A Deep Dive into the Fisher Space Pen Refills

Let's take a deep dive into the Fisher Space Pen refills, their history, how they are made, the unique properties of the ink and what refills are available. 

A Brief History of the Fisher Space Pen Refills

In 1948, an inventor and pen manufacturer by the name of Paul C. Fisher founded the Fisher Space Pen Company in Chicago, Illinois. One of his first big breakthroughs, was the invention of the Universal Ink Cartridge - a refill cartridge that could fit most pen brands. This solved a problem for stationers, allowing them to reduce the number of refills they had to carry as previously they required 4 colours in 2 nib sizes for every brand. These universal ink cartridges are still available today.

Next, Paul Fisher was able to solve a problem for the astronauts. In 1966 he developed the Sealed and Pressurised Fisher Space Pen Ink Cartridge for the original AG7 Anti-Gravity Pen - check out the original patent drawing! The properties of the pressurised refill allowed the pen to be used in a zero-gravity environment - perfect for up in space! After 18 months of rigorous testing, the AG7 with the Pressurised Ink Cartridge made its debut into space on the Apollo 7 in 1968. The Russian astronauts soon followed suit and exchanged their pencils for AG7s too. 

2016 marked the 50th anniversary of the Fisher Space Pen Cartridge. To learn more about the history of the space pen, the pressurised refill and Paul C Fisher, watch Paul's son, Carry Fisher, tell the story.

What makes the Pressurised Ink Cartridges so special?

The magic that allows pens with Pressurised Ink Cartridges to be used in a zero-gravity environment is in the thixotropic ink and the pressurised nitrogen gas that uses a sliding float to push the ink towards the tip, rather than getting gravity to do the work (hence it's appropriate for use in space where there is no gravity!). The thixotropic ink changes viscosity from thick when inside the ink reservoir to a thinner viscosity when pressure is applied allowing it to flow through the ultra-hard tungsten carbide ball to write on paper at any angle and in most conditions - zero-gravity, underwater, over oil and grease, in -45 to +120 degrees Celsius, and three times longer than the average ballpoint pen.

Anatomy of a Pressurised Ink Cartridge:

Interested to know how a Pressurised Ink Cartridge is made? Take a look at this fascinating video:

Types of Pressurised Ink Cartridges

There are three types of pressurised ink cartridges that we will look at the details of: The PR - Pressurised Ink Cartridge (pictured in the middle), the U - Universal Ink Cartridge (top) and the C - Fisher for Cross Cartridge (bottom). The PR Cartridge comes in the thickest at 5.8mm. Alone it's 89mm long. Adding the plastic adapter for a Parker Pen makes it 99mm long. The U Cartridge is 2mm thick and at full length is 96mm. It has indents at the 87mm and 67mm marks. The C Cartridge is 3mm thick and 115mm in length.

Pressurised Ink Cartridges (PR)

Pressurised Ink Cartridges come in a variety of tip sizes and colours. They are suitable for the below Fisher Space Pens and also come with a plastic adapter that allow them to be used in Parker pens. You can shop them here.

• Bullet Space Pens
• Cap-O-Matics / Retractable Pens
• Astronaut / Shuttle Pens
• Backpacker

Fine = 0.9mm. Medium = 1.1mm. Bold = 1.3mm.

Universal Ink Cartridges (U)

The unique thing about the Universal Ink Cartridge is the indents that allow the cartridge to be shortened. The Universal Ink Cartridge (also pressurised) contains a much smaller amount of ink compared to the Pressurised Ink Cartridge - they write about 1200 feet depending on your writing style, as compared to the regular PR Cartridge which should write more than 12,000 feet depending on style and surface. The only Fisher Space Pen that takes the Universal Ink Cartridge is the Q4 Multi Action Space Pen. Only available in a fine (0.9mm) tip in Blue, Black and Red. You can shop them here.

Fisher for Cross Pens

These refills are designed to fit Cross style pens giving them all the benefits of a pressurised cartridge. As with the Universal Cartridges, these contain less ink than a standard Pressurised Cartridge and write for about 2400 feet depending on your writing style. Available from Little Inkling Co. in blue and black, fine (0.9mm) and medium (1.1mm). You can shop them here.