In May newly fallen snow usually remains powdery for one or two days on north slopes, and even longer at high altitudes. But, in general, powder snow is the exception in May. At high altitudes you will find hard marble crust in the early morning. At lower altitudes you will usually find ‘film crust’ and ‘perforated crust.’ For the formation of these excellent running surfaces, see p. [414].
The main difference between marble crust on the one hand, and either film crust or perforated crust on the other hand, is that the former is too slippery to give the ski purchase, whereas film or perforated crust is a splendid surface for Stemming turns or Christianias.
As a rule, in spring one descends after the sun has softened the crust. Whether the original morning crust was hard and slippery, or covered by a film or perforated crust, does not matter once the sun has melted its surface.[24] In any case, there will be a period of ski-ing on Telemark crust (p. [415]). The main importance of film or perforated crust is its value when you have to begin a descent before the sun has softened the snow. I remember starting one morning just after the dawn from the Oberaarjoch. I intended to ski down to the Grimsel and thence to climb the Galenstock, and I hoped to go from the Oberaarjoch hut to the Furka between dawn and sunset, taking the Galenstock en route. It was obvious that an early start was necessary. At that date I had done little ski-ing in June, and I fully expected that the top slopes of the Oberaarjoch would be covered by very hard and slippery marble crust. To my great surprise the crust, though hard, was covered by a beautiful film of soft, transparent brittle ice. As the ski swung round on a turn, this soft film peeled away and rustled down the slope with a soft splashing sound. No surface could be finer. Straight running was absolutely safe on the even, unchanging gradients of those summit slopes. There were no hidden rocks or hidden crevasses to fear. The film crust was absolutely true. There was no risk of running into a soft sticky patch or a windswept pocket. One could run as fast as one liked, secure in the knowledge that at any moment one could stop by a long-drawn-out Christiania. On really steep slopes one could link a succession of sweeping Christianias, the loveliest of all conceivable turns, and on gentle slopes one could run straight. The soft film gave an excellent purchase and prevented the ski side-slipping helplessly as one began to turn, for the ski cut in under the film and peeled it away.
Until a man has skied down from some glacier pass at dawn on film crust he has yet to learn the best that ski-ing can yield. That run from the Oberaarjoch stands out as one of the finest runs of my life. The great charm of film crust is that fast running can be combined with absolute safety, for a dangerous fall is almost impossible on this surface. I remember that we took twenty minutes from the pass to the snout of the glacier, and duly arrived at Gletsch after taking the Galenstock en route before sunset.
Perforated crust is harder and firmer than film crust. On very steep slopes it is a little too slippery, but on anything below 25 degrees it gives perfect running.
In May film crust and perforated crust are common in the early morning, and marble crust is unusual. After fresh snow one finds all sorts of shades of snow from pure winter snow to film crust, but a few days of cloudless weather is usually sufficient to change powder into crust on all but very high north slopes.
June.
June differs mainly from May in that the snowline is higher and that winter snow is even more uncommon. Film crust and perforated crust is the rule at all save high altitudes and just after fresh snow.
As a rule the snow is even better in June than in May. The more frequently spring snow is melted and refrozen the better it becomes. Old snow that has passed through this process again and again acquires a granular and crystalline character. It does not melt so thoroughly. Provided there is no touch of Föhn in the air, it retains this crystalline form even when it is melted. In June the snow remains good for ski-ing much later in the day than in May, even though the sun is higher in the sky. In May the period of transition from wet snow to crust is very sudden. One moment the snow is wet and heavy, and half an hour later the first crust has formed. In June there is often a well-marked intermediate period when the snow gradually gets colder and more crystalline. This granular snow is very fast and very true, and suitable for every kind of turn and swing at high speed. On May evenings the soft crust is very pleasant, but it is a little too soft and the snow underneath the crust is a little too woolly; but in June when the sun goes off the slopes the snow becomes crystalline, cold, fast and just compact enough to prevent the ski sinking in too deep.
In June the lower limits of the névé often show signs of furrowing. The action of the sun forms ridges and furrows producing a wavy effect. These ridges are unpleasant to ski on or to ski over when the snow is hard, but quite harmless when the snow has begun to soften. On steep slopes the ridges run roughly parallel with the fall of the slope. On the level the snow is divided into numberless little hillocks with corresponding holes.