Overburning for highlighting areas of interest (two color tone sla printing)

Hello everyone,

With many sla machines it is possible to highlight areas by having the laser cure certain parts longer or more often than normal.

Does anyone know if that might be possible with the form2, as well?

Thanks a lot!


You can’t change the cure time, if you want an effect like that it would be better to model your mesh with that type of marking which will print more successfully.

In theory it should not be too hard to implement it. I would bet most customers would love to essentially print in two colours!

If everyone who would benefit from it comment here we might get formlabs to do it. Unless the fuse1 printer that is coming out will print in two colours and it would compete with that.

I would really appreciate people wanting that feature to comment!

Have a nice day !

Formlabs just told me that it is something they could choose to implement. That would be really exciting!

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Increasing exposure would dilate and stiffen the part (until it is post-cured, at which point it would basically all be fully cured). You wouldn’t get a difference in color.

If you intersect models, they both get drawn, double-exposing their overlap. It won’t do anything exciting, I’m afraid.

Sounds logical what you are saying. Thanks for the answer ! But how is it that the expensive machines can do it then?

Best regards,


Can you provide a product name or a photo or a link to what you are talking about?

Hi, sure. Here is an example. I specifically asked how it was made. It was an SLA Printer.

Best regards.

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I wonder if they’d be able to make other colors than just clear and orange-ish.

My guess is they are using a resin that is very bad at resisting UV light and gets a strong yellow tint when it’s exposed to the laser for longer than the nominal cure time.

There is also the possibility of using irreversible photochromic pigments which basically are clear when not exposed to UV light but then change color as they absorb UV and don’t revert back to a clear color afterwards. Still, they would be only clear and another color, not really two different color AFAIK.

Also, this would mean over curing some parts and not others, wouldn’t that cause geometric irregularities in the print, just like printing a part directly on the base does ?

Models like these also exist with clear and pink instead of clear and orange.
I don’t really know how it’s done. Maybe no post curing is needed after printing. The techs, engineers and material scientists from formlabs probably know it. Alternatively it might be possible to find a patent in the Google patent data base.

If the resin changes color as a function of how cured it is, and you post cure so all the resin is fully cured, the result would have to be a print that is all the same color…

that is true. but maybe a kind of overcuring is possible which would lead to a color different to fully cured areas/parts

Wonder if that was done with a top down dlp printer where they print one color one set of resin then change resins and print the other resin like an over mold?

I am not sure how that would work. could you elaborate on that, please ?

best regards,


By the looks of that particular print I am guessing it was done on a polyjet that has multiple material heads. If it was done on an sla of sorts the only way to get different materials is to literally change the resin. This is no way of having 2 different resins in the same tank at the same time.
The only way I could think of doing something like that would be with a top down style machine such as some of the DLP printers are done and you would have to print one color. Leave the part on the build platform then change resins and print again. This wouldn’t be possible on a machine that print from the bottom like the Formabs because you wouldn’t be able to build layers with a structure in the way.

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Yeah, there’s no way an SLA printer can do that type of thing.

Both the red and the yellowish tan colors are made by hatching (overcuring) certain resins which change color with exposure to UV. The tan tint is made with Somos Watershed and the red is Accura YC9300. The software for certain SLA machines allows to submit overlapping STLs with different cure parameters. The models need to be protected with a UV absorbent clearcoat, but will still gradually discolor (rapidly in direct sunlight). I have asked FormLabs for that for years (since beta testing Form 1). We use it all the time in biomedical models for marking teeth, nerves, tumors, as well as marking patient names. You can see several examples at www.biomodel.com


thanks so much for your answer! I knew it was SLA printed. The faster degradation in sunlight is a downside, ofcourse, but still, thats just great to not use a jetter for that.
Seems to be not that easy to implement. I am sure so many formlabs users would love to print in two colors.

thanks for the URL, as well. I will check it out.

best regards,


I just realized the full color anatomical model of a human head i saw at Rapid+TCT in Pittsburgh is your work. Very impressive! Great work! I bet the segmentation was fun :wink:

Thank you… Yes, it was a challenging combination of segmentation and digital sculpting.