Guide to keycaps


Keycaps are the physical keys that you press when using a keyboard. They are attached directly on top of the switch beneath. For mechanical keyboards, keycaps can usually be swapped, allowing you to customize the keyboard to your own needs and preferences. In this short guide, we'll take a look at the different keycap profiles, the methods and materials used in the production of keycaps, and how they can be colored. Finally, you get some tips on what to consider if you're looking to buy a new set.

Cherry profile.

SA Profile.


Profiles, rows and sizes

The profile defines the shape of the keycaps. For example, the touch surface can be square or rounded, slanted or flat. Some well-known profiles are Cherry, OEM, SA, XDA and DSA. OEM is the most common profile. Cherry is one of the most popular profiles. These two profiles are relatively similar. For a visual comparison and overview of the different profiles, the website keycaps.info is very useful! For more detailed information and illustrations, we recommend taking a look here.

A full size keyboard consists of 6 rows of keys. Most profiles (not all) uses different shapes across 4 rows (even though there are 6 rows in total). This means that every keycap in the two upper rows and the two lower rows, has the same shape. Hence there are only four different keycap shapes in a full size keyboard.


Row 4 contains the function keys and the number row (as hightlighted in the image).
Row 3 starts with [Tab] and [Q].
Row 2 starts with [Caps Lock] and [A].
Row 1 corresponds to the two bottom  rows on a keyboard. 

All keys in each row have the same height and slanted angle, but there may be differences in height and angle between the different rows. Some manufacturers name row 1 at the top and row 4 at the bottom - but the principle remains the same whether it goes from 1-4 or 4-1. 

However, there are profiles that uses the same shape across all rows, like the DSA and XDA profile.


The size of each key are often named in units. 1u corresponds to the size of a single alphanumeric key (those keys that hold all the letters of the alphabet). The spacebar is usually 6.25u in size, which translates to 6.25 times larger than a single alphanumeric key. As a rule, most keys have their default size, but some keys are used slightly differently depending on the layout, e.g. for [Shift] and the control keys [Alt], [Fn] and [Win/Command].

Different materials

The most common materials used in the production of keycaps are:

  • ABS (acrylonitrile-butadiene-styrene) and
  • PBT (polybutylene terephthalate)

These materials have different properties that can affect the lifespan and feel.

ABS is usually the cheaper option and comes in a variety of different colors and patterns. With ABS it's easier to produce bright colors like bright yellow and bright green. In general ABS keycaps have more colors to choose from. However, ABS might wear faster than PBT and can also become slippery and shiny over time. Grease marks tend to show up more easily on ABS because the surface is often (not always) smoother.

PBT is known to be more durable than ABS, and has a more matte and textured surface. PBT keycaps is more difficult to manufacture and are for that reason often more expensive than ABS keycaps. PBT is more resistant to wear and tear and can retain its matte finish even after prolonged use. With PBT there are often less colours to choose from, and the colours can appear more dull. 

You'll sometimes stumble upon keycaps made of wood and metal. These materials provide unique looks but are not as common as ABS and PBT, and far more expensive.

Production methods

There are several different production methods for keycaps. One common method is injection molding, where the plastic material is injected into a mold to create a perfectly shaped keycap. Other methods include turning, where the keycap is cut out of a piece of material, and mold casting, where the plastic is poured into a mold.

Double shot injection is a manufacturing process where two different plastic materials are injected into a mold to create a single keycap with two different colors or textures. First, one material is injected into the mold and this forms the base of the keycap. Then the second material is injected into the mold around the first material, creating a surface that sits on top of the first material. The result is a keycap that has two different plastic materials integrated into one unified part. The advantage of this production method is that the legend (inscription) on the key is part of the key itself. In other words, it is impossible to wear away the legend on double-shot keycaps. Currently, ABS is the most commonly used material for double-shot injection, as manufacturing in ABS is both simpler and cheaper.

Design and colours

Dye sublimation: This is a process where a design is applied to the keycap using heat and pressure. First, a design is printed with special ink on a transfer film, which is then placed on the keycap. The keycap and transfer film are then subjected to high heat and pressure, which causes the ink to sublimate (change from solid to gaseous form) and penetrate the keycap. The result is a color-fast and durable design that sits inside the material.

Reverse dye sublimation: This is a similar process to dye sublimation, but instead of just dyeing one or more legends on a key, the entire surface of the key is dyed, except for the legend itself. 

Pad printing: This is a method where a keycap is stamped with a design. A silicone pad with the design is pressed down against the keycap and ink is transferred from the pad to the keycap. This provides an accurate and durable application of the design, but limits the possibilities for complex designs.

Laser etching: This is a process where a design is burned into the surface of the keycap using a laser. The advantage of this method is that it provides a high level of detail and the ability to create intricate patterns and designs, but it is limited to creating single-color designs.


GMK

You may have heard of GMK Keycaps? GMK Electronic Design, a German manufacturer, aquired in 2011 the rights and tooling (molds) to produce the original Cherry MX keycaps. The demand for these keycaps has exploded since then, and GMK is now the most sought-after brand in the keycap category.

But what makes GMK so special, why are GMK keycaps so expensive, and are they worth the price?

What sets GMK apart is their adherence to the original Cherry profile. GMK keycaps are often considered the benchmark that many others strive to replicate. GMK keycaps are made of ABS plastic, which is cheaper and less durable than PBT plastic. But they are "double-shot" - a complex and expensive production method that guarantees high quality (see section on production methods). And with production happening in Germany, it is reasonable to assume that labour and production costs are higher than in other countries such as China. GMK keycaps are often produced in limited editions, and when this meets high demand, prices increase accordingly.

The value of GMK keycaps is indeed a subjective matter, heavily dependent on individual preference and context. There are pro's and con's with GMK as well. Objectively speaking, as a first-time buyer, there are certain things you should be aware of.

Pro's:

  • GMK has the original Cherry profile
  • With double-shot keycaps, the legends will never wear away
  • The double-shot method produces keycaps with crisp legends
  • ABS plastic can be given strong and vibrant colors
  • High resale value
Things to consider:

  • ABS plastic wears out faster than PBT, and becomes shiny after a long time of use
  • ABS plastic can fade and become brittle during exposure from sunlight
  • 1.5mm thick ABS gives a relatively flimsy sound profile (which many also prefer)
  • High price

Tips before buying

If you've found a set of keycaps you like, you may want to check the following:

- Are they compatible with your switches? If you have switches in Cherry MX design, the keycaps must be compatible. Look for statements such as "fits all MX switches or equivalent clones".

- Does the set contain keys that fit your keyboard layout? If you see the overview image of all the keys in the set, you will easily be able to tell which row the different keys belong to. Usually the alphanumeric keys will have their natural position, but for control keys such as [Alt], [PgUp] and [Shift], it's a good idea to confirm that they have row numbers and sizes that matches your keyboard.

- Are they compatible with ISO or ANSI? If you have a keyboard with an ISO layout, you should make sure that there are keys that support this layout. For example, ISO has a large [Enter] key and a narrower [Shift] key than an ANSI layout.

- Are the legends transparent or not? If your keyboard has RGB backlighting, and you want backlit legends, make sure that the legends are transparent.

- What sound profile do you want from your keyboard? Generally speaking, thick and/or high keycaps will produce a deeper sound, while low and/or thinner ones will produce a brighter sound. ABS is a softer material than PBT, which is relatively hard. This will also affect sound.