Gold’s most astonishing characteristic is its malleability (it does not work harden). In the (g)olden days, this feature was not of much use because it made gold too soft for manufacturing machinery as well as for fountain pen nibs because gold nibs would bend very easily. But because of its non-corrosiveness, it had been the only choice material for nibs (ink was even more corrosive than today).
Since gold by itself, it has not the mechanical stability or tensile strength needed for the task of writing; it must be mixed (“alloyed”) with other metals such as copper and nickel. The combination of alloying metals used determines the mechanical properties such as hardness and elasticity, as well as its colour.
Standard 14 carat contains 14 parts of gold, 8 ¼ silver and 1 ¾ copper. In the alloy for fountain pens, some of the copper is increased to 3 ¼ , silver is replaced by 5 parts of nickel and 2 parts of zinc. Nickel improves the hardness significantly. Vickers hardness of pure gold is about 30 MPa (Mega Pascal), that of 14-karat fountain pen gold is up to 200 MPa. And further to this, the nickel – gold alloy work hardens. A significant characteristic for manufacturing.
Nevertheless, from experience, I can say: gold nibs are much more prone to damage through being bent when applying excessive pressure during writing. It is also common knowledge amongst fountain pen users that gold nibs, generally speaking, respond more readily to increased writing pressure by widening the line.
Some like this attribute and choose a gold nib because it gives their writing more character. I mentioned this fact already chapter about the nib’s function.
Stainless steel as it is in use today was introduced between 1913 and 1935.
The type of stainless steel for producing nibs is called austenitic steel and is very similar to the well known 18/8 chromium-nickel steel.
In the EN-standard (European Norm), the name of this steel is X2CrNiMo18-14-3, a low carbon steel (X2) which increases its weldability, which is critical for the tipping process.
Its ASTM/AISI name is 316L. The German DIN calls it 1.4436.
The ability to work harden is its most significant quality. Its yield strength increases from somewhere around 240 MPa to 760 Mpa, which is essential for the elasticity of the nib. The hardening comes for free because during manufacture the steel is cold rolled into the particular cross section.
Annealed (soft) stainless steel of this type has a Rockwell C hardness of 10 and can be work hardened up to 32. This is less important for the writer, but significant for production.
Whether made from gold or stainless steel, each one of our nibs had an iridium bead welded on its tip to reduce nib wear through writing, and the friction between the nib and the paper. Casually, we call it Iridium, but actually, it is osmiridium, an alloy occurring naturally, containing 30 – 60% of the platinum group metal Osmium.
Referring to the Rockwell C scale, its hardness is 40, which makes it just a bit harder than hardened stainless steel. Therefore, cheaper pens still work reliably for at least ten years without an iridium tip for.
This tells you, that fountain pens from a reliable manufacturer are designed for much longer periods of usability. Iridium is at least ten times harder than gold, thus, as we would say today, a gold nib without a hard metal nib is practically useless.
At the time of early nib development, osmiridium had been by far the hardest metal available. It was also used as pivots in instruments and clocks. Fountain pen makers, like all artisans, are traditionalists and they stick to what they know.
Better pens use 14k solid gold points, while lesser ones use steel.
A common misnomer.
Let me rephrase this statement: More expensive pens often come with gold nibs. This gives them a greater perceived value, people are prepared to pay proportionally much more. The cost of gold nibs is about ten times higher than stainless steel nibs.
The internet told me that by far, most fountain pens at an average price (over $100) are equipped with steel nibs.
More crucial for reliability (if this means better) is, whether they are tipped with an iridium bead because this makes them last.
People say: “Gold nibs write smoother” or “they have more character”. If this means: the line width alters more readily due to change of pressure, then, the same can be achieved by a steel nib. If in doubt, visit the chapter Stresses and Strains. Anyone who calls himself a good nib designer or maker can design it and make to suit this purpose.
Concluding, I would like to boldly add one statement: after you have read the above, you know more than some nib makers. The proof is in the pudding, or, the nibs, which are attached to some fountain pens. If they would know it, I am sure they could make a better nib.
A better, a good nib does not cost a cent more, it needs more knowledge and care by the maker.