( alternative to the time-consuming task of applying washes to panel lines and other small details found on Gundams and other model kits).

August 21, 2015
(Originally written on February 7, 2002)
By Jordan Connor

What am I talking about here?
This topic centers on Rapidograph Technical Pens, which are manufactured by a company called Koh-I-Noor. These are drafting pens that come with refillable ink cartridges and have tips that come in a variety of sizes. You can use the pens to detail very fine lines found on models. In addition, different colored inks can be used to vary around the colors that are applied. With proper care, this pen can last forever!

Where can you get them from?
These technical pens can be purchased from (good) Art Supply Stores. In addition, these pens can be obtained from some on-line stores, (like Dick Blick Art Supplies, found at

How much do they run?
These pens run between $20 and $30 each. The ink runs around $3.50 each.

Why use them?
From my experience, when building Gundams and other small models, these remarkable pens are great for detailing panel lines. With the Gundams, the highlighting of the panel lines works regardless of whether or not the model has been painted. The Rapidograph pen will work on virtually any surface, painted or unpainted. This is a VERY quick and easy way to "fill in the panels.”

This pen, (from my humble experience) seems to work best in accentuating panel lines and fine details found on models. However, you should experiment with it, along with other options that may be available for highlighting panel lines first, (as I did), and draw your own conclusions.

(In addition to using this pen to highlight models, I also use it for drawing).

A parts breakdown!
Before I go on, I will describe the parts that make up the Rapidograph pen. This way, you will have a better understanding of the pen in its entirety.

The Rapidograph is composed of the following parts. First comes the Cap, that's found at one end of the pen. It is composed of the cap "body" (that is off-white in color), an internally located Cap Button (that is color coded and indicates the size of the tip of the pen) and a clear Cap Liner. The Cap screws tightly onto the next component of the pen, which is the Nib (or point).

The Nib is composed of 4 parts: an outer casing, (that also screws off, revealing the remaining three parts), an inner, plastic case (that has a small, metal tip), a small clear plastic cap (that's located at the end of the case), and a small needle, (that's situated between the plastic cap and case).

The Nib screws into the Pen Body, which has attached to it a clear, plastic, ink cartridge.

The Pen Body in turn screws into the Clamp Ring, (which is also color coded and matches up with the Cap Button). The Clamp Ring in turn screws into the Pen Holder, (which is the long, off-white hollow body of the pen).

The Nib, in general, should never be taken apart. This is because its parts are very sensitive and can be easily damaged. If it is removed, though, you will be able to see the needle that's located inside.

This needle is the heart of the pen. It allows the ink to flow out. The needle is useless if bent. This is why I don’t suggest removing it from the plastic case.

Your Rapidograph pen works like an airbrush, because when this needle is pressed against the surface of the object, it allows the ink to flow.

Use of the pens - The Cons and Pros
There are a few cons and pros about the use of the Rapidograph pen. Lets explore the Cons first.

Even though there are few problems associated with the use of Rapidograph pens (other than their upkeep and cleanup), there nonetheless are a few things to keep in mind when using them:

A weak tip.
With the smaller sizes of Rapidograph pens, the metal tip becomes VERY WEAK! They will bend or become warped if too much pressure is applied. This doesn’t mean that you have to worry about it bending all the time when you are working with it. However, you should keep this in mind when it's being used.

I'd like to briefly discuss the general construction of these pens here. Rapidograph pens are not markers where there is a felt tip with ink in the cartridge. Also, they aren't ballpoint pens that have a rolling action to bring the ink out. Rapidograph pens can be thought of as being "pen airbrushes." There is a very small needle inside a long, (rather weak) tip. When you press the pen down, the ink starts flowing. You only have to touch the surface of the model very lightly to start the ink flowing.

If the ink doesn’t flow, this means that your pen is clogged. This may also occur if you've used your pen on a painted model. Remember, very small lines = a very small hole that can be easily clogged.

Some ways to unclog your pen are explained in the "Tips" Section found below. However, a quick thing that you could do is just wipe the tip off VERY GENTLY!!!! In general, a wet finger or paper towel will do the trick!

These are ornery pens!
I have used Rapidograph Pens for about 7 years now and I have noticed that they are very ornery little pens! In fact, when handled wrong they can be a bit messy.

The instructions indicate that in order to get the ink flowing, you must use a back and forth motion. This motion is great for getting the ink flowing. In fact, sometimes it will get the ink flowing onto everything!

In handling the Rapidographs, you should take care and watch how hard you “shake” the pens. NEVER shake them hard unless you want black ink everywhere. The ink is extremely messy and very hard to get out of clothing.

If the ink flow stops, try to clean off the tip to get the ink flowing again. Most of the time the problem is not that the pen is out of ink. The problem is that something is blocking its flow.

Another tad-bit of information on the pen is that it does not take well to being dropped. Even with the top secured on, if this puppy falls, be prepared to clean up some ink that will spill everywhere inside the tip.

The "screw-on" characteristics
This really shouldn’t be labeled as a “Con”, but possibly more of a "Caution" characteristic. Because of the way the Rapidograph pen is designed, all of the parts except the ink cartridge screws in place. This includes the cap.

I suggest that if anyone other than yourself is going to be using (or playing around with) this rather expensive pen, you should make sure they know the pen should be screwed together, rather than being pulled or pushed to open and close. TRUST ME! You do not want to have to buy another just because someone couldn’t figure this out. ?

Now, lets move onto the positive characteristics. This section may be a bit short when compared to the "Cons" listed above.

Highlighting panel lines
This is the main reason for this article. With the Rapidograph, there are many different sizes. Now, I don't suggest that you go out and buy a whole set of these pens (unless you have the budget for it). I suggest you get ONE at a time. I mainly use the 3X0 .25mm one. This pen has a band of light tan around its body.

This Rapidograph serves as a very fine detailing instrument. In addition, it can be used to fill in larger areas with ink.

The ink, when flowing correctly will fill in the cavity of a line with a very even and uniform coating of ink. Just give the ink a couple of seconds to dry.

On semi-gloss or gloss surfaces, you can clean off any fingerprints or excess ink if you make a mistake…just do it fast.

On flat-painted surfaces, you should give the ink another minute or so to dry, and be careful with the ink application. It is more difficult to remove excess ink off of a flat-painted surface than from a Gloss or Semi-Gloss painted surface. To remove the excess ink, you will have to sand or scrape it off with an X-acto knife. This will possibly damage your paint job. Also, it will add more time to a process that was supposed to SAVE time in the first place.

If you are inking a lighter surface, (which, for Gundams are usually White), if you don’t clean the ink off quickly, you will again run the risk of ruining your paint job, along with the possibility of ending up with a semi-grey look.

The ink is water-soluble initially. However, when it dries, it becomes waterproof. This is the case even when applied to a painted surface.

The Rapidograph pen works best on panel lines that are nicely recessed. This is because you can’t apply a lot of pressure when using the pen. Also, the tip of the pen may go outside of the lines otherwise. (It is a lot easier cleaning up excess ink if you have eliminated it in the first place - ?).

Highlighting other surface details
I added this section because there are a few “extra” things that you can accomplish with the Rapidograph. With Gundam models, some have “Vulcan Cannons” on their heads. These can be highlighted.

In addition, other Gundams have those little “arrow?” shaped pointy things on them; (ok, ok, ok…I will admit that I have never SEEN the Gundam series. I am just addicted to the models). These can be accentuated as well.

With your Rapidograph pen, you can fill these small areas in easily with a variety of different colors of ink. I mainly use Black ink, but any darker hue of the corresponding base colored region would be great for highlighting these areas. This characteristic is unique with the Rapidograph pen.

Another use of the pen is as follows. On certain models (like Gundams), sometimes there are deeply recessed panel lines. With these types, your pen may not completely fill in the sides of these lines.

What you can do is carefully - (and I do mean "CAREFULLY" here) - angle your Rapidograph pen so the long tip of the pen (or the Nib) touches the edges of the panel line.

With this procedure, ink will both gather at the bottom of the line, along with nicely "shadowing" the sides of it as well.

Ok, with the pros and cons out of the way, I'd like to touch base on how to clean your pen. Koh-I-Noor produces a cleaning solution, as well as a cleaning tool. They do work...I mean of course they work. However, the solution costs about $3 -$4 dollars. The tool, (which is basically a “specialized” ear cleaner…ewwww), costs about $9. HOW CAN I SAVE MONEY you ask???

Well I know the pens are expensive…but you want to save money too? Ok basically you don’t need the tool or the solution. The ink is water based, and even when it dries, it comes off with some good ole' Enzyme Catalyst, (which is regular old dish detergent). You can even get this stuff at a Big Lots Store, for 99 cents.

In cleaning my pen, I take it apart. As I previously mentioned though, YOU SHOULD NOT TAKE THE Nib APART!

For cleaning your Rapidograph pen, I suggest that you get some Q-Tips, paper towels, some dish detergent and a bowl, (preferably a dark one, because it very well may get stained by the ink).

I do all of my cleaning close to the sink, because again the ink is very powerful and will stain your hands, your clothes…err...pretty much everything on you…(you understand).

Put a little soap in the bowl and fill it with really warm water. Remove the parts that are dirty with ink. This will include the ink cartridge and the Nib. In addition, sometimes the cap will be dirty as well, (especially if you dropped the pen).

That little round key that came with your pen comes into the picture here. It is very important and should be kept in a safe place. Otherwise, you may end up using some fine-tipped pliers, (like I did), and you will probably mangle the top area of your Nib, possibly damaging the very expensive tip, (like I have)!

Use this key to separate the outer casing of the pen from the inner casing of the Nib. Take the outer casing apart and place all these pieces into your bowl of water. (This will include the Ink Cartridge, the Nib, and the other parts that had ink on them).

Let them soak for about 4 - 5 minutes. Then take them out (the Nib will still have ink in it) and place them on your paper towels. Dump the bowl and fill it up with water again, (this time without soap).

Place the parts back into the bowl and begin cleaning them with the Q-Tips.

I usually do this…for the ink cartridge, it’s easy to clean. Just take about 2 Q-Tips and clean out the inside of the Cartridge. It will clean out nicely. Place this on a your dry paper towel when finished cleaning.

For the outer casing, I use as many Q-tips as I need to clean it out. This is usually around 2 again. Make sure you get all the ink out of the grooves found inside it.

For the Nib, this is the a little bit trickier. If you opted to buy the cleaning tool, refer to its instructions on how to clean the Nib.

For those of us who saved a bit or money to buy different colored inks, run a little bit of water into the Nib. Face the top of the Nib up towards the flowing water and move the Nib up and down in the flowing water, in order to move some water through it. Then, turn the Nib upside down and watch all the water and ink that comes out of it.

Do this until only clear water comes out (with no ink). A good way to check to see if your Nib is clean is to touch the tip of it to your dry paper towel. If the paper towel just gets wet, then you're good to go. Otherwise, you should go back and repeat this cleaning technique, until you get all of the ink out.

Once the ink has been completely removed, shake it and carefully touch the tip over and over again (for a few minutes), to make sure you remove all of the water. Finish up by cleaning the outsides of the Nip with a Q-tip.

Dry off the parts to your liking and put the pen back together. Put new ink in and you can even use the paper towel to get your ink flowing again.

If you have a good ink flow that then becomes very light, don’t worry. There is still a bit of water in your pen. Just keep trying the paper towel method to get a good flow. Finally, screw the cap back on and you're ready to go!

All in all it should take about 10 minutes to clean your pen out and have new ink ready for more panel line detailing!

OK, this is the last section. These are just a few one-liners and some dos and don’ts to mention here to sum up this article.

Pen options
There are many Rapidograph Pens to choose from. They come in different sizes (and colors). Aside from spending about $70 - $100 on a pen set of 7 or more, you can also purchase the “Nibs” at about $11 each. All you have to do is replace the Nib and you have a completely different sized Rapidograph pen. The only thing different is the color-coated body and cap of the pens. All the other parts, with the exception of the Nib are universal. All parts on the pen are interchangeable.

Simulating battle damage - Fluid leaks
For Gundams as well as other models that have bullet holes or some other sort of damage that has occurred on them, you can make “seepage” from the damage holes. Just draw a drip like shape and fill it in. The nice thing is that in battle damaging your model, flat colors are generally used. However, the ink is shiny when dry, which more accurately simulates hydraulic fluid or oil leaks quite nicely.

Simulating battle damage - Burn regions & spark areas
This is another way to simulate battle damage on your model. You can put a few small, different sized dots around a spot that is mangled. This will resemble burns from sparks or a hot object.

This is used to simulate either spots where sparks could have “popped” out and burnt surrounding areas, or where the hydraulic liquid or oil could have spewed out. I mainly use Black ink for this, (which is the color that should be used on major damaged areas).

Care must be taken
Again, be very CAREFUL when using these pens! As previously mentioned, these pens are pretty ornery. However, as with anything, once you get use to the little bit of maintenance that they require, they can become a very useful tool in detailing models!

Different colored inks
As previously mentioned, there are numerous colors of inks available. Also, again they are water soluable. Because of this, you can create lighter shades if you desire. The colors that I can remember are Black, White, Red, Orange, Blue, Brown, Dark Red, Green and Purple. In addition, there may be others out there that I have not seen nor used.

If anyone has in questions and/or comments, please e-mail me at the address listed above. Also, if I left out something or you have a tip that you would like to share, my mailbox is always OPEN!

There will soon be some additional information on the use of these Koh-I-Noor Rapidograph pens in a weathering article that I am currently writing.

Until then, Happy Modeling!!!!

(Tips and Techniques Page)

Copyright © 2015 Anthony I. Wootson Sr. and Jordan Connor. No material may be reproduced without permission of Anthony I. Wootson Sr. Unauthorized duplication is prohibited.