Nathalie, Sabrina, Jean and I climbed Boum after Maupas from refuge du Maupas.
Because the refuge was full, we begined in the parking of Lis the long 2000 meters of slope to the Maupas. Little by little with patience and enjoying the landscape we reached the ridge NW without problems. The snow in the west face make easiest the rocky ridge (grade I, F) to reach the access to the summit. A short coulouir of snow of 35º (be carefull with the long fall of west face) was the final route to the summit (it's a easy chimney of I+, F.sup. without snow).
After a little rest, we walked the glacier of Maupas in direction of Boum. The descent was neccesary to the 2700m, entering in the col with Mall Barrat and getting the rock climb of ridge NE, normal route of Boum (P.D. inf.) with a short chimney of 2 meters of II- and some exposed climbs of I. The return was across the Lac Bleu, normal route of Boum from the north. The slope total was of 2400 meters, and we maked it in 11 hours and half.