There are a number of challenges you may run into as a fabricator involving adhesives and seams. Many of them can be easily solved through double-checking manufacturer instructions and checking the adhesive for correct color match and shelf life before applying to the seam. The following is a problem one customer had with an edge build-up.
The customer recently asked, “Why do I always get a white seam line on my countertop edge buildup when laminating either 2-cm granite or quartz? It even happens if I use a black adhesive on a black stone. What is the cause?”
We refer to these lines as “train tracks” and they can be the result of a couple of different things occurring. If you were to examine the seam line under a microscope, you would see that the adhesive itself has not actually turned white; there are two separate white lines on the edge of the seam (hence the train tracks term).
We’ve found that the main cause for this is insufficient wetting of the quartz or granite surface caused by surface contaminants. Dust (if you are working with quartz) or a slurry of dust and water (if you are working with natural stone) is a part of what you are seeing. The dust or slurry from the material processing remains embedded in the surface and can cause these lines to appear. Eliminating as much of this dust or slurry from the surface prior to laminating will greatly reduce the appearance of “train track” lines.
To prepare the surface, we would suggest surface grinding the bond area (back of the sheets and lamination strips) with a fine grit diamond pad or wheel. Smoothing the scratch pattern that holds the dust residue will clean away the surface contaminants and make it easier for the adhesive to wet out the surface. In addition, smaller scratches scatter less light and reflect the actual color of the surface. (Even on a black surface, scattered light from a scratch pattern can look white or light gray). Chips along the edge of a lamination strip will also contribute to this scattered lighting effect. Using a cutting method that produces the fewest chips on the edge will greatly reduce the problems associated with these lines.
Finally, another consideration is the adhesive cure process. An acrylic adhesive will lose a small amount of volume during the cure, and it is important to be familiar with the expected cure speed to avoid premature tooling and handling. Keeping this in mind, you must also make sure to tool off enough of the laminated edge to account for adhesive shrinkage. If you fail to take off enough material when finishing the edge, lines may also show.
One way to check to see if you are doing this correctly is to run your fingernail edge across the finished lamination.
If you feel a click, then you may have done one of a few things. You may have:
• Starved the joint (not enough adhesive)
• Profiled the edge prematurely (the adhesive will shrink after tooling)
• Wiped the excess adhesive off prior to cure (leave the excess adhesive on the joint to cure)
After the fact, you may be able to correct these problems by tooling off material to bring the finished edge flush with the cured adhesive, but it is much better to avoid them in the first place.