After the first try in making ridges, I experimented with a new technique. I used a bowl instead of a balloon. I put two layers of paper on the bowl, took it off and put two equidistant lines near the rim and freehand drew the ridges. That way, I was able to keep them evenly spaced. I also let it dry on the bowl so that the ridges would keep its shape and it worked. I also put the next layers of paper mache on the outside of the ridges, and when that dried, I put layers of paper in the inside of the bowl. I also made this a whole lot smaller than the first bowl. That helped a lot.