Stainless Steel & The Barcelona Chair

The frame of The Barcelona chair is of course metal. The question is what metal. To the laymen this might seem to be a simple question, however it turns out to be a surprisingly complex one.

Each type of metal, like steel and stainless steel, chromed steel and aluminum - can be made in a large number of different ways. Blending the component elements of iron, carbon, nickel, chrome etc in different quantities, using different techniques creates very different results. The alloys produced by these different blends have specific characteristics suited to particular purposes.

Some are more brittle, some more pliable; some are easier to weld, others are less prone to corrosion and a host of other forms of deterioration. Some have a higher shine than others, others scratch more or less easily... and so the list continues in ever increasing layers of subtlety and technicality. Price and availability are also pertinent.

For each range of desired characteristics there might be one or a dozen applicable alloys. Marine stainless steel for example, has quite uncompromising requirements. It needs to be tremendously resistant to the corrosion caused by salt water, it also needs to be weldable, not brittle, but not too pliable. Lives depend upon its structural integrity and so standards must necessarily be high. Raw materials are expensive, and AISI grade 316 stainless steel is only produced by three or four countries, creating a certain scarcity that is in part responsible for the high price. However buyers of Marine grade stainless steel are less price sensitive than those of household grade stainless steel.

For Barcelona Chair frames - there is considerably more latitude with regard to these criteria. Certainly the steel must be weldable and not too brittle - but the stressors and weights that can be expected to affect a chair are considerably less extreme than those on the hull of a steel ship. The frame of a chair should not corrode - but it can reasonably be anticipated that it will never have to survive submersion in salt water for extended periods of time.

The question of price sensitivity is more personal. Most people purchasing an item like the Barcelona chair do not have access to information about the steel grade of one chair versus another - (even assuming that they knew that this is a variable to consider.) This variable is however one of the principal influences on the price of The Barcelona Chair.

This said, it should be noted that although chairs made from the higher grade steels are generally more expensive than those made of the lower grades - it does not necessarily follow that the most expensive chairs are the best. There are two reasons for this:

1) Within this context, Grade 202 might be considered to be lower grade steel, due to its relatively higher propensity to corrode. However, structurally 202 is entirely sound enough for this purpose, (and is well suited to the more technical requirements of the piece).

For a great many reliable and ethical manufacturers, grade 202 provides the ideal choice for chroming. Chromed steel is of course the preferred finish of many people (an entirely subjective matter and one of no structural consequence). Chroming affords the steel protection from the elements as well as giving it that uniquely silky shine.

2) Medium grade steels such as 302 are entirely suitable for this use. Indeed grades as low as 202 would in all likelihood be perfectly fine unless located in an area with exceptionally high humidity.

3) At the highest end of the price spectrum manufacturers may employ grades of steel that far exceed either structural necessity or aesthetic distinction. They do so to differentiate themselves from the lower priced competition.

For example most stainless steel watch straps are made of Ainsi Grade Stainless Steel Type 316L, however Rolex watch straps are an exception in that they use Type 904L. Clearly some markets are willing to pay for quality in excess of structural necessity. In part this may perhaps be an attempt to purchase peace of mind, (in the absence of due diligence perhaps) but for many it is simply an emotional decision to have the best that anyone can offer.

History:

Many prospective purchasers of the Barcelona Chair ask if the chair they are buying is \'authentic\' with regards to the original. Clearly they are trying to ensure that they end up with the best option available, however this is not the best question to ask to achieve that end. The original chair made by Mies and Lily for the exhibition, was a relatively low grade steel, with a chromed finish. Although stainless steel was invented at the end of the 1800s, and patented in 1913, it was not in wide spread production for some time there after - and no doubt was not an easily accessible option in 1929.

In 1911 Philip Monnartz reported on the relationship between the chromium content and corrosion resistance. On 17 October 1912 Krupp engineers Benno Strauss and Eduard Maurer patented austenitic stainless steel.

Similar industrial developments were taking place contemporaneously in the United States, where Christian Dantsizen and Frederick Becket were industrializing ferritic stainless.

However Harry Brearley of the Firth-Brown research laboratory in Sheffield, England is most commonly credited as the "inventor" of stainless steel, but many historians feel this is disputable. In 1913, while seeking an erosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a martensitic stainless steel alloy.

Tecnical Details:

Stainless steel is defined as an iron-carbon alloy with a minimum of 10.5% chromium.

Stainless steel gets its name from the fact that it has higher resistance to oxidation, rust and corrosion.

Different grades of stainless steel are resistant to oxidation associated with different types of environment.

Resistence to oxidation associated with air borne moisture is normally achieved with additions of a minimum of 13% (by weight) chromium - given average ambient temperatures and salinity, but may require up to 26% for more extreme environments.

This works in the following way:

The chromium forms a surface layer of chromium(III) oxide (Cr_2 O_3 ) when exposed to oxygen, however the layer is too thin to be visible, so the metal retains it smooth and shiny appearance. It is, however, impervious to water and air, and so serves to protect the metal beneath. Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is also seen in other metals, such as aluminum and titanium.

Nickel also contributes to passivation, as do other less commonly used ingredients such as molybdenum and vanadium.

Types of stainless steel:

The addition of nickel or manganese makes stainless steel non-magnetic and less brittle at low temperatures. This is called an Austenitic steel and is graded as a 300 series steel. Over 70% of total stainless steel production world wide is 300 series stainless steel. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy.

There are over 150 grades of stainless steel, of which fifteen are most common. The list below pertains only to what is useful or feasible for use in the manufacture of the Barcelona chair frame. and is not intended to be exhaustive.

200 Series austenitic chromium-nickel-manganese alloys

300 Series austenitic chromium-nickel alloys
• Type 301 is highly ductile, for formed products. Also hardens rapidly during mechanical working. Good weldability. Better wear resistance and fatigue strength than 304.
• Type 302 affords the same corrosion resistance as 304, with slightly higher strength due to additional carbon. For Example: The pinnacle of New York's Chrysler Building is clad with type 302 stainless steel.
• Type 303 is an easier machining version of 304 via addition of sulfur and phosphorus Also referred to as "A1" in accordance with International Organization for Standardization.
• Type 304 is the most common grade; the classic 18/8 stainless steel. Also referred to as "A2" in accordance with ISO - International Organization for Standardization.
• Type 309 has better temperature resistance than 304
• Type 316 is the second most common grade (after 304); 18/10 denotes 18% chromium and 10% nickel making this the most chemically stable (has the thickest passivation layer of the 300 series stainless steel options). Alloy addition of molybdenum prevents specific forms of corrosion. 316 steel is used in the manufacture and handling of food and pharmaceutical products where it is often required in order to minimize metallic contamination. It is also known as "marine grade" stainless steel due to its increased resistance to chloride corrosion compared to type 304. SS316 is often used for building nuclear reprocessing plants. Most watches that are made of stainless steel are made of Type 316L.
• Type 321 is similar to 304 but lower risk of weld decay due to addition of titanium.

400, 500 and 600 Series are not applicable for use in manufacture of the Barcelona Chair frame.

After the steel is made:

For the purposes of the Barcelona Chair manufacturer the alloy is milled into bars

Stainless steel can be re-finished by any jeweler and it is 100% recyclable In fact, an average stainless steel object is composed of about 60% recycled material, 25% originating from end-of-life products and 35% coming from manufacturing processes.

Stainless steel finishes:

With regard to the Barcelona Chair, only two standard stainless steel finishes are common - in the creation of that distinctive highly polished aesthetic appearance.

• No. 7 - reflective finish
• No. 8 - mirror finish