How Durable Is Your French Press?

One of the most frequently asked questions we get here at Planetary Design is “Why do you make your products out of Stainless Steel” or formatted slightly different “Why did you choose a stainless steel French press over glass or plastic”?  In a sunflower-seed-size nutshell, the answer is: durability, heat-retention capabilities, and non-toxicity. For the walnut-size-nutshell skip down to the paragraph starting with “In a nutshell”. For the slightly longer, but considerably more educational, version continue on.

Let’s start at the beginning. What is stainless steel? We’ll assume a fundamental definition of steel as a hard alloy of iron, carbon, and an array of other elements. So what differentiates “stainless” steel from other steels? All stainless steels share a minimum percentage of 10.5% chromium. It is this element that reacts with the oxygen in the air to form a complex chrome-oxide surface layer or “film” that is invisible but strong enough to prevent further oxygen from “staining” (rusting) the surface. So literally, stainless steel doesn’t stain or rust. The chromium-rich oxide film is also unique in its Harry Potter ability to self-repair. So even when the film is denuded exposing the steel to the atmosphere, it quickly fixes itself…. It’s pretty much magic.

Stainless steels are further broken down into 3 main categories and this gets pretty chemically complex but the simplified version is this:

1. Austenitic – (generally what knives, pots, pans, French Presses, and even Grandma’s hip replacement is made from) – contains iron, carbon, chromium and nickel, and sometimes manganese and nitrogen. They are most notably the 302 composition of 18% Chromium and 8% nickel (anti-corrosive) as well as the 304 surgical stainless steels containing 18-20% chromium and 8-10% nickel. So 302 and 304 are what we generally see on the retail market. Austenitic is what we’ll focus on as this is where our AirScapes and French Presses fall.
2. Ferritic – contains iron, carbon, and chromium (no nickel) which means Ferritic stainless steels will be more apt to corrode and rust. This no-nickel steel is classified in the 400s.
3. Martensitic – these low-carbon steels are also nickel-less steels composed of iron, smaller amounts of carbon and around 12% chromium. Martensitic will also be classified in the 400’s and like Ferritic are more apt to corrode due to the lack of nickel.

The other types of classifications are the 200, 300, and 400 series. Again, this is more in-depth than we intended to go but the overview is this:

1. 200 series stainless steels are less durable and more corrosive than 300 levels because manufacturers will often substitute manganese for the nickel. Though they are food-safe, technically they are not near the quality of 300 series.
2. 300 series stainless steels are often referred to as high-quality stainless steels and you’ll often see the marketing material read 18-8 or 18-10 (18/8 or 18/10) grade. This means that the stainless steel contains 18% chromium and 8 or 10% nickel. These are also known as Type 304 stainless steels and what we’re concerned with, given this is the steel we use in the making of our Planetary Design products.
3. 400 series as mentioned above are stainless steels without nickel. Nickel is the driving force behind stopping corrosion and rusting so its only place in the kitchen is the outside of the fridge because 400 series stainless steels, unlike 300, are magnetic.

Planetary Design products are constructed of austenitic, 304, 18-8 (18% chromium, 8% nickel), double-walled (and many vacuum insulated) stainless steel – it is often referred to as “restaurant-grade” given its use in the food service industry. We chose this particular stainless steel as it is incredibly durable, non-toxic, provides incredible insulation and won’t impart flavors (meaning you can store garlic in an AirScape, wash it out and store cashews in it and the cashews won’t taste like garlic). There has been discussion on the safety of stainless steel in regards to hot beverages given that a small percentage of the population is sensitive to nickel. However, many tests such as this 2010 Finnish Study have determined there is no significant leaching of the nickel and caused no reaction or any other kind of toxicity in the population. Especially when comparing stainless steel to plastic, especially plastics containing BPA – Bisphenol A, (read this article from the National Institute of Environmental Health Sciences for more information and resources on BPA)  stainless steel is simply a far safer food and drink container. Hence, though it is a more expensive medium, it is far superior to glass and plastic.

Why not glass?

Glass is considered a very food-safe material and it’s fantastic in its recyclability and aesthetics but the proverbial buck stops there. Glass is about as fragile a material as there is out there. Meaning it breaks and/or cracks easily and not just from blatant drops but even from setting it too hard on a countertop or, more commonly, from tamping it on the side of the garbage trying to get the grounds out of your French press. Glass also fails when it comes to insulation. It simply cannot hold in heat, which is critical for both French Presses and mugs. Cold coffee and tea are great when they are prepared iced for that very purpose, not so much when they started hot.

In a nutshell (the walnut-sized version) Planetary Design products, including the Table Top Stainless Steel French Press are made from incredibly durable, highly insulative, 18-8 restaurant-grade, double-walled stainless steel. The double-walled feature takes the already superior insulative properties of stainless steel and, in essence, doubles it, though most studies will show more than twice the insulation. Many of our products are also vacuum-insulated meaning that between those double walls the air is removed. This removal of ambient air further negates a transfer of heat from the inner wall to the outer wall (since there are little to no atoms and molecules for the higher energy electrons to transfer to) making the already superior stainless steel and double-walled properties even more superior. The durability of stainless steel from both long-term use and short-term breakability standpoint leaves plastic and glass in the dust. Unlike plastic, stainless steel has also been found to be a very safe medium to store food and beverage in. So there ya have it: Incredible durability and superior insulation in a toxic-free and rather sexy looking vessel. This is why we manufacture the majority of our products with stainless steel.

Important Resources

• http://www.ttl.fi/en/publications/electronic_publications/documents/stainless_steel.pdf
• http://chemistry.about.com/cs/metalsandalloys/a/aa071201a.htm
• http://www.assda.asn.au/what-is-stainless-steel
• http://mightynest.com/blog/stainless-steel-all-about-food-grade-304-188-and-1810
• http://www.niehs.nih.gov/health/topics/agents/sya-bpa/