In some cases (particulary with modern, faster, formulations) it can, actually projecting (powder/smoke) out of the holes but it is not usually an issue. When

In some cases (particulary with modern, faster, formulations) it can, actually projecting (powder/smoke) out of the holes but it is not usually an issue. When it happens is because the expansion is too fast (and consumes all the water available), making the grout itself fragile, with slower formulas, after the initial setting of the grout, you should water/keep the surface wet. It is surprisingly difficult to find actual videos of it working (most are just a set of photos) because it is very, very slow (between 6 and 48 hours, usually), here is one from one of the many producers: https://www.youtube.com/watch?v=CYAcHc9rP9o https://www.youtube.com/watch?v=CYAcHc9rP9o