We've been unhappy with the general evenness & surface quality of the black SF material. 1/2 of our customers want black products to match their phones, so it's become a high priority to try to find a better black material.
We also REALLY like the surface quality of the PWSF material, and so do our customers. Its smoother & has less of a gritty feel.

So we've started running some tests of dyes.
We first tried Rit dye Black, using a formula of 8 cups water, an 8 oz liquid bottle, and 8 teaspoons of vinegar. We heated to 60C (that was the recommended temp) and immersed parts for up to 6 hours. The WSF got quite dark, but always had a bluish cast - not a true black. PWSF was much worse - a nice navy blue but NOT black.

Today we tried iDye Poly from Jacquard Products in Healsburg, CA, bought at a local Joanne's Fabrics. About $4 per packet, which includes the powder dye & the brightener. Again the formula was poured into 8 cups water - just a bit more than needed to cover the parts

This we ran at 80C for 1 hour on a WSF, and 40m on 2 PWSF parts. The photo of the result is enclosed - the PWSF parts on the left, the WSF on the right.
You may need to adjust the brightness to see the engraved Nautlius logo. But we were reasonably pleased with these initial results.

One issue - for some reason the PWSF parts had a buildup of dye on the surface after removal. Hot water and detergent cleaned it off nicely, no change to the color. I spoke with Monty Witherby (sp?) at the company who recommended running at 100C (keep it at boiling) but we kept it below 80C as the data sheets recommended 80C max temps, even though the softening point of the nylon is much higher.

Note the WSF & pWSF are just slightly less dense than water, so parts float (barely). We stirred the baths every 5-10m, & had the logo faced down. Yet all sides were covered quite evenly.

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I also did my own tests. Minimum boil time was 1 hour. I always boiled. It makes the plastic softer though, but I think shapeways, sculpteo, and materialise all boil too.

Acid dye needs PH 5.0 while Lanaset Dye needs PH 4.5. The Acid and Lanaset turned out the best, but they still were not exactly black. I used 40mL/1L of vinegar (5%) for Lanaset, and 15mL/1L for the Acid. I tried the Acid dye again with 40mL/1L but this turned out red.

I made a mistake in the iDye Poly + clearcoat label. This was 2 hours, not 1 hour, and it was much darker than the 1 hour, but it uneven with patches of red. The 1 hour was clearly reddish. The Lanaset is slightly blue. The Acid was more neutral, but a bit gray.

I may just change my desire for black and go with gray or some other color that doesn't give customers an expectation.

adding a clear coat really darkens the color.

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[Updated on: Tue, 18 December 2012 20:07 UTC]

So I ran another batch of dye, this time fresh made, kept temps 60-70c, ran for 40m. I used one pwsf case & the two cases that came out reddish before] to try to get them blacker.
The virgin case came out nicely black as in the first test. The other two (right side pix) got a bit darker, but still reddish & more glossy.
So fresh dye is key, temps also.

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Quote:

EOS has a black material similar to the white. I'm surprised Shapeways Doesn't use it.

We have seen the EOS black and it isn't nearly dark enough. Rest assured that Shapeways is working hard on this problem.

[Updated on: Fri, 11 January 2013 17:11 UTC] by Moderator

I just talked with Monty and got a pix of the results from his dye tests. Couple of interesting points:
- acid dye did not work at all - he said he had never seen a material which repelled the dye as thoroughly
- he went with a much stronger concentration of iPoly dye than we used, and got a jet black result (see pix) Black is the most difficult "color" to achieve for ANY dying process.

So what he recommended was using 8-10% (he used 8%) by weight of iPoly dye and carrier, and running at a rolling boil (100C) for 30m. Running at a boil would prevent the gunk buildup issue we saw, and should allow for simple easy cleanup of the part in post dye rinsing. Use equal parts dye and carrier (or intensifier) in the mix.
By my math, this is 10X the concentration we were using! We used 8 cups of water, which is about 2 kilos. One packet is 14ml of dye, 14g carrier or about 0.7%.
He recommended we buy direct from them, and talk to Victoria Garcia to order the dye and carrier in bulk - buying the packets will be much more expensive otherwise.
Maybe a lower concentration would work, but we'll run some tests using this formula and see how well it works on our regular parts.
I would imagine with this strong concentration, one could dye quite a few parts before needing to change the bath.

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[Updated on: Wed, 20 February 2013 18:01 UTC]