Lead and Copper Foil in the Same Panel

It is possible to combine copper foil in a leaded glass panel.

The copper foiled piece should be soldered before inserting it into the lead came. In this way the soldered together pieces become very like another piece of glass.

There are some special considerations, of course.

The copper foiled piece should be designed as though it were a single piece of glass and so can be accommodated into the surrounding pieces of glass. Copper foiled piece should not have severe undercuts which would make it difficult to insert into the surrounding glass. It may be necessary to incorporate a piece of the surrounding colour to make it fit into the panel.

The copper foiled piece should be finished with all the beads on both sides. If one side is left flat, it will collect water if on the outside, and catch on any cleaning processes whichever side it is on. However, the piece should be tinned only on the outer edges. This will ensure that the copper foiled piece will slip into the came.

The image below illustrates a copper foiled piece incorporated into a leaded panel.

This section of the panel shows the accommodation of the main leaded panel with the copper foiled piece with a line from a petal to a leaf. Otherwise, it was fitted as one piece.

Bulging lead panels

There is probably no means by which leaded glass, because of the innate character of lead as its skeleton, can resist its propensity to bend, bulge and sag. Evidence of these occurrences does not necessarily foretell disaster or immediate collapse. Bulging does not necessarily indicate the need for action or re-leading.

There are three basic stages through which stained glass passes on the way to requiring repair;
1. Bulging, bending and sagging
2. Loss of putty and breaking of solder joints
3. Unhousing of the glass from the lead


The points at which solder joints break depends on the materials used.

Since lead, compared with solder, is a resilient material abutting the more resistant solder, breaks will occur most frequently at the junction of the solder with the lead.

With zinc, the situation is reversed. The zinc is of greater resistance than the solder. As a result the break most often occurs on the solder at the point of the zinc junctions.

It is the very existence of resilience in lead which responds to the expansion and contraction of glass that permits the more healthy survival of the glass over the less sympathetic accommodations of either zinc or copper foil. Leaded glass, unlike any other medium, has the unique capability of having its skeleton (lead) replaced, when the need arises, without damaging its body (glass).

Butting of leads

Lead came is normally cut to meet up against the adjoining cames. This provides a neat joint that will carry the solder without needing to fill gaps. The easiest joints to make are those at right angles. You can measure or estimate the amount that the came must be shorter than the glass, but it is easiest to use a piece of came the same size as will be passing the piece you are cutting (gauge came). You centre the gauge came on the cartoon cut line near the joint. Using your lead knife you can extend the line of the side of the gauge came to the piece you will be cutting. The mark you make with the lead knife can then be used to guide your cut of the came, as you take it away from the glass.

Those joints with angles have the came marked and cut in the same way as for right angles as the gauge came will give you the correct angle to cut.

Always remember when leading that you lead to the cartoon lines not to the glass. If the glass is short, use the cut line to place the gauge on, not against the glass. If the glass is too large, adjust its fit.

Finger Protection While Grinding

Various methods of protection are used:
Finger stalls,
Taped fingers,
Altering the fingers used to press the glass to the grinding bit,
Gloves – but they have to very tight fitting to avoid getting caught in the spinning bit.
Duct tape,
Grinders' Mate.

Prevention
The sore fingers are usually caused by tiny cuts from the glass. So, all these methods are ways of putting something between the glass edges and your fingers. More importantly, you need to think about your practice if you are getting sore fingers while grinding.

The first thing is just to lightly grind all the way around the piece first. This can be quick, and should use minimum pressure. This will remove any sharp edges.

If you have to press hard to achieve the effect you want, it may be that your grinder bit is badly worn. It may also be that you need to have a coarser bit to achieve the amount of grinding that you need.

You should not be pressing hard in any case. This will wear out bearings on the motor and reduce the life of the bit. You should use medium pressure and allow the diamonds on the grinding bit to do the work. Fine work requires a fine grit, removing a lot of glass requires a coarse bit, not more pressure.

If you have to remove large amounts of glass, you need to review the accuracy of your cutting. You should not be relying on the grinder to do more than tidy your cuts.

Remedies
There are several remedies to relieve the soreness:

Cucumber melon antibacterial hand lotion
Vitamin E.
Tea tree oil
Germolene

Rebates in Stone for Leaded Glass

Side rebatesOne side of the rebate in stone should be deeper than the other. This allows the panel to be slotted in and then slid back into the shallower rebate. Which side the deep rebate is on is not important.

Adjusting the placement of the panelTo help move the panel from side to side stiff oyster knives and lead knives are important. This allows you to get behind the edge and slide the panel to the side, especially when it is sitting on top of another panel to make the fine adjustments to get the lead lines flowing correctly.

Top and bottom rebatesFor the top and bottom rebates it is important that the top is the deep one. You insert the panel up into the slot and let it settle into the bottom rebate. The panel edges should be completely covered by the stone.

Extra cameIn all installations into stone, you should carry extra came of at least 12mm (1/2”) to solder round the panel when the stone work is not as accurate as it should be, either through workmanship or weathering.

Wedges
Have some little blocks of wood and some whittling tool to hand to wedge the panel in till mortared. It is possible to use little scraps of lead for the purpose. These wedges don't need to be robust, they are just there to hold the panel in place until the mortar is in.

Mortars
Mortars for stone should be of lime cement, or sand mastic. Don't use silicon, you'll never get it out again! Also don't use putty as this stains some types of stone and the oils leech in to the stone, causing the putty to dry and therefore the window ceases to be watertight.

Dressing the Lead Came

If you have consistent difficulty in sliding the glass into the came, you should consider dressing the came before use. Dressing the came consists of running a fid or other hard material along each of the four flanges of the came. In doing this, you are pressing each flange in turn down against the bench or other smooth surface.

Dressing the cames gives a slight bevel or ramp for the glass to slide over the edge of the came and into the channel of the came. You can dress the whole length at once, or as you cut the pieces off from the main length. Dressing shorter pieces is less likely to bend the came.

Silhouettes in Leaded Glass

There are also times when you may want to have a silhouette, you can cut it out of lead foil and solder it into place. This allows intricate shapes to be made when a dark representation of the shape is required. If the panel can be seen from both sides, the overlays should also be on both sides. This can be applied to copper foil too.

Representing Acute Angles in Leaded Glass

False lines are used in leaded glass where the design calls for an angle that cannot be cut into the glass. This includes right angles and even more acute angles. E.g., the petals of a fuschia flower. The design would call for an angle of about 60 degrees. This is impossible to achieve through cutting. So the glass is cut in a curve and the cames on the side and bottom of the petal have their hearts cut out so they overlap each other. The overlap is then trimmed to the shape of the outside of the petal. When soldered, the appearance is of the glass being cut at the angle required for the flower.

Cartooning for Acute Angles

When you are designing panels, you can prevent some leading difficulties. If you have shapes that join at acute angles, you can alter the design to make the leading simpler.

Say you have two balls touching. You can design the panel so the cut lines intersect or touch each other. This makes for extremely acute angles in the cutting of the cames. Two balls touching in the presentation drawing will not look the same if leaded that way.  So if you make the edges of the balls just a few millimetres separate, the cames will pass each other, just touching, and so have the appearance of the presentation drawing, rather than the appearance of overlapping.

You separate the lines by the thickness of the came you will be using for that area. If you are using 6mm came, the cut lines should be just less than that distance apart. This will allow the cames to go around each shape and the flanges of the came will just overlap. This makes for quick leading and a clean appearance.

Copper Foil vs. Lead

The copper foil technique may or may not have been invented by Tiffany, but he certainly used it extensively in his studio. Thus it is often referred to as the Tiffany method.

It is neither easier nor more difficult than lead. However, it’s significantly cleaner because it does not involve the use of whiting or cement, which is why this technique is most often taught to beginners in North America. In Europe leading is most often taught first.

Some people deduce that copper foil must be stronger than lead because the solder goes all the way around and between each piece, but lead is still the preferred method architecturally, holding up huge weight-bearing windows for hundreds of years.

One thing copper foil can do, though, is allow stained glass panels to curve, as you can see in the multitudes of Tiffany lampshades that are still around today.

There are a few other differences from lead in the construction of copper foil panels. First, copper foil is less forgiving in that there is no channel to hide errors in glass cuts. Precision in cutting becomes especially important.

However, while cutting may be a little more difficult, soldering foiled pieces is a little easier because you can’t burn through copper foil the way you can through lead. If you accidentally apply too much heat, the solder just drips through to other side and forms a ‘mushroom’ that must be cleaned up later. Or it cracks the glass.

Finally, lead panels are usually constructed from the corner out (pieces of wood form an “L” shape and the panel is started in that corner and grows up and out). Copper foil panels are usually started inside a (temporary) wood frame that goes all the way round the panel, like a picture frame. You don’t need to start in one particular spot because the pieces aren’t going to shift within their frame.

Fixing the Final Perimeter Cames

When all interior leads are in place, the top edge came is cut to butt against the vertical side edge, using a small piece of lead the same size to act as a gauge. These edge cames should butt up to the came ends in the interior.

Place a narrow strip of wood against the top outside came and hold it in place with horseshoe nails. Check with a square or by measuring to be sure the just placed came is at right angles to the left side of the panel. Do the same with the other side.

If adjustment is necessary, firmly tap the wood batten with the hammer end of your lead knife to get it into position. Place nails to hold the cames in position and get ready to solder.

Cementing Brushes

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. 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 also. Most brushes will only last 5-10 uses, and as they are not expensive, should be easy to throw away.

Leading-Up Boards

It is often best to have a separate board to place on top of your bench to do the leading. This means that you can move the project if it has to be delayed while having to do something else.

Start with a work board that is thick enough to be relatively rigid, but is easy to put nails into. Plywood is a good, but relatively expensive board. MDF is heavy and difficult to nail, so avoid it.

You can either have two permanent battens about 19mm (3/4") thick strips of wood attached at right angles to each other in one corner, or you can attach them to the board as required. The permanent placement means you do not have to check the accuracy of the right angle each time you use it, but it does not allow easy adjustment for smaller or larger pieces than the battens will accommodate. The temporary solution requires checking the right angle each time you use it, but it allows you to place the battens over the cartoon at the appropriate distance from the battens without cutting the cartoon or multiple checks of the accurate placement of the cartoon.

The battens should be attached to the "base" board about 60mm (2 1/2") from the edge to have a little work area to cut leads, etc. They need to be a little longer than the dimensions of the pattern you are assembling.

If you are putting the battens on top of the cartoon, you can use the cut lines to align your battens. Cut two short pieces of the came you are using for the edge. Centre their hearts on the cut line and butt the battens against them. Nail or screw the batten in place. Repeat for the other side.

If you are using permanently fixed battens, place the cartoon, which has been trimmed to the outside lead line on two sides, against the wood strips. Use some horseshoe nails or tape to hold the pattern in place. Check to ensure the correct distance has been maintained between the battens and the cut lines on the cartoon. Adjust as necessary.

Now everything is ready for leading.

revised 26.4.24

In Situ Leaded Glass Repairs

Here you are, just beginning leading and some one asks you to repair their leaded glass window. But they don't want you to take the window out of the frame. They want you to do it in situ. There are some general guidelines on how to go about it:

• Gently remove the cement from under the came leaves. You can use most any kind of stiff blade. You don't have to get it all out at once. Just work round the whole piece of glass.
• With a sharp lead knife, cut diagonally into the solder joint until you are almost halfway through.
• With a stiff blade gradually work the leaf of the came upwards. A stiff oyster-type knife (properly called a stopping knife) works really well. Apply the pressure to the leaf of the lead came.  Try to avoid levering against the glass.
  
  
  
• Continue to gently lift the leaves of the came until they stand vertical almost back to the heart. This obviously is much easier on thicker came than thinner. I try to avoid doing any less than 6mm, and that is difficult. It is also more difficult to do with half round came than with flat came.
• With grozing pliers gently lift the solder joints. Be careful of the surrounding glass, so that you don't have to replace more glass.
• If you haven't already now is the time to tape the broken glass together.
• Work out the cement between the came and the glass. This should provide you enough space to work the glass out.
• In some cases the glass won't come out in one - taped together - piece. Now is the time to take a rubbing of the opening so you know exactly where the leaves of the lead came are. It provides a pattern piece.  Smash the glass out. Wear safety glasses and gloves.
• If the glass has come out in one taped piece, use it as a pattern. You can trace round it with a felt tip pen and cut inside the lines. Alternatively, put it under the new glass and cut, using the edges as the cutting lines. You can also make a paper pattern from the glass.
• Insert the replacement glass into the opening. Most likely it will not fit in some places. See if the lead came leaves can be opened a little more. Also mark where the glass is too large. You can groze the glass, or if you are near a grinder, grind off the "high" spot.
• Remove the glass one last time, and spread a film of putty on the outside came leaf.  Use a very little, because you can't get outside to remove the excess.
• Clean the glass and handle it so that no finger prints are left on the outside.
• Now that the glass is in the opening, begin to gently smooth the came leaves toward the glass with your stopping/oyster knife. Start by only gently changing the angle of the leaf. Any large movement of the leaf will greatly deform it and might split it.
• If the solder joints are still standing up, take your stopping knife and gently tap the end of it with a hammer. The stopping knife should be parallel to the glass. Any hard hitting will tear the solder joint from the lead. (If you were doing this on a bench rather than on a vertical window, you could heat the solder joint and re-solder without all the tapping.)
• Push stiff black lead light cement under the leaves of the came from both sides if possible. Clean off excess. Polish with a soft brush.

If there are lots of broken pieces next to each other, repair one at a time, as each piece of glass supports the other. Alternatively, take the whole panel/window out and do it on the bench.

revised 26.4.24