Saturday, 17 September 2011

Leading Basics

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 put nails into, so avoid it.
You can either have two permanent battens of wood about 19 mm thick attached at right angles to each other in one corner, or you can attach them to the board as required for each project. 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 making multiple checks of the accurate placement of the cartoon.
The battens should be attached to "base" board about 60 mm in 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. 

Corner battens nailed down over cartoon and perimeter leads placed

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. 
Using piece of came to set the perimeter batten

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.
Establishing the Perimeter for a Window
The first thing to be established about the panel is the placing of the came that goes around the edge of the panel.
Make a straight cut across the outside came and put that trimmed end into the corner and along the vertical wood strip. The lead should be longer than the leading cartoon to accommodate the length of the upper horizontal. If it is even longer than required, the extra can be trimmed off after soldering. 
Came butted at corner
Next butt a trimmed piece of perimeter came along the horizontal wood strip. This one should be shorter than the cartoon. It should be shorter by half the width of the perimeter cames to allow the vertical came to butt against it. An easy way to do this is to use a short piece of the appropriately sized came. Place the heart on the cartoon cut line and next to the perimeter came. Use you lead knife to extend the inside of the came across to mark the perimeter came. 
setting for cutting the bottom perimeter came to length

Placing a piece of came to set the line for cutting
The reason for having the vertical cames running from bottom to top is that there is a fraction more strength in the heart of the came going all the way to the bottom of the panel, rather than resting on the flanges of the came.
These perimeter cames should be held in place with horseshoe nails. Try placing the nails only where a lead line will be soldered in order to cover any nicks the nails might make. Alternatively, you can place the nails at the ends of the perimeter cames to keep them from sliding vertically or horizontally.
Straightening the Came
Before using the came it is important to straighten it. This increases the stability of the came during the leading process. Most often nowadays, you use a lead vice. This operates similarly to a cleat on a sailing boat. The more strain that is applied, the tighter the vice grips the came.
You place the end of the came into the vice so that the came appears at the back of the vice. Give the top of the vice a firm tap with your pliers to set the teeth into the came. Grasp the other end of the came with the pliers, and put one foot behind you to brace yourself if the came does slip out of the vice. Draw the came toward yourself until you can see the lead is straight and any kinks have straightened. 
Short piece of came being straightened with lead came vice and pliers
Take the came out of the vice and keep it straight. You transport it by grasping each end and keep the came under tension until you get it to the destination. It is often easiest to cut the full length in half before moving it, as it will not then be longer than your arms can stretch.
Remember, this process is to straighten the came to give pleasing lines in the leaded panel. It is not stretching the lead. Stretching the came can weaken the lead.

Dressing the Came
This relates to how easy it is to slide the glass into the channel of the came and nothing about your clothing.
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 down against the bench or other smooth surface. 
Pressing the came flange down with stopping knife.  Each of the four flanges need to be treated in this way

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 away from the straight.
Of course, it is not enough just to dress the came at the start. There is an analogous procedure after the whole panel has been leaded, soldered and cemented.
In this instance the term ‘dressing the cames’ means to close or bend the leaves/flanges of the came toward the glass. This is done after the soldering and cementing is complete. It provides a neat rounded appearance to the lines, traps the cement you have already added, presents less area for the rainwater to collect, and makes polishing easier. It is also the time when you may break the glass by putting too much pressure on the glass, so be careful!
Dressing the cames at the finishing stage is done with an oyster knife or fid. It is often best to avoid metal and better to use wood sticks or plastic tools. The pressure is placed on the came rather than the glass. Run the fid lightly at a shallow angle along each flange of the came. It is helpful to use a finger of your other hand to guide the fid along the cames. You may want to do this several times, as repeated light pressure will cause the flanges of the came to move gently toward the glass with less risk of breaking the glass. This can only be done while the cement is pliable. If it is done after polishing, you will need to re-do the polishing, as it will make the edges of the came silvery rather than shiny black.
Cutting Lead Came
Cutting came is a gentle process rather than an abrupt chopping effort.
There are at least three kinds of implements in common use to cut lead came. 
Clockwise from the top: curved blade (pro), straight blade, lead dykes or nippers

Lead nippers or lead dykes
Lead nippers/dykes are a kind of adapted side cutters, used for cutting wire and by electricians. But leaded glass dykes have the bevel only on one side of the jaws, making them almost useless for anything other than cutting lead. This arrangement only crushes the lead on the cut-off side and also leaves a minimum of lead next to the back of the jaws.
To use them the jaws of the dykes are aligned in the same angle as the heart of the lead, cutting across the leaves of the lead. They do not cut from the top and bottom of the came. These are very quick for right angle or very oblique angles on the came. However they are of little use for acute angles.
Lead knives
For more acute angles, blades are more commonly used. These can be either straight edges or curved blades. The straight edge lead knives are essentially putty knives or stiff scrapers sharpened to an acute angle. This kind of knife is normally wiggled from side to side while applying pressure to work through the came.
Other knives are curved to make rocking back and forth easier. There are a variety of knives such as the Pro or Don Carlos. Some look more like a scimitar than a lead knife! These are used to rock along the line where you are cutting the came.
What ever kind of knife you are using, be sure to be directly above the knife, looking along the blade to ensure vertical cuts.
Of course, saws are sometimes used. The blade needs to be coarse toothed to enable the soft lead to drop out of the teeth. These saws can be hand held or table saws. Normally, it is quicker to use lead dykes or knives. However, if you are in production mode, a powered table saw may be worthwhile.

 Leading Procedure
Cut the leads exactly as the cartoon indicates. In other words, where one lines runs into another, that is generally a stopping/starting point for the came.
Always lead to the cartoon line, not the glass. This ensures accurate completion of the panel. If the glass is slightly too small, the cement will take up the gap (assuming the flange of the came covers the glass – if not, you need to cut another piece of glass that fits). If the glass overlaps the cut line, it needs to be reduced.

Placing gauge for cutting to length
Cut the ends of the came shorter than the glass. The best way to determine the extent of this is to place a piece of came of the dimensions being used for the next edge on the cut line. Use it to determine the length and angle for the cut. The object is to have each piece of came butt squarely against the passing came, to make a strong panel and to make soldering easier. 

Marking the came for cutting to length

Testing the length of the came

Leading the first pieces
After establishing the perimeter cames, place the first glass piece into the corner formed by the perimeter cames. Normally, you will be working from the lower left corner toward the upper right corner of the pattern if you are right-handed. The reverse is the case for left-handed people. Hold each piece of glass in place with some scrap lead and nail. The scrap lead will prevent the nail from chipping the glass. It's important all glass is held in place with nails so no shifting occurs while working in another area of the panel.

Fitting the Glass to the Cartoon
Often you find that the next piece of glass does not fit properly. Possibly it rocks a bit in the came’s channel. Possibly it is simply just a little too big.
Glass too wide and slightly angled along the long line
The first thing to do is to take the previously placed piece of glass out and remove the came, to ensure the previous piece of glass is not too large. The glass should not overlap the cut line. If you have drawn your cut lines to 1.2 mm you should see only the faintest line of paper between the glass and the dark cut line. 
If the glass seems too large, check that it is firmly in the channel of the previous came, as sometimes the glass catches on the edge of the came and does not go into the channel.
The next check is to determine whether the apparently too large piece of glass really fits the cartoon cut lines. Place the glass inside the cut lines. You should see a faint line of paper between the glass and the cut line.
When you are sure both pieces of glass are the correct size, put the came back between them and check again. If the glass is still too large, make sure the came butting onto the came separating the glass is not too long. This is a common reason for lead panels to grow beyond their initial dimensions.
If the glass is the correct size and the butting cames are correct, replace the came. Put the too large piece of glass into the came and position it so it has the best fit to the next cut line. Take a felt tipped pen and run it along the edge of the came, marking the large piece of glass. 
Marked glass with nail pointing to area too wide that needs reducing
Take it out and check on where the line is farthest from the edge of the glass. That is where you need to reduce the piece. 
Snugging the came to the glass
It is important to have the came fit snugly to the glass (assuming the glass to be the right size and shape). If it does not, the panel is likely to grow beyond the intended dimensions.

To ensure the came is tucked snugly against the glass, you use a fid of firm material (wood or plastic, for example) to press against the heart of the lead. You can press directly toward the glass, or make multiple passes along the length of the came to ensure the heart is touching the glass all along its length.
You should avoid steel tools, because you may cut the lead, and if the blade is wide you will not find it easy to fit along all of the curves.

Following all these steps in the process of leading should lead to quickly and accurately assembled panels.