I have done some research and could not find any relating threads. I am printing with near UV and diacrylate polymers. My tests with pigments and dyes have not been fruitful so far as my material has a very high water content (~90%) and color just diffuses over time. Even if my parts are beautifully stained right after the printing, the defined color distributes throughout the object over time. So I am looking for some kind of water soluble dye/pigment that stays in place after polymerization, maybe even by covalent bonding. Any ideas are highly appreciated. https://reprap.org/forum/read.php?184,642876,642876#msg-642876 Tue, 19 May 2026 02:48:23 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?184,642876,763516#msg-763516 https://reprap.org/forum/read.php?184,642876,763516#msg-763516 zhongwangli Polymer Working Group Fri, 21 Apr 2017 04:14:22 -0400 https://reprap.org/forum/read.php?184,642876,643328#msg-643328 https://reprap.org/forum/read.php?184,642876,643328#msg-643328
I tested acrylic paint yesterday and that seems to do the job.

I will try to raise the thixotropy if the object becomes uniformly colored over time.

Thank you very much for your help, new ideas for the next tests.]]> der_Bam Polymer Working Group Wed, 23 Mar 2016 06:37:43 -0400 https://reprap.org/forum/read.php?184,642876,643105#msg-643105 https://reprap.org/forum/read.php?184,642876,643105#msg-643105
I think pigments might be more promising; you maybe able add an additive that would increase the thixotropy of the resulting gel and slow down the migration.

The next thing I might try would be to add cabosil (fumed silica) to the resin, starting with about 1%, and see if that slows the rate of pigment migration.

Is your printer very sensitive to the viscosity of the resin you print with? If it's not very viscosity sensitive, you can keep upping the amount of cabosil to see if it improves stability, and can go to quite high concentrations.]]> jkao Polymer Working Group Tue, 22 Mar 2016 15:20:34 -0400 https://reprap.org/forum/read.php?184,642876,643094#msg-643094 https://reprap.org/forum/read.php?184,642876,643094#msg-643094 der_Bam Polymer Working Group Tue, 22 Mar 2016 15:04:27 -0400 https://reprap.org/forum/read.php?184,642876,643085#msg-643085 https://reprap.org/forum/read.php?184,642876,643085#msg-643085
Dyes are dissolved into solution with the material, so even if they migrate over time, any movement should not be visible. The drawback of dyes is that even the most durable dyes (e.g. metal complex dyes) will fade over time with exposure to UV. However, unless your printed objects are outdoors in the sun for long periods of time, or perhaps exposed to repeated UV sterilization, objects indoors would not be exposed to enough UV for this to happen.

Pigments, on the other hand, are suspensions. If the cured material isn't completely solid but is actually a gel, it is possible for pigment to settle over time according to Stokes' Law. But given the viscosity of the typical gel, this would occur very slowly if you use a fine pigment in the 1 micron particle size range, and would tend to settle towards the pull of gravity.

I notice also that you said the problem was "color distributes throughout the object over time". Does this mean that you are somehow producing a multi-color print with two differently colored resins and you're seeing that the colors diffuse into each other, like perhaps via osmosis?]]> jkao Polymer Working Group Tue, 22 Mar 2016 14:46:39 -0400 https://reprap.org/forum/read.php?184,642876,643068#msg-643068 https://reprap.org/forum/read.php?184,642876,643068#msg-643068 der_Bam Polymer Working Group Tue, 22 Mar 2016 14:05:28 -0400 https://reprap.org/forum/read.php?184,642876,643030#msg-643030 https://reprap.org/forum/read.php?184,642876,643030#msg-643030
Or are you saying that in your application, you are staining your object by immersing it in dye after it is printed rather than adding dye to the liquid resin?]]> jkao Polymer Working Group Tue, 22 Mar 2016 13:09:05 -0400 https://reprap.org/forum/read.php?184,642876,642876#msg-642876 https://reprap.org/forum/read.php?184,642876,642876#msg-642876
I am printing with near UV and diacrylate polymers. My tests with pigments and dyes have not been fruitful so far as my material has a very high water content (~90%) and color just diffuses over time. Even if my parts are beautifully stained right after the printing, the defined color distributes throughout the object over time.

So I am looking for some kind of water soluble dye/pigment that stays in place after polymerization, maybe even by covalent bonding. Any ideas are highly appreciated.]]> der_Bam Polymer Working Group Tue, 22 Mar 2016 07:07:30 -0400