly small, thin profiles – it can be soldered.  The most secure joining is done with welding.  This requires equipment that stained-glass workers do not usually have.  However, there are a large number of metal workers that can to the work for you.

Brass is more expensive than mild steel.  It is an alloy of copper and tin and so can be soldered with the tools we normally use.  It is about half the strength of stainless steel, but three times the strength of zinc.  The tin content leads to a better patina result than zinc.

Copper is up to twice the strength of zinc, but the price fluctuates more than zinc.  It can be soldered. It requires different patina solutions than used for solder.

Aluminium is the same strength as zinc, but requires different joining methods as aluminium welding is a specialist activity.  Still, it will work on rectangular items with screws at overlapping joints.

More information on the relative strengths of various metals is given in a post on metal strengths.

Strengthening lead came
Lead is weaker than lead but can be bent to conform to curves and indentations for irregular perimeters.  If copper wire is incorporated and attached to the foiled glass, the soldering of the lead came to the joints at the intersections of the solder lines and the coper/came combination will provide greater strength than the zinc alone. 

When wanting to strengthen the perimeter of rectangular or shaped perimeter leaded panels, you can use 10mm “H” lead came soldered as usual to the whole piece as an alternative to soldering the wire to the panel.  Run the copper wire in the open edge of the “H”.  Pull the wire tight at the bottom and sweat solder at each corner.  Run the wire to the top on each side, where you can make a loop for attaching hanging wires and sweat solder the wires there too.  Then close the two leaves of the lead with a fid until they come together forming a single straight line.  If you want, a “U” or “C” edging came can be soldred to the outer edge of the "H" came to cover the line created by folding the leaves.

This post gives more detail about the process of incorporating copper into the perimeter of a leaded panel.

Wednesday, 6 May 2020

Pot Melt Saucers as Dams for Melts


Many ceramic plant pot saucers can be used as circular moulds.  Most are unglazed and will accept kiln wash easily.  Some are unglazed, but polished to such an extent they are no longer porous.  These and glazed flower pot saucers need some preparation before applying kiln wash.

Plant pot with saucer

Polished and glazed saucers require roughing to provide a key for the kiln wash solution to settle into.  This can be done with normal wood working sand papers.  You may want to wear a dust mask during this process, but not a lot of dust is created.  You could also use wet and dry sandpaper or diamond handpads with some water to reduce the dust further.

If the sanding of the surface does not allow the kiln wash to adhere to the saucer, you can heat it.  Soak it at about 125C for 15 minutes before removing it from the kiln to get the heat distributed throughout the ceramic body.  One advantage to the ceramic is that it holds the heat, because of its mass, for longer than steel.  Apply kiln wash with a brush or spray it onto the warm saucer.  As it dries, apply another layer of kiln wash.  Two or three applications should be enough to completely cover the surface.  If not, then you probably will need to heat up again before repeating the process.

Alternatives to plant pot saucers

There are alternatives to the saucer approach to getting thick circles from a pot melt.


Fibre paper
You can cut a circle from fibre paper and melt into that.  The advantage of fibre paper is that it requires little preparation other than cutting and fixing.  You may have only 3mm fibre paper and want a 9mm thick disc.  Simply fix the required number of layers together with the circle cut from each square.  The fixing can be as simple as sewing pins, copper wire, or high temperature wire.  Then place some kiln furniture on top of the surrounding fibre paper to keep it in place on the shelf during the melt.  This furniture can often be the supports for the melt.

Fibre board
If you find cutting multiple circles of the same size a nuisance, you can use fibre board.  Simply cut the circle from the board with a craft knife.  You will probably want to line the circle with fibre paper, as the cut edge of fibre board can be rough.  Alternatively, you can lightly sand the edge.  Wear a dust mask and do this outside, if possible, to keep the irritating fibres away from the studio. If you want a thicker melt than one layer of board can give, just add another in the same way as for fibre paper.

In both these cases, you may wish to put down a layer of 1mm fibre paper to ensure the glass does not stick to the shelf and does not require sandblasting.  

The advantage of the fibre paper or board alternative to flower pot saucers is that you do not need to kiln wash anything unless you want to. If you do not harden the fibre paper or board, it will not stick to the glass.

Vermiculite board
Another alternative is vermiculite board.  The advantage of this is that it comes in 25 and 50 mm thicknesses, so you can make the melt as thick as you like without having to add layers.  You can cut the vermiculite board with wood working tools.  Knives will not be strong enough to cut through the vermiculite board. You will need to kiln wash or line the vermiculite with fibre paper, as the board will stick to the glass without a separator.

Damless circles
Of course, if you want a circle without concern over the thickness, you can do the melt without any dams. You need to ensure that the shelf is level.  Any supports for the pot will need to be both kiln washed and far away enough that the moving glass does not touch the supports and distort the circle.  In general, one kilogramme of glass will give a 300mm circle, so your supports need to be further apart than the calculated diameter of the circle.  An undammed circle will vary from 6mm at the edge to as much as 12mm at the centre, depending on temperatures and lengths of soaks.

Wednesday, 29 April 2020

First Firing of your New Kiln

First Firing of your New Kiln

I have just been reviewing information on kiln elements. I have discovered the reason you need to do your first firing with the kiln empty of everything. No kiln wash, no kiln furniture, nothing. Vacuum the kiln to take out any dusts from travel.

The element forms a protective layer of aluminum oxide during the first firing. If there are elements of kiln wash, dusts, or glass, this will inhibit the ability of the oxide coating to be uniform. The uniform coating of the elements is important to the long life of your elements. There are other things of course, but this is the initial, essential element of preparing you kiln for use.

After this first firing you can add the other elements of kiln wash, furniture, and even glass.

In summary, fire your kiln clean and bare. No kiln wash, no furniture.

Sam Smith adds: [This] applies to kilns made with Kanthal A1 elements. Those are the good ones which last pretty much forever. Cheaper quality kilns can have nichrome elements which do not develop the coating. The firing the kiln empty allows the oxide coating to form. If you do a firing where combustion takes place such as firing fibre paper or shelf paper you should realize those combustion products are attacking your element coatings and it may be worth while venting the kiln and or firing the kiln up empty after the firing in order to protect or allow the development of a new layer of coating covering the kanthal. Kiln wash us is cheaper and safer for the long term life of your kiln elements. Smart people only purchase kilns with Kanthal elements.

Wednesday, 22 April 2020

Bubble Squeeze for Multiple Layers

Difficulties often occur with bubble formation within pieces composed of several layers. There are a couple of factors in addition to the number of layers that have an influence - temperature and rate of advance to the bubble squeeze temperature.

The top temperature for the bubble squeeze does not need to change with multiple layers. It is the advance to the bubble squeeze that needs to change in relation to the number of layers.

Rate of Advance
It would  be suitable to reduce the rate of advance to about three-quarters of the two-layer schedule to account for three layers.  And a reduction to one half of the two-layer schedule for a four-layer piece would be appropriate. The reasons for these slower rates of advance follow.

A normal rate of advance for two even layers would be about 200°C per hour to the bubble squeeze temperature.  Sometimes a very slow rate of advance is used from 50°C below the top of the bubble squeeze.  This strategy can continue to be used for thicker pieces made up of many layers with some modifications.

Multiple Layers
But for a three-layer piece, slowing the rate of advance to about 150°C is important to assist in a good bubble squeeze.  This helps get all the glass at the same temperature by the time the bubble squeeze is approached. Glass is a good insulator, and also a poor conductor of heat. This slower advance allows the bottom layer to be at the same temperature as the top piece.

For a four-layer piece, a rate of about 100°C would be suitable.  When the lower point of the bubble squeeze is reached (about 50C below the upper soak), the slow rate of advance can be used to go to the upper end of the squeeze, using the normal soak length.  

This illustrates that the more layers of glass in the stack, the slower the rate of rise must be in the bubble squeeze range.

Five Layers and Beyond
For pieces made up of more than four layers, a different strategy is needed to ensure the heat reaches the bottom layer of glass.  Graham Stone* calls this the “catch-up” schedule. It is essentially an overnight schedule with temperature equalisation soaks of 20 minutes at 125°C intervals all the way to the bubble squeeze. At each stage the rate is increased by 10°C.

This means that with a first segment rise of 20°C per hour, the second from 125°C to 250°C is at 30°C with a 20 minute soak, then 40°C to 375°C soak for 20 minutes, 50°C to 500°C and soak for 20 minutes, and finally 60°C to 625 for a final 20 minutes with 70°C to your normal bubble squeeze temperature.  This will take about 17 hours before you go on to the forming temperature.

This long heat up schedule illustrates the problem of getting the heat to the bottom layers of the stack, and the need to squeeze the air from between the layers.

Thicker pieces apply more weight to press out bubbles from lower layers, but only if the lower layers are equally as hot as the top.  This requires long schedules.

An alternative approach to this bubble squeeze problem is to fuse two layer pieces of the appropriate number to achieve the thickness required.  If these are fired with good bubble squeezes there will be a minimum of bubbles.  Combining these 6mm blanks will give fewer bubbles with a proper bubble squeeze.

Another approach is to start with 6mm glass as it comes from the maker.  This is not always possible, because it is not common for 6mm fusing glass to be made in anything but clear.  It may be possible to incorporate the clear within the stack, if it is not appropriate on the bottom.  These thicker sheets have fewer bubbles proportionally than 2mm or 3mm sheets.  So there are fewer bubbles in the final piece.

Of course, placing shards of glass at the corners, or sprinkling a very thin even layer of powder between multiple sheets will also help reduce bubbles between layers, but it is the slow rate of advance to the bubble squeeze that is the important element.

*Firing Schedules for Glass; the Kiln Companion, by Graham Stone, 2000. ISBN 0-646-39733-8

Wednesday, 15 April 2020

Texture Mould Firings

Texture moulds are essentially permanent kiln carving moulds.  These are moulds that use different levels within the mould to develop the imagery by giving different thicknesses to the glass. Temporary or single use moulds can be made from fibre paper, although not with the same subtlety as the ceramic ones.

Single layers
Many people wish to use a single layer in these texture moulds. For a single layer, a tack fuse is a high as you can take the temperature. This will not give you the definition that you could get with higher temperatures unless you use very long soak times. 

Good definition
To use higher temperatures, you need at least two layers (6mm) to avoid distortion, dog boning, possible bubbles and needling.  With two layers you can go to full fuse temperatures to get the best conformation to the mould.

Low temperature firings
You can get better definition at lower temperatures by going slowly to your target temperature. This slow rise in temperature – ca. 100C - or less - per hour – all the way to the lower end of the tack fuse range – ca. 730C to 750C -  needs to be combined with a long soak, possibly two or more hours.  This long soak allows the glass to sink into the depressions of the mould without shrinking, dog boning or needling.  This shows that the speed you use has a major effect on the target temperature.

Another element of difficulty in the use of these moulds is the separator used. Kiln wash is adequate, especially if you are using the lower temperatures.  Boron nitride is a popular choice for those going to higher temperatures.  Using iridescent glass with the coated side down to the mould provides an additional separator, allowing higher temperatures to be used.  It can enhance the appearance of the piece too. 

The way you schedule for texture moulds is an interaction between the thickness of the glass, the rate of advance, the target temperature and the kind of separators used. With these four factors interacting, the choices are not simple.

Wednesday, 8 April 2020

Long Annealing Times

I’ve noticed a lot of people are using long annealing times for full or contour fused glass of 6mm thickness.  Whether this comes from the advice for tack fused pieces to be annealed as though there were twice the total thickness of the piece, or not, is uncertain. 

Temperature Equalisation

This term employs the concept of what happens at the annealing point chosen for your glass.  The soak at the annealing point - or even at some degrees below - is the process of ensuring the glass is all at the same temperature before proceeding to the annealing cool.

A “flattish” fused piece of 6mm needs only a half hour when the temperature equalisation soak is at the annealing temperature.  When using a temperature equalisation soak about 30°C-35°C below the annealing temperature – as Bullseye, and now Wissmach, does – you may need an hour.

Tack fusing is much more difficult to anneal properly than a full or contour fuse.  The general rule of thumb has become that you must schedule the firing as though it is twice the actual maximum height. 

E.g., if you have a two-layer piece with other pieces distributed around this flat base, you have a 9mm thick piece in total height. Scheduling for this piece as though it is 18mm thick requires longer soaks and slower cools.  In this case, you should schedule for a three-hour soak at temperature equalisation, whether using the annealing point or a lower temperature. 

Other kilnformers have found that firing tack fused pieces as though they are one and a half times the actual maximum thickness provides a perfectly adequate result.  It will be up to each person to decide which approach they take.  Once the current lock down is over, I am going to do some work on the actual requirements.

Annealing Cool

People seem to cool a tack fused piece at a rate suitable for thinner pieces. It appears that the general practice is to use rates suitable for a for 12mm thick piece regardless of the calculated thickness. 

But the annealing cool is still too rapid for a tack fuse.  If you need an anneal soak for 19mm, you need to cool for that thickness too. An annealing cool for a 19mm piece is one half of the rate of that for a 12mm piece.  It is during this too rapid cool that stress can be induced, especially on a tack fused piece.

The temperature equalisation soak and anneal cool can take as much as twice - or more – as long as a flat piece of the same total height.  This needs to be allowed for in the scheduling of the firing.

The length of anneal soak and the rate of anneal cool both need to be related to the appropriate thickness.  There is the Bullseye chart for annealing thick slabs the rates of which, can be applied to any fusing glass.  You only need adjustment to the temperatures for your glass, if not Bullseye.

Wednesday, 1 April 2020

Extending the Annealing Soak


There is a common assertion that you need to extend the annealing - or temperature equalisation soak - on each firing after the first.

The rationale for this is never fully explained.  Possibly it comes from the fact that you need to reduce the rate of advance on already fused pieces over the unfused lay-up. It is also possible the rationale is that since you need to slow the rate of advance, so you need to extend the anneal soak.

However, if this is the rationale, it is rarely followed through on the anneal cool in the detailed schedules in these instances.  Generally, the cool on extended soaks is the same as on the first anneal, but extending the anneal should apply to the cool too, according to this kind of rationale.


At normal kilnforming temperatures, the anneal for the determined thickness (allowing a doubling of thickness for tack fused pieces) is suitable even for multiple firings.

Once you go up into the temperatures for melts, there is reason for more caution. There is the risk that the high temperatures – especially for hot coloured opals – may induce a little incompatibility.  A longer soak for these may be considered desirable.  Even so, this does not need to be extended at each subsequent firing. 

You are annealing at each firing for the thickness – actual or calculated – of the piece, not for the number of firings.

Extending the length of the anneal on each subsequent firing is not necessary unless additional thickness or complexity has been added.

Monday, 30 March 2020

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:

Soldering Lead Came

Soldering lead came is different from soldering electronics or copper foil. For electronic soldering less heat is needed, cleanliness is all important, suitable flux is required, and the iron is held differently, among other things.

Soldering lead came The lead needs to be clean and bright to start with. If it's fairly new lead it should be solder-able without more than a scrubbing of the joints with a brass wire brush. However, if the lead is dull and oxidized, you should scrape the lead in the area to be soldered with a nail, the blade of a lead knife or other sharp edged tool until the bright metal is revealed.

an example of paste flux
Example of a tallow stick.  It has the appearance of a candle, but without the wick.

Example of the application of tallow to a joint

Then the flux can be applied.  Paste flux or tallow works best as neither flows in its cold state.  This means that you can flux the whole panel at one time without the liquid flowing away or drying.  Once the whole panel is fluxed, you do not need to stop during the soldering process.

Example of a gas powered soldering iron. The flat face of the soldering bolt is held in full contact with the joint.

An electric soldering iron is held over-handed (as you would a bread knife) in order to get the handle low enough to have the tip flat on the lead. This will be a 15 to 20 degree elevation from the horizontal. Allow the weight of the soldering iron to do the work for you. 

Let it rest on the joint after you apply the solder between the lead and the iron. In order to heat both pieces of lead you may have to rock the tip slightly to contact all leads being soldered. Take the solder away from the iron so it doesn't become attached to the joint. As soon as the solder spreads, lift the iron straight up. This process will take only a few seconds, much less than 5.

Example of smooth flat solder joints.

Avoid "painting" or dragging the iron across the joint. The object is to have a shiny, smooth, slightly rounded solder joint. Moving the iron and solder around does two things.  It makes for a weak joint as the solder does not have the chance to become stable and so forms a "pasty" joint.  Moving the iron around during the soldering of the joint often provides sharp points where the iron was moved quickly off the join. There should be no points sticking up from the solder joint. If a solder joint is not satisfactory you can re-flux and re-heat. Don't apply too much solder. It's easier to add more solder than to remove excess.

Sunday, 29 March 2020

Soldering Irons and Rheostats

People often want to have variable temperatures for decorative soldering.

It is recommended to use a rheostat in circumstances where the soldering iron does not have an internal temperature control.

A rheostat is NOT a temperature controller.

Action of a Rheostat
A rheostat actually reduces the power supplied to the iron, thereby making it take longer to heat or re-heat after a period of soldering. Without a rheostat, if an iron is left idle, it will eventually reach its maximum temperature. This is usually too hot for soldering lead, but OK for joining other metals. With a rheostat, if an iron is left idle with the rheostat set to (say) '6', it will still reach its maximum temperature but very much slower than the one without a rheostat.

Action of a Temperature Controlled Iron
Temperature controlled soldering irons attempt to maintain a set temperature. This is controlled by the combination of the microchip in the iron and the tip. So to adjust your temperatures all you need is a few different tips. For example, a number 7 tip lets your iron heat to 700F degrees. For decorative soldering your need tips of lower temperatures, usually a number 6 or 600F degree is enough of a reduction for most decorative stuff. A number 8 tip (800F) will let you work at a higher temperature if you work quickly.

Differences in Soldering Speed
Using an iron without a rheostat, provided you work relatively quickly, you will probably be able to solder all the joints in a small or medium panel without stopping to let the iron 'catch up'. In this case the temperature is controlled by the heating power of the iron balanced by the cooling effect of making the soldered joints.Using an iron with a rheostat, you will need to slow down a little if you are to do that same panel without stopping to let the iron re-heat. In this case the temperature of the iron is controlled by the (reduced) heating power of the iron balanced by the same cooling effect of making the soldered joints.This difference is caused by the fact that a temperature-controlled iron, if it is left idle, it will quickly reach its maximum operating temperature - just as quickly as an un-controlled iron of the same power. When you start soldering, the cooling effect will trigger the temperature controller to provide full power until the operating temperature is reached again.

Advantages of a Temperature Controlled Iron
You can buy an iron (not temperature controlled) and a rheostat but buying tips for the temperature controlled iron is cheaper. The big advantage of the temperature-controlled iron is that you know it will never get too hot for the work you are doing, and that it truly provides that 100 watts (or whatever) power to keep it hot even when you are soldering at top speed.

Choosing a Soldering Iron

The iron used to solder must be of a high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. The tip can't be so small it can't maintain the heat nor so big it covers more area than wanted.

For example a 75 or 80 watt iron is sufficient to begin soldering with, but it will continue to get hotter, as it has no temperature control. An iron of this type should be used with a rheostat in order to prevent overheating while it is idling.

Most temperature controlled irons seem to be produced in 100 watts or higher. These internally temperature controlled irons maintain a constant temperature. They are normally supplied with a 700F° bit (number 7) and is sufficient to melt the solder without long recovery times. You can obtain bits of different temperature ratings, commonly 800F° and 600F°. You can also several sizes of tips for different detail of work.

  For volume work you can obtain temperature controlled irons of 200 watts and more.

It is also possible to obtain a Japanese made soldering iron with the rheostat built into the handle.

Soldering irons

Historically soldering tips were copper, placed in braziers. One tip at a time was used; when the heat had transferred from the tip to the solder (and depleted the heat reserve) it was placed back in the brazier of charcoal and the next tip was used.

Much later gas irons were in common use. These used a gas jet to heat the soldering bolt/tip. They are very fast, but require significant amounts of experience to properly regulate the temperature.

Currently, electric soldering irons are used; they consist of coil or ceramic heating elements, which retain heat differently, and warm up the mass differently, with internal or external rheostats, and different power ratings - which change how long a bead can be run.

The soldering iron used must be of a high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. The tip can't be so small it can't maintain the heat and not so big it covers much more area than wanted.

For soldering leaded panels a 100w iron with a 3/8" temperature controlled tip that maintains a constant 370°C (700° F) is suitable.

For copper foil a higher temperature controlled tip is used. This normally runs at 425°C (800°F). Sometimes a tip of ¼” is used where more delicate beads are being run. But there is little difference in the resulting bead - only that the smaller bit takes slightly longer to heat up.

If a lot of soldering is required that has sustained heat requirements, you might consider a 200W iron. These can deliver heat more quickly and evenly than those with lesser wattage.

Trimming the Came on Site

There are a variety of reasons for the panel not fitting the opening easily. These can range from poor measurements through parallel, or trapezoidal openings to irregular perimeters of the openings.

In the cases of irregular openings, you can trim the edge cames if you have used 12mm (1/2”) or more wide came. The quickest way of trimming cames to fit the opening is to use a rasp or “surform” tool. The open nature of the teeth, allows the lead to fall away. It is much quicker than using a lead knife, and it puts less pressure on the panel.

Cementing Leaded Panels, part 3

Polishing Lead Cames

Use a soft brush to polish lead came. Don't pick out the cement until the polishing is done, as it provides the colour for darkening and polishing the lead and solder joints. The action with the polishing brush should be gentle and rapid, much like polishing shoes. If the shine does not come, you can use a very little stove blackening (carbon black mixed with a little oil) If you use a lot, you will have a big clean up job. A little stove blackening spreads a very long way.

Before turning the panel a final time, put down paper or cloth, to avoid scratching the solder joints while polishing the other side. The result should be shiny a black came and solder joints that does not come off the way a final buffing with stove blackening does.

Finally, pick out any remaining cement.

Rest horizontally with weather side down for traditional installations. If the panel is going into a double or secondary glazed unit, you may want to reverse this. The reason for having the smallest exposed cement line on the outside is to allow the water to run off the window with the minimum of area to collect. In a sealed unit or for secondary glazing, you may want to have the smallest amount of cement showing inward for appearances, as there is no weathering reason for the traditional method.

Rest for a day. Pick out the cement again. If the cement was stiff enough, there should be no need to do any more picking at the cement after this.

Cementing Leaded Panels, part 2

Part 2: Setting Up the Cement

After the pushing the cement under the cames on both sides, flip the panel over and begin a firm rubbing to push addidional cement into the gaps between the lead and glass on this side. Sprinkle the used dust from the bench top over the panel and rub in all directions. This begins to set up the cement by helping to provide a stiff skin over the more fluid cement. Brush until the whiting is largely off the panel. Turn the panel and do the same for the other side. Several applications of whiting/sawdust are required to give a sufficiently thick skin to reduce the amount of spreading, leaking or weeping cement.

Once both sides have been done a couple of times, begin to concentrate the brush strokes along the lead lines rather than across. This will begin the cleaning phase and also begin to darken the came. Repeat this on the other side.

After a few turnings, most of the cement will be cleaned from around the leads. Don’t try to get all of it away, you will need that colour for polishing. The glass will be shining, and any felt tip marks you made on the glass will have gone too. Clean up the dust from the panel and bench in preparation for polishing.

Part 3