When I am laminating a 2-1/2" radius on an outside corner of a countertop, using contact cement, I often experience the laminate not bonding at the straight points. Some people like to fill these areas with Bondo or squeeze a little superglue in there to get it to bond. Why does this problem happen and what are the solutions? I am thinking about white gluing the radius areas only.
(Laminate and Solid Surface Forum)
From contributor J:
Your radius is not cut at 90 degrees. This causes the edging to track up or down. When you force it to go straight around the corner, this causes the gapping to occur. If you cut your corner with a router and template, these gaps will disappear.
The best thing to do is learn about how laminate reacts to heat. Purchase a commercial heat gun for about $100 to $125 (we have used Bosch for years, but there are other good brands on the market), and cut some scrap laminate edgebanding to the width that you normally use. We over cut the width by 1/8" of the actual core thickness. Then, using the heat gun, good gloves because the laminate will get hot, and safety glasses, start by heating the strips one at a time and watch the movement of the laminate as it gets hot. Laminate forms at approximately 315 to 325 degrees Fahrenheit. Some shops use a heat-indicating material that is brushed on the edge to indicate the proper temperature; however, once you become proficient with this procedure, you will learn to look for the characteristics that the laminate will exhibit when it "relaxes" and loses its memory from being manufactured. It is easier to observe the relaxation of the material when the edgeband is applied vertically and heated.
Once the material reaches the correct temperature, you need to work quickly to form the laminate to the core edge before it cools. This is when the gloves really help because the piece is hot. After forming the corner, keep moving with the rest of the edge keeping the laminate tight to the core. This will usually eliminate any need to clamp the corner as it cools. Do not hesitate to hold the heat gun on the edgeband too long on the test pieces, and make sure that they have adhesive on them so that you duplicate the actual results when laminating the core. Find out how long it takes a piece of laminate to blister from too much heat and then back off the amount of time the material is heated from your result. The actual process, when performed properly, takes a lot less time than it did to type this response.
Once you learn how to do this correctly, it can make a lot of difference in how you can sell tops to customers, by making the outside corner of any top safer in the traffic areas of the home, by eliminating any sharp corners that someone walks past. It also lessens the dents in your kids' heads as they grow up. And a final benefit is that it removes the dark line and area where the laminate can catch and break. We have all seen the broken corner of a countertop in a kitchen, store or office because the deck was laminated using a standard square edge process.