PENS & CHEMISTRY - MATERIALS

I’ve been thinking about doing a series of posts that brings together the two passions in my life: Chemistry (as some of you will know, I study Chemistry), and pens. But I held off on it for a very long time. I guess, simply because it required too much preparation work, and frankly there were a lot of things I still didn’t understand in my first years at uni. 

Chemistry isn’t everyone’s favorite topic, which is something I’m fully aware of. Yet I found out over the years of collecting pens and studying that there’s a lot of chemistry in pens and inks (well to be precise, there’s a lot of chemistry in literally everything, but I digress again…). So I thought it would be cool to show some chemistry that is relevant to our hobby. 

Before I start rambling, please don’t forget that this is supposed to be a fun post (the definition of ‘fun’ can be quite subjective), different from what I usually do. It’s not supposed to be a complete chemistry textbook, and I’m just a human so I can’t promise everything is completely correct. Secondly, I’d like to apologize in advance for throwing with terminology. Unfortunately, terminology is key in the way chemists try to communicate, so there’s no way to work around that. 

METALS 

As I mentioned, chemistry is usually taught in a complimentary way, establishing a base, and building up from there. Since we don’t want this to become a 1000 page textbook, I’ll only explain the interesting bits, if you really want to understand everything you’ll have to do some more reading. 

Something I have to start with, is mentioning that chemistry can basically be divided in two main categories: Inorganic and organic. Organic chemistry is carbon-based, which includes all living matter (and thus you and me as well). Inorganic is pretty much everything else. 

When I look at the pens on my desk, I see a lot of metals. Metals are part of the inorganic chemistry field. They are interesting for their durability, and thus the entire EDC hype of super sturdy pens is basically built around metals. Metals have a crystalline structure, which means the atoms are stacked neatly in a specific way. A model that explains why metals behave like metals, and not like a mineral (which is also a crystal), is explained by the model of the electron cloud. Each atom in the crystal is held in place by a ‘cloud’ of shared electrons that moves randomly throughout the metal structure. It's a simplified depiction, but it shows that the forces that make up the metal are more of an interaction, instead of rigid bonds. This explains why metals are malleable without breaking, and why they are good conductors.

Metals can be categorized as inorganic materials, and they are usually made up of the corresponding atoms. Aluminium is made up of aluminium atoms, titanium out of titanium atoms, and so on. Then we have things like steel, or brass, which are alloys. Simply put, an alloy is when you mix two or more metals together in a forge. Steel for example, is a mixture of iron (Fe) and carbon (C), stainless steel adds chromium or other additive metals to it. Brass, another alloy, is made up mostly of copper (Cu) and Zinc (Zn), there used to be a small amount of lead (Pb) in it, but these days lead is avoided because it’s not the healthiest.

PLASTICS

Plastics belong in the camp of organic chemistry. Basically, when you look at pens, everything that’s not metal is a plastic one way or the other. Plastic is a not-so-scientific name for these materials, but it has become the generalized name for them throughout the years. In fact, plastic is actually the term that describes a physical behavior where an object under stress is deformed. Using this term to describe the class of materials we’ll discuss in a minute originates from the fact that many of them have a ‘plastic’ behavior.

Now since plastic is such a generalized term, it covers an immense amount of ground. In pen-terms that means everything from ebonite to acrylic to ABS injection molded pens can be called plastic pens. This is an area where there’s a lot of discussion, stating a high-end resin pen is not the same as a cheap ‘plastic’ pen. Technically, yes they all have different chemical structures, but they are all pretty much the same class of products. 

Now what are plastics exactly? Plastics are polymers. Polymers are literally all around us: a bottle of water, the rubber eraser on your pencil, even the paper you write on, which contains cellulose, a natural polymer of sugar atoms (not the kind of sugar you’d eat, I hope). So to explain what plastics are, we should first look at what a polymer is.

The easiest explanation I could think of is a pearl necklace. A polymer is basically a pearl necklace, where all the pearls represent a smaller molecule that is linked together to form long chains. Some of these ‘necklaces’ can be over 1000 pearls long! Each ‘pearl’ molecule that makes up the chain, is called a monomer (mono being ‘one’, and poly meaning ‘many’)

I’ve already mentioned that organic chemistry comprises all living matter. Even plastics (which are not living for what I can remember) are actually connected to living matter, because they are largely made from fossil fuel. Fossil fuels are basically a soup of prehistoric life (dinosaurs and plants and stuff), which is pumped up from deep within the earth’s crust. This soup contains a wide variety of different molecules, all of which can be used for different purposes: gasoline, asphalt, but also the molecular building blocks with which polymers and other organic materials are made. All these molecules have one thing in common: carbon! Carbon forms the backbone of all organic chemistry, literally. Together with hydrogen, these are the two most prominent atoms that can be found in organic chem (along with oxygen, nitrogen, sulfur, phosphorus,… to a lesser degree). 

So let’s look at pens now. We have established a base that is necessary to understand what the plastic materials in our pens are, and now we can look at some examples. First of all, let’s look at the cheapest plastic pens. These are made by a process of injection molding. Injection molding basically takes a polymer that has been pre-made into small granulates, heats it up, so that it becomes almost liquid, and injects it in a mold that is shaped like the desired object (one way to spot injection molded parts, is that there’s almost always a visible seam, and a ‘nipple’ from where the material was injected in the mold). One of the most used polymers in this category is ABS, which is made up of three different monomers: Acrylonitrile, Butadiene and Styrene, the three pearls that make up the necklace. ABS is what the Lamy Safari, Kaweco Sport, and many other injection molded pens are made out of.

Polycarbonate is often used as a transparent material, but is also used for the ever-so popular Lamy 2000 (the material of the 2000 is actually called Makrolon, but it is essentially the same).

When we look at fancier pens, the production method is often different to begin with, with the material being shaped on a CNC machine from a solid cast rod, instead of being injection molded. This is mainly because you can’t achieve the same intricate patterns with injection molding. Different polymers are used here, for example acrylates are probably the most commonly used. Acrylates are very common in polymer chemistry, and can be had in an incredibly wide variety of shapes. In this case, PMMA or poly-methylmethacrylate is quite a common one.

Interestingly, materials containing acrylonitrile monomers are also called acrylates. For the sharp readers among you, this may ring a bell, as indeed this is the same monomer that can be found in ABS plastic. This should give an indication as to how much all of these materials are actually related, even though they may not appear alike.

Then we are left with the more exotic materials, like ebonite, or celluloid. Ebonite is actually rubber that has been heat treated with sulfur, and is also called ‘vulcanized rubber’. This process is quite interesting, because the reaction with a sulfur compound connects all the loose polymer chains of the rubber to form a strongly connected network of polymer chains.

Celluloid is actually a tricky one. Remember that I mentioned paper being a polymer? Well the cellulose from paper is actually also an important component of celluloid. Cellulose is chemically altered to yield nitrocellulose, which has nitro (nitrogen and oxygen) groups attached to the chains. Maybe not entirely unrelated, trinitrotoluene (better known as TNT) also has these nitro groups, and it's quite an explosive mess. Needless to say celluloid is a bit unstable. If you remember the scene of Inglorious Bastards where the cinema is destroyed in a blazing inferno of burning film reels… yeah those are also celluloid!

Many brands (often Italian pen manufacturers) use a material called ‘cotton resin’. This is actually more related to celluloid than you’d think. Celluloid is made from nitrocellulose polymers, cotton resin is made from cellulose (cotton, the same as that found in your clothing, is nothing more than cellulose). Of course we’re talking about different production processes and things like that, but yet again it goes to show how similar a lot of these materials are.

Maybe you’re wondering why I haven’t explained what the term ‘resin’ means? I mention it throughout this post, but frankly it’s not a correct term to use for the materials you see used in pens. By definition, a resin is the precursor for a polymer. It is in fact often just a liquid mixture of monomers that haven’t undergone a chemical reaction yet that links them together (curing). It’s an often-used term by brands and bloggers (me included), but technically it’s not correct. 

Now to end this -rather elaborate- post, there's still one important material that hasn't been mentioned: the illustrous 'Precious Resin'! Now of course I'm talking about Montblanc's proprietary black plastic they use for many of their pens, like the Meisterstück. Unfortunately, nobody knows the exact composition of the material, which is a shame because it often leads to discussion within the community. There's no way to give a final answer as to what MB's material is, precious resin or just plain old plastic, but we can speculate about it.

The answer is two-fold: In the Chemical jargon, precious resin is a plastic. Any man-made polymer material, be it precious resin, acrylic, ABS or polycarbonate,... is in fact a plastic. Even polymer materials based on natural substances, such as celluloid or cotton resin, are plastics. On the other hand, chemically speaking there’s an enormous variation between different materials that are categorized as ‘plastics’, and they all offer different characteristics. From a brand’s perspective, I think trying to step away from the term plastic has everything to do with semantics. Plastic sounds cheap, and thus an entire slew of other names is used to try to work around it. In the end, there's no need to talk crap about precious resin, but it also shouldn't be glorified. 

I think that's all I have to say! This has to be the longest post I’ve ever put together. I know it might not be the most interesting topic I’ve ever written, but from a scientists’ perspective I really wanted to write this post to clear things out, and I’m glad that I finally got to it.

I’d be really happy to hear from you what you think of this post, and if you’d like to read more posts like it (not that I plan on making this into a full-time scientific blog). If you want to read more about chemistry, I’d suggest Wikipedia (no, that’s not a joke). Wikipedia is actually a pretty reliable source for information on scientific topics, and it’s an immense catalog that offers the entire A to Z of the magical world of chemistry! If you want more information on materials for pens specifically, Richard Binders website has some really interesting reading.