FAQ's
Q: What kind of resin should be used? Polyester (more common) or polyurethane?
A: Both resins have advantages and disadvantages.
Polyester is cheaper to laminate with because no special equipment is needed to mix the resin, and the material costs are less. You can mix colors into the polyester resin to create any color imaginable. Using polyester, many materials can be laminated between the glass, like rice papers, fabrics, organic materials, and metals. Normally, polyesters are best used in dry environments. However, they can be used for wet environments, as long as the edges are sealed and no moisture can penetrate them. Polyester shrinks when curing and can crack the glass if there is much difference in the interlayer thickness. Polyesters have a UV inhibitor that gives it a yellow tint, which can be noticeable if the interlayer if too thick or is laminated to a white glass.
Polyurethane, on the other hand, is more expensive to laminate with because special equipment is needed to mix the resin, and the material costs are more. It is difficult to add color to this resin, and only materials that are free of moisture can be laminated between the two glass panels. Once polyurethane is cured it is impervious to water, making it the perfect choice for exterior applications and even applications where the edge comes into contact with water. Polyurethane has minimal shrinkage and remains flexible when cured. Therefore, it is the best resin to use when there are great differences in interlayer thickness. When laminating materials that have different expansion and contraction ratios from glass, such as polycarbonates, acrylics, and metals, Polyurethane is best. This resin is the clearest.
Q: What kind of tape should be used?
A: Typically, a ¼” (6mm) tape is placed around the perimeter of the glass to contain the liquid resin between glass layers. The tape determines the thickness of the interlayer. A 1/16” (.06mm) interlayer is the minimum recommended thickness when laminating kiln cast glass. You may need a thicker interlayer, depending on the texture or flatness of the glass. The tape is most often black or white foam tape, but clear tape can also be used. If the finished glass will be captured in a channel, the tape will be covered and not noticed. If you want exposed edges in the finished piece, for best results, you will need to oversize your glass and have it cut to size with a diamond say or water jet. Some laminators may be able to do a tapeless lamination so the finished piece will have no tape between the glass layers around the perimeter.
Q: Which side of the glass should be laminated?
A: This choice will greatly affect the look of the finished piece. The shelf side (bottom) is the side most often laminated to because it is most often the flattest. If you laminate the shelf side it is important to realize that the resin will clear out any texture present so that the glass will go from translucent to transparent. If you don’t want to lose the look of texture, it can be sandblasted and sealed with a sealant to keep it from disappearing during lamination. You can also laminate to the face (top) of the piece to maintain the translucent texture. When you laminate to the face of the glass it is important to have it free from bubbles that are rising up from the surface. Also, if you are using a dam around the edge of the glass when you fuse it, the perimeter will need to be taken down. Both of these issues can be fixed with some coldworking. Laminating to the face can also be used to cover devitrification.
Q: To what sizes and shapes of glass can we laminate?
A: It is important that the two pieces being laminated are exactly the same shape and size. It is easier to laminate identical pieces, and the success rate in this situation is high. Laminating two different sizes and/or shapes together can be done, but the degree of difficulty will increase greatly, as will the failure rate. With liquid resin, almost any sized piece can be laminated. The limiting factors are the size of the laminator’s table, whether the resin is mixed by hand or pumped out of a machine, overall weight, and capability of the laminator. As for what shapes can or cannot be laminated, that depends, again, on the ability and knowledge of the laminator and which resin is being used. For complex shapes, most laminators would recommend laminating the basic shape and water jetting out the finished shape.
Q: Should holes and edgework be added before or after laminating?
A: If you are laminating your kiln formed glass to a tempered piece, it is necessary to have all holes and edgework done before lamination. It is imperative that all holes and edges on both pieces of glass line up exactly. This will guarantee that whatever needs to pass through the holes will fit and that the edges will line up. Unlike laminating with PVB films, once the glass is taped together it will not shift in the laminating process. For best results, you should consider doing a tapeless lamination if edgework needs to be done before lamination. When you are laminating two annealed pieces of glass together, you should consider doing holes and edgework after lamination. This will give you the cleanest and best looking finished product. You don’t have to worry about making sure that every hole and edge lines up perfectly. However, if you are going to water jet out the holes and edges, it is important to pre-drill a pilot hole anywhere a piercing will be made with water jet. You can’t pierce through the laminate interlayer without blowing out garnet and water between the two glass panels.
Q: How flat does the glass have to be?
A: No matter which resin you use, it is important that the glass sit flat around the perimeter and there be no low spots that would hold the perimeter of the glass up if it were sitting on a flat surface (like a piece of float glass). After adding taper around the perimeter of the glass to create the interlayer thickness, if there is any pressure where the two pieces of glass being laminated together come into contact (a bubble, for example) there is bound to be cracking as the resin cures. Cold working may be necessary to take down any high spots. If you want to use polyurethane, this step is unnecessary (Using polyurethane you could laminate glass with deep undulations to flat float glass). If the glass is not flat, but rather is bent is a radius, it can still be laminated if the two pieces are bent together so that they match. How tight the radius is and how many degrees (90* or 30* etc.) of the radius you are bending will determine how difficult the glass will be to laminate. Some shapes may be very difficult to laminate. When in doubt, consult an experienced laminator.
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INFO
Notes on Process with Glasslam* Polyester resin.
Considerations when laminating kiln formed glass.
Artists Release Form.