Use RIT fabric dyes to add any color to your sintered nylon 3D printed parts.
Adding color to 3D printed pieces can help us distinguish parts from one another, emphasize details, enhance photographability, and, of course, improve aesthetics! With all these valuable properties, it is a shame that selecting colorful parts from 3D print manufacturers is so expensive.
Fortunately, there is a cheap, quick, and convenient solution: dye the parts yourself!
Many companies actually use dyes to color sintered nylon pieces during post-processing, rather than beginning with colored filament. This means that dyeing the parts at home will produce a similar outcome in terms of vibrancy, uniformity, and durability.
The only major difference is the price tag! The parts pictured came from Shapeways, where each dye bath would cost $6 per part. Besides black, I was able to reproduce all of the colors that Shapeways offers using only 3 very inexpensive dye colors! I was very thorough in coming up with dye recipes to find the perfect way to make saturated colors that covered the parts evenly, and did not fade away over time. This involved a ton of supplies and hours experimenting.
Some parameters I tested were heating time, soaking time, dye volume, dye bath additives (dish soap and vinegar), fixative presence, stirring frequency, and of course, color ratios.
All Purpose Dyes
I began using RIT All Purpose dyes. Although the formula is designed for natural fibers such as wool and cotton, one of the recommended materials is, in fact, nylon. Nylon is a popular fabric for stockings and outerwear, and even though it is a synthetic fabric, it absorbs color very well. Unfortunately, when I tried out the All Purpose dyes on the 3D prints, the colors turned out pale and patchy. Even the samples that seemed to work alright, such as the black dye, faded to a grayish blue approximately 4 weeks after dyeing.
I experimented with many different heating times, stirring frequencies, dye concentration, added dish soap, and other parameters, but nothing really improved the appearances to colors that would rival Shapeways' ones.
The next test was to try Synthetic dyes. Since vinegar is a recommended additive to the dye solution when dyeing nylon fabric, I decided to test it on the printed parts as well. I also wanted to find out whether or not RIT's Color Stay Dye Fixative made any difference in the color saturation or durability.
From left to right: Vinegar+dye, dye only, dye+fixative
The vinegar solution produced a slightly lighter color, and actually caused an uneven color distribution throughout the part. Non-uniform color saturation was not desirable for my 3D printed protein models project, so I did no further testing with that solution. Using simply water and dye had fairly good results, but the color was a bit pale and actually faded over the course of several weeks. The final trial involved a solution with just water, and was then transferred into a separate container with the fixative at the very end. I used this final method to dye the rest of the parts.
As you can see, all the parts that were supposed to have blue hues failed. The Kentucky Sky dye did not work on these parts. I decided that since the Indigo All Purpose Dye worked alright in the past, I would try dyeing over the failed colors here, and locking the dye in with fixative. This was fairly successful for this round of dyed parts (the connector pieces with circles on the ends), and when I used the recipes to dye clean, white prints later (DNA bases), they turned out beautifully!
After many trials, the best colors ended up coming from two dyes from the RIT DyeMore for Synthetics collection (Super Pink and Daffodil Yellow), and one from the RIT All Purpose Dye line (Indigo). The other RIT product I used was the ColorStay Dye Fixative. This chart depicts what quantity of each I used to reach the desired output color (shown along the top row). All of these measurements are to be added to 1.5 cups of water, as described in the tutorial below.
Other supplies I used that you may have on hand include glass measuring cups (I used Pyrex), tongs, measuring spoons, plastic wrap to protect household surfaces, and lots of paper towels. It's important to note that these tools cannot be used for food preparation after they come into contact with the dye. You will also need tap water and an appliance to heat up the water (I used a microwave). Here are the steps to dyeing parts. If you have multiple parts that need to be the same color, dye all of them at once.
Pour 1.5 cups of water into a medium sized glass measuring cup
Mix dye into water
Microwave on high for 3 minutes
Place part into hot solution with tongs
Lock the tongs to keep the part submerged
Soak for 15 minutes
In the meantime, pour 1/2 cup of water into a small glass measuring cup
Add 1 tablespoon of dye fixative
Microwave for 1 minute
Soak part in fixative solution for 15 minutes
Rinse the part with cold water
Pat dry with a paper towel
Leave to air-dry overnight
I stored all these dye mixtures in airtight plastic tubs to reuse again and again. I still have not experienced color fading despite dyeing many parts in the same solution, but once you've used the dyes enough, you will have to add more dye in, one teaspoon at a time, until you reach the desired color.