I explain the easiest, most reliable method for how to caulk concrete countertop molds or forms in this in-depth video.
Before watching the video, consider the benefits of caulking your molds. Caulking is important when using melamine molds, because the cut edges of melamine will absorb water and swell when wet or damp.
Even if there is very little swelling that could affect the shape of the concrete, the water absorption will affect the curing of the concrete on the edge, and discoloration will be visible. This is less of an issue if you are going to grind the entire surface of your countertop, or if the concrete is going to be patterned rather than a solid color.
In some situations, it is not practical to caulk. For example, in some 3-D molds, it is not possible to caulk inside small, intricate areas. In this case, it is best not to caulk anywhere, to ensure a consistent look.
If you do choose to caulk, the time spent watching this video will save you countless hours and increase the quality of your concrete countertops.