Hi. I would like to have new tiles over the old tiles in the bathroom. The old tiles are of glossy type. The first thing I did is I removed the gloss from them. I used an angle grinder with a diamond disc. You can see the results on the pictures. The new tiles are going to be 30 cm by 60 cm size. What worries me is that the old tiles would not hold the new ones as the glue under the old tiles is not equally and properly spread, but in chunks as you can see in the pictures (the glue is the white chunks). However, I must say that the old tiles seem to be attached well, they do not move and did not move at all when I was grinding. The primer I plan to use Mapei Eco Prim Grip. What do you think?