Guide to the Ultimate Filament Colorer technique

Context

In 2014, Mathew Beebe published something he called the Ultimate Filament Colorer on Thingiverse (but which I prefer to call the Beebe Colouring Technique because let’s get serious). It’s a technique of colouring plastic filament by passing it through the ink sponge inside a Sharpie marker before it feeds into the hotend of a 3D printer. The pigment mixes with the plastic inside the hotend, producing a permanent colour that doesn’t rub off. Beebe first did this with ‘natural’ (uncoloured and transparent) filament, and I later went on to document the results from white filament.

Benefits

There are many benefits to colouring printed objects in this way:

1. Space-saving! You don’t need to store lots of half-open spools of filament in different colours, and you don’t need to use them up even if you dislike the colour.
2. Cheap! You can get a Sharpie — and therefore a new colour — for about 1/10th the cost of a spool of pre-coloured filament.
3. Consistent results! Calibration is simpler because you’re using the same spool of filament for every colour.
4. Durable! The colour gets ‘baked in’ during the extrusion process, so you can sand and finish objects straight off the build platform.
5. Fast and easy! No need to sand, prime, paint, and seal your objects to get them fancy-looking.

In short, it’s a cheap set-and-forget way to start printing in colour.

Downsides

Of course, there are always some compromises with any technique:

1. PLA only (?). A redditor reported that contact with Sharpie ink instantly made his ABS too brittle to extrude. If you’ve used this technique with any plastic other than PLA, I would sure love to know.
2. One colour at a time. You can only print in one colour unless you swap out the Sharpie mid-way through a print, same as for any single-extruder printer.
3. Tricky to set up. Pushing the filament through the ink sponge takes some practice. If you try to stab your way through the sponge it will get compacted and it will be harder for you to insert the filament in the future. One of my markers is a write-off because I tried to make a pilot hole for the filament with a sharpened piece of wire. It simply compacted it like crazy and made ink drip out through the bottom. You need to be gentle.
4. You lose some filament. First you need to cold-pull once to get the majority of the previous colour out. Then you need to cut some filament off when forming a point for insertion into the Sharpie. Then you need to feed at least 20 cm through the extruder to flush the previous colour and get the new one going. Then when you swap to another colour, you need to cut the old coloured section off. I estimate that you lose about 40 cm of filament in total at every colour change versus 20 cm if you use coloured filament — but 40 cm is only 0.1% of a 1 kg 1.75 mm roll, so it’s hardly awful.
5. 1.75 mm filament only. Firstly, it’s hard enough to push narrow filament through the ink sponge. Secondly, 1.75 mm filament has more than twice the surface area of 3 mm filament per unit area, which means that there is less plastic to dilute the colour stuck on the surface.

How to do it

You will need:

1. A Sharpie. Maybe two if this is your first time.
2. 1.75 mm filament, either opaque white or ‘natural’ colour.
3. 2 mm drill bit (5/64 inch?) held in a hand drill or pin vise.
4. Small long-nose pliers. Don’t use round-nose jeweller’s pliers; they pinch the filament and create a weak point where it can snap.
5. Scissors or side-cutters.
6. Lighter or matches.
7. Optionally, a printed Sharpie holder.

1. Prepare the Sharpie

You need to pull the writing tip off with pliers and drill a hole into the opposite end of the marker.

2. Draw out the filament with heat

Wave your lighter underneath a section of filament while gently pulling on it. You don’t need much heat.

The filament will draw out into a long, thin section.

3. Cut a point into the filament

With your scissors or side-cutter, cut the thinned section of the filament at a very steep angle. The cut should be made very close to where the filament begins to narrow.

4. Insert the filament into the bottom of the Sharpie

Straighten about 15 cm of the filament and gently push it into the Sharpie and through the ink sponge. If you feel lots of resistance, back off, rotate the filament and marker a little, and try a different angle by bending the filament as you push it in to get the tip to move around. I have gotten the most success by machine-gunning this, i.e. doing the rotate-and-bend very quickly so that I can try as many angles and bends as possible in a short time.

5. (Maybe) force the filament out of the tip

If you really can’t get the tip to come through, then the filament has probably swerved and gotten stuck inside the head of the marker (the coloured part of the barrel).

Look down into the front of the barrel while moving the filament back and forth to see if the filament is indeed stuck here. If it is, great! Grab your long-nose pliers and use it to push the filament through while you rotate the marker.

Eventually it will come out.

6. Install in the (optional) holder

I printed these Sharpie holders to keep the Sharpie vertical above my extruder so that the filament could take a straight path through the Sharpie and into the hot-end. Each Sharpie goes inside a holder that was printed with its ink, so the holders do double-duty as colour swatches.

7. Install in the extruder

For direct-drive extruders like my Printrbot Simple Metal’s, you just feed the coloured filament directly into the hobbed bolt.

If you have a Bowden setup then you will need to come up with a spacer to hold the Sharpie and extruder apart so that the filament has time to completely dry before entering the PTFE tube. This should keep staining at a minimum.

Frequently asked questions

Am I really stuck with using PLA?

I don’t know! Lots of people have reported success with PLA, and one person has reported failure with ABS. As far as I know, no one has tried other plastics like HIPS, Nylon, high-temp PLA, and so on. The best way to find out is to try, right? If you do try a different plastic, please let me know how it goes.

How long does a Sharpie last?

A long time. Beebe estimated it would last for a whole spool, and I think that is realistic. I have been swapping between different Sharpies for the last few weeks to print different colours, and I’ve been leaving them connected to my printer and uncapped for several days between printing jobs. All of the Sharpies are still fine.

Do the Sharpies foul or clog the nozzle?

No, my 0.4 mm nozzle is fine. Sharpies just leave some wet ink that can be either cold-pulled out, or purged by extruding a new colour. The exception to this is metallic Sharpie which leaves behind all of the sparkly metallic particles. These don’t clog the nozzle, but they resist being extruded and need to be cold-pulled out (see image below).

How quickly can colours be swapped?

The basic steps involved are:

1. Remove Sharpie and cut off coloured tail from previous colour.
2. Form a point and guide fresh filament through the Sharpie.
3. Insert into machine and extrude 20 cm until colour is steady.

If the machine is already hot, all of this can be done within 1 minute.

Can the colours get any stronger?

It can get darker, but the quality of the colour becomes worse. I noticed that the way the filament is pulled through the Sharpie affects the colouration: The start-stop motion of an extruder, which pulls only a small amount of filament through at a time, leaves a thin coat of colour on filament and a gentle pastel colour on the printed item. In comparison, pulling a bunch of filament through the Sharpie by hand makes a really heavy coating on the filament, but this dark colouring doesn’t come through in a consistent way (see image below).

Can I mix colours?

Not with the method shown here. I once tried inserting some yellow-coloured filament into a blue Sharpie. The filament at the top became green, but by the time it exited the Sharpie the solvents and ink sponge had stripped the old colour off and left only the blue behind. The final print colour was an unmodified blue.

You might, however, be able to get away with something like this which uses two Sharpies to colour different sides of the filament as it passes through, so that neither Sharpie can rub off the other’s colour. However, you would be relying on the colour to mix evenly inside your nozzle.