How to Dye Models from Shapeways, Part 1

Shapeways offers a number of different colours for their laser-sintered nylon (“strong and flexible”) models.  However, I sometimes want a model in a solid colour that they don’t offer.  I first played around with dying my own models a few years ago, and recently visited it again today.  I am going to document this method over the course of several posts simply because this round of dying did not turn out the way I expected.  I will elaborate further down.

The models I decided to colour are as follows:

The dye is from Dharma Trading Company:

Dharma provides instructions for use of these dyes, however, those instructions are for clothing, so I had to tweak them.  I have done this once before with #446 “silver gray,” and it worked perfectly.

Step 1: weigh your models

For ease of calculation, I rounded this up to 85 grams.

Step 2: measure powdered dye

I use 2% of the weight of material being dyed, which comes out to 1.7 grams.  In order to make this easier to mix in the pot, I then immediately dumped this into a small beaker containing 30mL of water, and stirred with a glass rod.

Step 3: measure vinegar

I use 12.5% (1/8) volume/weight of white vinegar per weight of material being dyed, or 1mL for every 8 grams.  This came out to be just over 10mL.  I suggest keeping a small reserve of vinegar on hand in the event you need to add more to the pot later.  Bear in mind that this is highly un-scientific, and the amount of vinegar you use will be dependent on how dark you want the colour to be.

Step 4: put models into a pot and cover them with water

Ideally, you should use a laboratory hot plate with a magnetic stir bar to keep the mixture circulating.  I have one, but it doesn’t work anymore, so both times that I’ve dyed models, I’ve used a regular stove-top, stainless steel sauce-pan, and thermometer.  You want enough water so that each model may be completely submerged, with enough extra so that it can evaporate and not expose them.  Note that, although laser-sintered nylon is porous, it will never sink to the bottom.

Step 5: bring the water up to 90 degrees Centigrade (195 Farenheit, or 363 Kelvins), and keep it as close as possible to that for the duration of the dye-job.  This is where the laboratory hot plate comes in handy, and I will probably invest in a new one for this exact purpose.

Step 6: add the liquid dye concentrate that you just mixed up.  Pour it into the water, and try to avoid pouring it directly onto any of the models.

Step 7: add the vinegar, again try to avoid pouring it directly onto any of the models.

Step 8: stir, invert models regularly, and maintain temperature.  Pull one of them out of the pot every now and then to check the colour progress.  Depending on what colour you’re looking for, this may take anywhere from 15 minutes to an hour.

Step 9: remove pot from heat, dump dye down the drain (this is perfectly safe), and rinse off models.

Now then, assuming you’re using a colour like “silver gray,” you’re probably good and don’t need to keep reading.  If, however, you’re using “moss green,” as I was this time, there is something you need to know.  It turns laser-sintered nylon blue, not green.  Above is a rather blurry picture of the T-10 main gun, which I pulled out after 17 minutes.  Given the print orientation of the part, it absorbed the dye very quickly.  The white patch is simply where I had glued it.  You will notice, regardless of what colour you use, that the colour will be much more prominent on the print lines, and less so on the faces that are parallel with the layers.

There is nothing wrong with this dye, it simply doesn’t colour the plastic the way I expected.  Everything else turns green, just not the models.  In the future, I will put these same models back into the pot with a yellow colour, and see if I can fix them.  In the mean time, I will try different greens from Dharma until I find one that I like.  Here are the results:

It’s a very pretty colour, just not the one I was looking for.  In later posts, I will document an experiment to fix these models, as well as let you know what colours from Dharma produce what results.