The Copper Foil Technique
Why Different Widths? The first, and maybe most obvious reason, is that glass still comes in different thicknesses. True, most standard glasses are 1/8" thick, there are still many companies making hand rolled glasses, mouth blown glasses, and glasses with different textures. If 1/8" is the standard thickness of most glasses, then 7/32" is probably the "standard width" copper foil, providing enough overlap on both sides of the glass to create a strong solder seam. Some glasses are thinner and a narrow foil provides the needed amount of overlap while other glasses are thicker and require a wider foil. The second and maybe less obvious reason, is that you want to create different width solder lines in your design. Aesthetically, smaller pieces look better with narrow solder lines, larger pieces with a bit wider line. Or maybe the design has lines, pieces or elements you want to accent or remove attention from. You can achieve these effects by changing the width of the foil which changes the amount of overlap and ultimately determines the width of the solder seam joining your pieces together. The most commonly found widths of copper foil tapes in your stained glass store are: 1/8", 5/32", 3/16", 7/32", 1/4", 5/16", and 3/8". Other available but less commonly found widths are 1/2", 6", and 12" See all different types of foil tape products for stained glass use at site sponsor, Venture Tape. Why Different Thicknesses? You may have notice that the foil tapes not only come in different widths, but also different thicknesses: 1.0 mil, 1.25 mil, 1.5 mil are the most common. Most beginners find the thicker 1.5 mill tapes easier to work with; it is less likely to tear and curl up as you wrap the glass. But thicker tapes can be more difficult to work into tighter curves without splitting and some people find it more work to fold and burnish down. This is where the thinner 1.0 mil tape may be easier to wrap and burnish. The 1.25 mil tape falls in the middle. In the end it comes down to what is easiest for you to work with. Why different colored backs? Originally, all copper tapes were copper colored, front and back. This was okay for opaque glasses where you don't see inside of the seams. But when used on transparent glasses or bevels you can look through the glass edge into the seam. If you left the solder its natural silver or applied a black patina to the solder seams this looked unsightly. Manufacturers introduced black and silver back foils to alleviate this problem. Now if you use a clear or translucent glass and intend to apply a black patina to the finished piece, you can use black back foil to make the seams match the patina. If you are going to leave the solder silver, use silver backed foil. If you are going to apply a copper patina, then regular copper foil. There is even a double silver tape, silver on both sides, you can use if you don't want to have to tin the edges of pieces you're not soldering together but want to look silver. See all the different backings and sizes of foil tape products for stained glass use at site sponsor, Venture Tape. What is the best way to apply foil?
The object of foiling is to center the glass piece on the
foil so that you have equal amounts of overlap, front and back. Peel back about
1/4 - 1/2" of the paper backing from the foil to expose the adhesive edge.
If you are right handed, hold the glass piece in your right hand. With your left
hand apply the sticky side of the foil to the of the glass while looking down on
the piece to make sure it is centered. Use the thumb and index finger of your
left hand to peel press the foil in place as you hold and rotate the glass
between the fingers of your right hand.
Once you have applied the tape you want to crimp it over the
edges. Carefully fold and push the foil flat against the front and back sides of
the glass using your thumb and index finger. Make sure to fold corners neat and
flat.
The last step is then to burnish, that is press and seal the tape firmly against the glass. You can do this using a fid, popsicle stick, plastic pen barrel or your thumbnail. What you want is to make sure the foil is firmly stuck to the front, sides, and back of the glass, removing any wrinkles and air bubbles. What you don't want to do is to over rub and stretch and pucker the tape and allow flux to get under it. If the edges of your overlap don't line up evenly, trim using a craft knife. This process is repeated for every piece in the project. What about foiling tools machines? There are many different hand tools and machines out there designed to help apply the foil evenly, automatically remove the backing, crimp and burnish. Check with your local retailer as often they have models in the classroom you can try out before buying. Remember, there is a learning curve for most tools! Most of the foiling machines accept 3/16", 7/32", and 1/4" foils. What are copper overlays? Overlays are used to add detail or special effects to a piece of glass. You can create them from foil tape or with either adhesive back copper sheets or thicker copper sheeting. Adhesive back products are cut slightly larger than what is required to execute the design. The backing is removed and the copper burnished to the glass surface. Draw the design using a fine line marker and then use a craft knife to cut and remove those areas where the glass is exposed. You can then bead solder on the design before or during assembly. If it is a large area, don't solder to much or long in one place. This can cause the overlay to lift from the glass or heat fracture the glass below. You can also create overlays and 3-dimensional adornments from heavier gauge sheet copper using either scissors or a craft knife to cut the design. The piece can then be tinned and soldered in place during assembly or if it overlays an entire piece of glass, foil it directly onto the piece and treat as any other piece as you assemble the project. What are mosaic tapes? These are a specialty tape used in mosaic so that the colors and textures are seen as if your glass were back-lit. They allow you to use such glasses as cathedral and wispy in cast stone projects, allowing the color of the glass to come out instead of being changed or muddied by the color of the cement. They have a highly reflective surfaces that bounces light back through the glass, like backing the piece with a mirror. They come in brass and aluminum with a high tack adhesive and are designed to be resistant to athe exothermic reaction of curing cement, and stay bright for the life of your cast stone project. You can find out more about mosaic tapes and other mosaic project adhesives at site sponsor, Venture Tape. Foiling Tips and Tricks
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You want to start
about 1/4" before any edge / corner (doesn't matter where you start on round
pieces!) and then work your way around the glass, peeling back the paper backing
as you go. Come around until you have overlapped your starting point or come to
the corner. Then either snip with scissors or tear off at the corner. 
If the foil
doesn't wrap the glass equally front and back, remove the bad section and
re-foil. 
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