Glass or Ceramic?

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One of our designers here at LUNAR was recently working on a project that required a material with a cold, smooth, high-quality feel, and she asked me which was a more sustainable material, ceramic or glass. This is what I told her:

Glass: There are many different types of glass, but I’ll focus on soda-lime glass here, the type most commonly used in containers, windows, etc. Glass is heavy and often gets a bad rap for that, but if recycled properly it is one of the few infinitely recyclable materials in common use today. It is also one of the few materials with a well-developed recycling infrastructure in almost every developed country. It can be fragile, but can also be made to be durable with various geometries and wall thicknesses (think about how long old Coke bottles stay in circulation). Glass can be considered, for all intents and purposes, to be non-reactive, so it won’t off-gas or leach like plastics.

There are some pretty destructive practices involved in mining basic ingredients for the mass production of glass, but if the product is made from recycled glass, that is not a concern. There is also an issue with the extreme longevity of glass. You’ll see quoted here and there that it takes a million years for glass to completely biodegrade, but the actual time is much longer than that. The bottom line is that once we take minerals from the earth’s crust and transform them into glass, they’re basically glass forever. This is another reason that using recycled glass is very important.

The glass we have already created is not going anywhere, so we should make something out of it in order to reclaim this “technical nutrient”.

So the bottom line is that recycled glass is a good choice for a product that won’t be transported much, is not subjected to high impact, and is sold in a region that has recycling facilities.

Ceramics: There are many different types of ceramics, but I’ll just speak to clay-based ceramics here, which are commonly used for flatware, mugs, vases, etc. Ceramics have most of the downfalls of glass, but lack one of the most important upsides: ceramics cannot be recycled. They can be down-cycled, which involves grinding them up and dispersing the power into a slurry used to create other ceramics, but the resultant product is usually weaker than the original.

Glazed ceramics have the same chemical stability of glass (glaze is essentially, although not exactly, a thin glass coating over the ceramic). Ceramic also has the same extreme longevity issue as glass, which is why we keep digging up ceramic garbage that people tossed out four or five thousand years ago.

Ceramic is lighter than glass, but usually because it is porous. This means that to make products equally durable, you have to make them thicker so they often weigh about the same (compare a drinking glass to a coffee mug). One of the big benefits of ceramic over class is that ceramic is a good thermal insulator due to its porosity. It’s also very good with extreme changes in temperature (glass will break if the temperature on one of its surfaces changes much faster than the other).

So, ceramics are a good choice for an application that requires extreme longevity, good insulation, or excellent resistance to changes in temperature, but if you’re going for a cold, smooth, hard, high quality feel, I’d stick with glass.