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Rime Ice, Glaze Ice & Hail Rings

Rime ice and glaze ice are very much the same, after all the name implies that they are both types of ice! However, they form in different ways and look different and thus have different names. But keep in mind we're just talking about ice here, with fancy names.

Glaze and Rime ice form when a supercooled liquid water droplet hits an object that is below or near freezing (Click here for more on Supercooled water). Supercooled water drops can cause an ice storm as the liquid drops freeze on contact with the street, sidewalk, power lines, cars....basically anything that has a temperature below freezing. This creates a layer of ice and a dangerous winter storm, click here for a wikipedia article on the 1998 ice storm that shut down Montreal. The ice formed by the ice storm can be either rime or glaze ice. Rime and glaze can also form in more benign instances, like in the picture above where the freezing process was slow and allowed for dripping before freezing. Rime ice and glaze ice can also be found in hail! I'll explain, so keep on reading.

So what's the difference between Rime and Glaze?

Let's talk about the difference between rime and glaze ice. Rime ice forms when the freezing occurs rapidly. Rime ice is typically white or milky and is basically made of discrete granules. This differs from glaze ice which is more clear and in fact can also be called clear ice. Glaze ice forms when the freezing occurs relatively slowly, and the glaze ice tends to be harder and more dense than rime ice. Check out this picture below and see if you can pick out the layers of rime ice and layers of glaze ice?

The differing colors in a hailstone are due to tiny air bubbles trapped in the milky white layers of ice.

The milky white layers are often called "soft hail" because....well it's softer or less dense then the clear ice (I love it when things are simple to explain). The softer rime ice is formed in low liquid concentration when a supercooled droplet freezes quickly. The quick freezing process traps air bubbles in the ice, which is what gives the ice it's opaque and milky white appearance. In contrast, the clear ice (called hard ice) forms when there is a relatively high liquid concentration and the freezing process is slower. The slow freezing allows air to escape and the water to spread out around the object it is freezing on. When frozen, the lack of air bubbles and denser liquid concentration make this ice both clear and hard.

Each layer of the hailstone represents differing atmospheric conditions that the hail was exposed to as it developed in the updraft and downdraft of the thunderstorms. (For more on how hail forms, click here). Technically you could say the white ice is rime ice and the clear part of the hailstone is glaze ice.

Also, glaze and rime may look similar to frost, but frost forms when water vapor in the air (water as a gas that we can't see) goes straight from vapor to solid, so it skips the liquid phase. This is called deposition, as the water vapor deposits itself on an object as an ice crystal. The key is that it skipped the liquid phase. Glaze and rime ice do NOT skip the liquid phase. Also, frost is lighter, softer and typically has more of a feathery or treelike structure. Form more on frost, click here.