Most snowflakes form in clouds that contain both liquid drops and ice crystals. At most temperatures experienced by the clouds found around the edge of Antarctica there will be many more water droplets than ice crystals within the clouds.
The few ice crystals that are present within these clouds will grow rapidly until they are large enough to fall out of the cloud. The low temperatures found in the interior of Antarctica ensure that clouds forming here tend to be made up solely of ice crystals and within these clouds the ice crystals grow slowly.
The distribution of precipitation over Antarctica is very marked, with several metres of snow falling each year near the coast but the interior only getting an annual snowfall of a few centimetres, thus officially making much of the continent a desert. After the snow has fallen it will be redistributed by the winds, particularly in the coastal areas where the downslope katabic winds can be in excess of 40 kts for long periods of time.
When the snow first falls its density will be relatively low at around 300 kgm-3 (compared to solid ice which is around 900 kgm-3). With the passage of time it slowly becomes denser as the ice crystals grow and eventually it becomes solid glacier ice.