It took me 7 ASA brands to find one that I found to be a true red both before and after acetone smoothing. So I thought I’d give a shout-out to iSANGHU for overcoming the inherent paleness of ASA and making it a vibrant red!
Honorable mention to Polymaker Red ASA, which is quite red off the build plate, but it shifts orange during acetone smoothing. The other 5 were just not very red at any stage.
Apparently I am a terrible photographer, because I really tried to capture these colors in a picture, and this was the best I could do. As you can see, most of them have obvious orange or pink leanings, and the one at the top is actually much more brown than it looks in this picture. But the iSANGHU is just red. At least to my eye!
(These were all printed with similar settings and acetone-smoothed by the same procedure.)
Also interesting: These are 7 unique shades, which is great for us because it means more choice. When I started this, I was a litlte worried that all of the red ASA in the world would just be coming from one factory, but that is clearly not true!
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Keep in mind that acetone isn’t the only solvent possible here and that other solvents might have a very different effect on the stuff that makes the colours.
That printed parts tend to change colour during chemical treatments isn’t news.
This was already an issue for model makers and car lovers long before we had 3D printers…
A little drop missed, the brush sprinkling fine solvent drops while wiping the excess off or just the brush left sitting close to a part,…
When all this became the news in the 3dD printing world we saw a lot information but no answers.
So what is causing coloured plastics to change colour levels or sometimes even shades after contact with solvents?
The dye in certain plastics reacts with solvents but in filaments we usually only find pigments and additives with colours, so what gives?
Both the filament and the pigments are carefully tuned to become a perfect match.
If you ever colourer resin or concrete using pigments you know that a little can go a very long way here.
Our problem starts not so much with pigments being affected by our solvents, they are surprisingly resilient in most case.
No it is far simpler than that, it is light.
The plastic affect how light is reflected and passes through, hence black filament being black and usually not see through either…
We need a ton of pigment to get a decent black, same for a solid red, green or blue.
For many colours though we can combine pigments with additives of suitable colour, which brings the nightmare for those relying on solvent treatments.
The solvent, by design, dissolves first was it easiest to attack.
Then the more stubborn things get affected.
Once done the same happens in reverse when the solvent evaporates, just with a few little twists…
Spray paint is like plastic with pigments and an awful lot solvents.
Unlike spray paint our filament was never designed to work WITH solvents, only to melt together to result in a still usable plastic.
So when it all melts and goes smooth those pigments get freed from the plastic and the plastic composition also gets separated to some good degree.
Pigments can appear in different shades of the same colour and in vibrancy just based on things like particle size and how rough or smooth their surface is.
If those fine particles end up ‘sinking’ out of the surface their overall density changes, which affects how they reflect light.
Being coated with more or less translucent compositions within the filament affects the reflectivity of the pigment, how it scatters the light spectrum.
There is actually far more going on during and after vapour treatment than what meets the eye…
Another interesting test you could add now after all this hard work and with so many blends of ASA around:
Print strips or such to see how the acetone treatment affects the physical properties.
Like rather thing strips where the solvent treatment is likely to make it all the way through and a bit thicker ones where the treatment won’t affect the inside.
You might be surprised by how many good and how many not so good things you discover.
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