Copper foil – to grind or not?

 

This is a question which always has two entrenched sides.  One for always doing it; one for grinding only when necessary for shape.

Some facts:

• The glue on foil is an impact adhesive.

• Impact adhesives stick most securely to smooth surfaces, and resins stick well to roughened surfaces.

• The adhesive is severely weakened by the heat of soldering.

It is a misconception that the adhesive on the back of copper foil tape is a structural element of panels. The adhesive is a temporary means of fixing the foil in place. The heat of soldering seriously degrades the adhesive. 

Therefore, the adhesive can only be a temporary measure to hold the foil in place while the came-like solder structure is created.

The structural element of copper foil panels is in the fin of solder connecting the beads on each side. This forms a came made of solder instead of lead. To be sound, there needs to be a domed bead of solder on each side with solder connecting them.

It doesn't matter in the long term whether the foil sticks well to the glass or not. Yes, it is easier to work if it does stick, but the strength remains in the came formed of solder.

Not every score and break is perfect, and often grinding is required to fit the pieces together. But when the score is exactly what is needed, there is no reason to grind it. The adhesive will stick better to the smooth than the roughened surface.

My conclusion is that it does not matter which side of the grinding issue you support. But why go to extra effort of grinding when there is no noticeable effect in the end? 

It is the came that is created by the fin of solder joining the beads on each side that provides the strength in copper foil panels.

Finger Protection While Grinding

 Grinding lots of glass pieces often leads to a number of small cuts on the tips of your fingers. There are several things that can be done to reduce these cuts and the tenderness that comes from lots of grinding.

Various methods of protection are used.

Altering the fingers used to press the glass to the grinding bit.

Gloves –  It is not recommended that you wear gloves around rotating machinery. There is too much risk of injury, even on a small grinding machine. Some of the alternatives to gloves include plasters (band aids), masking tape, electrical tape.

Finger protection you can buy include rubber finger protectors, finger tip pads, finger caps (as used in counting money).

Other tools are made to hold the glass such as the grinder cookie

and Nick's Grinder's 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. This can be quick, and should use minimum pressure. This to is to take the sharp edges off the glass.  You can do a simple, light grind all the way around the piece. This removes the extra sharp edges that often remain after breaking the glass.

You can go a step further and do a light arris around the piece. This is just lightly holding the glass at about 45degrees to the grinding bit and going all the way around on all sides. This does not take off the shape of the piece, but gives a more rounded feel to the piece.

An illustration of the effect of holding the glass at an angle to the grinding head, although it need not be so much.

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.  Let the grinder do the work. Many people seem to put huge pressure on the piece to grind away the waste more quickly, but this is actually counter-productive. Less pressure means less fatigue, less chipping at the edges, fewer broken pieces, and most importantly, fewer cuts to the finger tips.

You should use medium pressure to allow the diamonds on the grinding bit to do the work. This will be about the same pressure as scoring the glass.  Fine work requires a fine grit, removing a lot of glass requires a coarse bit, not more pressure.  

If you frequently 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
Vitamin E
Tea tree oil
Germolene
Antibacterial hand lotion 

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, or maybe it is simply just a little too big.  Wait! Don't adjust the piece just yet. It may not be the problem.

Checking

The first thing to do is to take the too-large piece of glass out and remove the came it fits into, 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 1.2mm (1/16”) 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.

If that piece seems too large, 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, check the length of the came. 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. 

Do not be tempted to start reducing the glass at the visible portion.  After all, you cut it to the right size. It may be that the fit under the came is not very good.

To check use a felt tipped pen (Sharpie) to run along the edge of the came, marking the too-large piece of glass. 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.

The nail points to the area that needs adjustment

When you have reduced the "high" spots on the glass so it fits under the came evenly along its length, you can begin to adjust the outer edge, if necessary.

Grozing

When leading, and often in copper foil, the easiest and quickest way to adjust the glass is to groze the glass to shape.  This is usually done with with combination grozing/breaking pliers.

Breaker-grozier pliers, or groziers, are pliers used by glaziers to break and finish glass in a controlled manner, a technique known as grozing. They are dual purpose pliers, with a flat jaw that is used for breaking out scores and a curved jaw that is used for grozing flares from the edge of broken glass. Both jaws are serrated for removing flares and tiny points of glass. Wikipedia

The technique is to use the pliers, curved sid up, with a rasping motion rather than gripping.  This removes small pieces of glass from the edge.  Sometimes it is necessary to turn the glass over and the the grozing from the bottom.  If larger pieces need to be removed, use the pliers curved side up still, grasp the glass and pull away.  This is easiest if a score is made in the glass at the correct line prior to grozing.

Occasionally, grozing is not as accurate as required and there must be resort to the grinder. 

Grinding to fit

In copper foiling, a considerable amount of work goes into getting the pieces to fit with just enough space to accommodate the copper foil and a thin space for the solder fin to join both sides.  This of course, promotes consistently narrow solder lines without the solder melting through to the opposite side.

Grinding to pattern

Many times it is necessary to grind to fit pieces together with this degree of accuracy.  Those who draw onto the glass or stick pattern pieces to the glass, often grind to the template or the drawn lines.  This can lead to inaccuracies in relation to the cartoon.

The object in scoring and breaking the glass is to be as accurate as possible.  This reduces the amount of grinding required.  It saves time. It makes the whole process easier.  Still, we all have to grind relatively often.

Grinding to cartoon

In my view, when grinding to fit, you should be trying the piece out against the cartoon, rather than the template or the drawing on the glass. This will tell you how well the current piece fits in with the rest of the pieces you have already fitted to the cartoon. 

The cartoon drives the assembly of the whole piece.  Thinking you can just make small adjustments as you work along, creates increasing difficulties in making the whole fit together.  If you follow the principle of fitting to the cartoon, you are judging the accuracy of the piece against the cartoon lines, rather than any template or drawing on the piece of glass.  This means that the fit will be correct and the whole will go together with the minimum of difficulty.