(Also addressing the problem of cracked cells of glass in a stained glass panel – see end of post)
Cutting the Lead to fit the Shapes of Cut Glass.
The lead is an “H” shaped section made in various width sizes to fit the glass** and also provide if necessary, room for reinforcement. A piece of lead will generally be sold in lengths of about six to eight feet long (2m to 2.4m). These strips of lead are called “came“. They can be any width dimension from 3mm up to 12mm. I have in my storage a number of; 3mm, 5mm, 6mm, 8mm, and 12mm lead came.
- **Stained glass sheets are normally of thickness 2mm+ to 4mm. There is a “thin” form of stained glass sheet which is about 1.6+-mm thick, allowing for two sheets overlapping to be used, sometimes giving interesting colour pattern effects. The two overlapping sheets (approx. 3mm+ in thickness) still have to fit into the same channel of lead came.
- The “H” section of an 8mm came is dimensioned typically as say, a 1mm+ core, and two channels of 3.5mm in depth. If the core is slightly thicker then the channels will be slightly less deep. Keeping a check of dimensions is important.
Stretching the Lead ‘came‘
The first task after deciding to use a particular strip of lead came is to stretch it. The reason for stretching is that it realigns the metal molecules of the lead, which slightly stiffens and adds strength to the lead came. Before doing this it might be a bit too malleable because the smaller the cross section width of the lead came, the more floppy it is likely to be.
In some cases this stretching might increase the length of the lead came by another 6 to 9 inches (150mm to 230mm) dependant on initial length and cross-section. It is of course important not to overstretch the lead came, as this could actually disfigure its cross section which would weaken it, or it could actually snap it in two.
To stretch the lead came we have a handy tool called a clamp, where it is fastened at one end which is self tightening when under load from pulling. The other end is gripped in a pair of pliers by you, and you pull. You do this with every length of lead came you are going to use.
It is best to only stretch the lead came as and when you need it. Using some of the chosen cross section size, you cut off pieces. These are then shaped to your glass design by bending them around the individual cut glass shapes, trimming them to the correct length and cutting angle to make the butt joint with the next piece.
Cutting Tool and Cutting
To cut the lead it is best to use the cutting tool illustrated. This is designed so that the lead can be cut by applying pressure directly downwards which usually gives the cleanest cut (practice required).
Trimming and Angle Cutting
The tool is also shaped so that should the need arise to cut or trim the lead ‘in situ’, one is able to do this even in tight joint corners with the curved part of the blade.
Sometimes the end of the lead needs to be trimmed so that a perfect butt joint of the shape desired can be attained. This happens when say two or three pieces of of glass in the design come together to a point, causing some pretty tricky cutting and trimming.
Shaping
The glass shapes in the design drawn on paper should all fit together with a gap of about 1mm to 2mm between them. This gap is represented in the design by the thickness of the drawn felt tipped pen line. The line represents the thickness of the centre/core part of the lead ‘H’ section.
Taking a typical piece of shaped glass from the design; this is then used as a former for the lead simply by pressing it around the glass edge to acquire the shape.
Sounds easy. Quite often it isn’t quite as easy as expected. Considerable care is needed and persistence, to shape the lead around the edge of the glass; making sure that a perfect joint is maintained with the surrounding lead to the other pieces.
Joints
Perfect joints are created when the length of the lead cut off the came is done cleanly, including the end cutting angle of the ‘H’ section. The perfect joint is a butt joint that is cut accurately so that there is no gap where it meets the other piece of lead.
The butt joint
The lead will have to be cut to form a butt joint at many different angles with other pieces of lead. These joints are rarely at right angles. If you look at the pictures shown below you will see many different types of joint occurring at different angles.
Another Sort of Joint
It is also possible to tuck the lead of one size of came under the edge of another, which is not exactly a true butt joint.
This sort of joint does offer slightly greater strength in some situations. The lead which covers the end of the adjoining lead is caused to rise as a small bump.
Soldering this sort of joint can be difficult. It is not so easy to maintain a flat soldered joint doing soldering this way. (A flat soldered joint is the ideal joint visually. Soldering joints will be covered in a later post).
Clearly many of the joints have had to be cut to an angle other than a 90 degree right angle.
Building The Picture Panel
As seen in the photo above and also later in ‘Reinforcement’ below, the glass panel is gradually built by installing the lead to the designed picture pattern. To keep the stained glass in the glass cells in position, horse shoe nails are used to pin everything in place.
Using Pins
Pinning applies to the lead around the glass pieces and the reinforcement steel came. The lead is kept in place by using a small piece of broken glass in the lead channel and pinning this. This enables the lead to be pinned without any damage from the pin itself against the lead.
Gradually one moves across the panel setting all parts of it tightly into position with the pins. This is the construction boundary line of your sheet. As the part you are working on becomes held in place, the next pieces of glass (as a cell being installed) will hold the previous ones in position so the previous pins can be removed from these. Thus you work across the stain glass panel.
Spreading of the Lead ‘came’ ‘H’ Section
There are situations where the lead channel will need spreading apart. There is a tool for this. The off-white tool in the picture.
Stained glass sheets often vary in thickness, sometimes the lead ‘H’ section may need to be made wider to accommodate the edge of the glass plus cement (dealt with later). Generally it is important to reshape the lead came.
There will be a need for reinforcement in the design; that is the insertion of a steel came within the lead channel. Steel came (or copper, brass, or zinc) has a cross-section of approximately 1mm to 1.5mm x 3mm to 4mm. Steel came is usually 1.5mm x 4mm.
Strips of lead came should always be spread using a spreading tool. This is to set the space the glass edge fits in to (i.e. the channel in the came H section), to a consistent width, also to allowing the insertion of steel came if required. This spreading tool is also useful for helping to smooth out kinks or small bits of twisting damage to the lead.
Smoothing
Smoothing – The smoothing tool is the steel tool with the wooden handle in the picture above.
This tool is ideal for smoothing the lead came pieces as they are installed into the stain glass panel. This applies to all shapes, but especially to straight pieces of lead running through the design.
The eye picks up immediately any wobble in straightness of the straight lead pieces in the finished design. So it is very important to make sure that such imperfections are smoothed out and made completely straight.
Reinforcement
Generally, if the stained glass panel is over a certain size (area) of glass, and/or the proportions of it are long compared with its width, it would be necessary to provide strengthening to the designed glass panel. Strengthening should be done at a half way mark along the longest dimension of the panel across the shortest dimension of the panel.
I always include steel came to the whole of the perimeter lead (frame), to make sure that the panel cannot flex along its longest length. It is advisable to study your stained glass design to look for possible weak spots in addition to mid-way cross pieces or perimeter frame strengthening. If there are weak spots, change the pattern of the design or increase the size of the came so it can be reinforced.
The last thing you would want is any flexing in the finished panel, as this would put pressure or stresses across the glass in the individual cells of the overall panel design. If a panel flexes, it is likely that a glass cell(s) will snap or fracture. Cracks are ugly and completely unacceptable in a finished piece. This is a disaster that can be avoided, by taking care. (See “Repairing Cracked Glass” later.)
Initially in your design, reinforcement pieces will be designed in; so protecting the design from the outset. It is essential to allow for this and to install the steel came as the glass panel is made.
To the left hand side of the panel being assembled in the picture above, can clearly be seen a steel reinforcement came. It is vertical except where it has been bent round shape of the tree bough. This shaping was done to make the bough of the tree appear in front of the lead of the vertical reinforcement. This is at the point incorporated into the picture, where the reinforcement has to run. There was a lot of other reinforcement in this panel due to its size.
It is possible to buy lead came with integral steel reinforcement ‘built in’. However this does not allow you make choices about how you want to reinforce the lead work in you design. Also the only size I’ve seen for sale lately is 12mm.
The steel came reinforcement can be added to lead came of dimensions 12mm and 8mm. Any lead came smaller than this is probably not viable, purely because of dimensional sizes.
Dimensions
To clarify, with 8mm lead came as an example; if a piece of 8mm lead is being used and the steel strip is to be added to one side, the dimensions begin to get tight on that side. 8mm lead came has a 1mm thick centre, that leaves 3.5mm on either side to fit the steel reinforcement into, plus then, the edge of the cut glass.
So if the steel is 1mm that only leaves 2.5mm to accommodate the edge of the glass on that side. In actual fact, due to slight variations in thickness of both the centre of the lead and steel came, the glass may only have a depth of 2mm or slightly less, to fit in to. This means that accuracy in glass cutting and finishing, with the careful shaping of the lead to the glass edge, is essential.
6mm Lead Came
Reinforcement can be done with 6mm lead came as long as the glass piece and the lead are excellently cut and matched. After the reinforcement came is added there is only 1mm to 1.5mm of channel left in the lead to fit the glass into. The seating of the glass in the channel has to be perfect.
Reinforcing 6mm lead came with steel is not recommended. Inherent weakness could be incorporated into the panel instead of strength.
Repairing Cracked Glass
It is assumed in this section that the damaged panel is still in the making stage. If the crack glass is in a panel installed in a door, window or other framed position; then it must be de-installed if possible. Doing a repair successfully in-situ is improbable. It would take great skill I think, acquired over years.
If we imagine a crack in a cell of stained glass in the centre of a finished glass panel; trying to repair such a crack is never easy. There are a few options: –
- The first option is to look on the damage as a form of ‘patina’ (if its tiny); therefore do nothing to it.
- Dependant on the severity and size of the crack, the second consideration might be to use a car windscreen repair liquid to mend the crack. Some of these liquids may almost make the crack disappear (again if its small). I would recommend trying this as it is the least traumatic method for the glass panel. There are also other forms of glue for literally glueing the glass, which can work well for small chips or pieces of glass or straight line cracks. If it doesn’t work, you can always go on to the final method.
- Removal of broken glass. Finally trying to repair a crack will require the removal of the broken glass, which means folding back the lead. If the glass is not broken so that some of it has fallen out, then break the glass carefully to do this. Remove all the glass from the broken cell. To remove the broken glass will require the slow and careful removal of the cement holding it in place. (Remove some of the cement to ease the glass lose; not necessarily all of it at once).
- Damage to surrounding cells could occur if care is not taken. Once the glass is removed, the top side of lead surrounding the cell must be slowly folded back so that a new piece of stained glass can be installed into the cell. It is easy to crack the glass in an adjacent cell(s) when doing this. Folding back of the lead can take hours. Folding back the lead also enables all old cement to be removed.
Removing Part of a Soldered Butt Joint
The folding back of the lead is one part of the repair (see next). However at every joint or corner in the shape of the stained glass piece, is a soldered joint. The lead that has been soldered there may well need a cutting job to be done. The lead at this point is comparative very tough. But in order to install the glass, this soldered joint may (but not always) need to be got out of the way.
One way to do this is to melt the lead with the soldering iron. This takes real skill in not over-doing it, which if it happens will be very difficult to repair without it looking a mess.
Cutting the lead away from the soldered butt joint is another option. Sometimes it is possible to pare it away with a Stanley knife. Carefully. As usual the exercise is dangerous to the rest of the panel.
The method I personally have used is a machine called Dremel, made for model makers. This machine has all sorts of tiny attachments for cutting away material and smoothing and finishing the result. Again – care is required, but the result can be good to excellent. The new glass is then much easier to install.
Folding-back (for more detail see future post entitled “Stained Glass – Cost of Stained Glass Art”)
Folding back the lead will be essential for installing a new piece of glass that you will have cut out again to the same design as the old piece.
Once the cell is clear and clean; install the newly prepared piece of glass onto a bed of cement on the lower edge of the folded-back lead channel. Allow the cement to begin to set to a solid hardness that is still workable. You will need to have inserted spacers to hold the glass at the right level in this underside cement, much the same way a tiler uses them when tiling a wall.
Start to very very gently fold back down the top lead to hold the glass in place. Again you may need to use some form of spacer to ensure the glass is held in position. Use the steel smoothing tool to ensure a consistent level space above the new glass is left for cement, once the top side of the channel is folded down.
If you have had to machine the soldered corner joints – rebuild these by using a tiny piece of flat lead to the shape that has been removed, (glue it in place to stop slipping), then solder on to it. This avoids solder setting on the glass, which can of course crack it again.
Make sure that the folded-back lead is level, undamaged by this traumatic operation and still leaves a gap for filling with cement. Now fill the top side of the glass cell lead channel with cement.
Go to the underside of the panel and pare off any excess cement to produce a clean finish that can be allowed to harden slightly. Then turn the panel back to the top side. When the top side cement is hard enough, scrape off any excess to make a smooth filling in the channel of the lead. Tamp/smooth the lead channel front and back to squeeze out excess cement before final hardening. Leave to harden completely. Once hardened on both sides of the panel, clean off any left over cement from the glass cell and polish.
Job finished.
Cost
This sort of work is in my opinion is unpriceable. The replacement of glass can take many hours and the bill could be hundreds of pounds/euros for just a single small glass cell just dependant on the level of difficulty. In fact the smaller the cell of glass to be repaired, the more difficult the repair can be in some cases. Doing the repair is also fraught with danger to the rest of the panel.
See post entitled “Stained Glass – Cost of Stained Glass Art”
