Clear V4 Resin Printing Yellow

Hi Everyone,

I am printing with the Clear V4 Resin for the first time. The second the print was out of the Form 2 I noticed that the model had a yellowish tint to it. I also noticed the supports were completely clear but the actual model I wanted to print was a cigarette stain yellow. I used a brand new tray, and just ordered the resin last week. My printer is not located in the sun or near any significant sources of UV light. As a matter of fact, most of the printing occurred at night with hardly any light. I’ve included pictures of pre-washing, post washing and post curing (10 and 15 min increments) . This model will be sanded down by a professional in the near future, but I have to make sure that it looks clear and translucent, not stained yellow. Any solutions will be greatly appreciated, thanks again.


That’s probably normal, but it’d likely look less yellow after sanding and polishing

Those are the results I get with expired clear resin. Did you check your resin batch date?


I just checked the resin batch number, it was dated for April 4th 2019. I literally JUST ordered this resin last week. Why in the world they would send you expired resin is beyond me, Thank you for your response it is greatly appreciated!

I suppose you checked the label on the bottom of the cartridge? The resin is not expired. It is manufactured at April 4th.

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I think the problem may be the print part is too thick, when the Clear Resin get curing too long it would get stained yellow look .

As you not get post curing too long , but the thick Resin itself will get more heat than thin part when it get curing by laser . This can make it get stained yellow look .

So is there actually anyway to print something as thick as this model without it being tinted yellow? The thickness is .5 inches. I’ve seen other clear prints that were just as thick if not thicker and still maintain optical quality. I understand the intensity of the laser, but is there any sort of adjustments of settings that I can try? I printed another model the exact same size (just in case the first one was a one off print) and it does the exact same thing. Also I only cured the first print in increments of 5 minutes at 60C and there was no improvement.

The reality is that all prints in clear V4 have a degree of yellow tint to them. That gets worse after post cure. (Further exposure to UV and completion of the cure of the material into polymers) Age of the print also causes further yellowing after a long period of time.

The yellow becomes more visually apparent as sections become thicker.

Unless Formlabs change the formulation of the resin that problem is not going to go away, and the only solution presently available with the Form2 is to look at third party resins which are formulated to minimise yellowing. Unfortunately its the nature of the beast and is a widespread issue for resin formulators. The true quest is to minimise the degree of yellowing to acceptable levels through clever chemistry (its almost impossible to totally eliminate the yellowing effect due to the chemistry available today, and the wavelength (405nm) available for the cure).

There are third party resins available (that have NOT been formulated by Formlabs) that are significantly better with regards the degree of yellowing.

A true non yellowing clear resin at 405nm is the Holy grail of resin formulators!!

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I still have a couple of prints I did back in 2016 with Clear v2, and they haven’t yellowed.

I’m sure that overcuring during print might contribute to the yellowing, Age of resin certainly has a lot to do with it, but then again, I haven’t used Clear v4 so I can’t speak to its properties.

But my point is that FormLabs certainly knows how to make a clear resin that stays clear, they’ve done it before. It’s not some sort of “unobtanium”.

Was the 2016 print post cured?. If not then it was not fully cured. Was it out of daylight, if not (and was not post cured) then it was never fully cured. Pop it out in the sun for a couple of days and see if it goes yellow. If not, then clear V2 was truly a non yellowing clear resin

It only takes a small change in the resin chemicals or chemical suppliers to go back to yellowing. Yellowing of UV cured materials is a big issue, and one that has been a problem for UV formulators since the 80’s (Look at 2d printing of coatings). If you look at the base chemicals some are even described as “low yellowing” in the manufacturers technical data sheets

I also have some 2016 with Clear v2 print, all without post cured , just cured by indoor daylight .

One without any protections becomes a bit yellow.

Other got clear coating spray print, don’t have too much yellowish look over the time up too now .

One of them in this video :

I have some 3 parties Clear resin print on LCD printer , thicker part become more yellowish right after the post cured ( I think the heat and UV ), but it will reduce the yellowish after 2 weeks in indoor daylight ( without any protections).

So there so many variables can cost it more yellowish or not .

You best bet should be made a silicon moulding out of the print, and use longer curing time moulding Clear resin to made it . ( longer curing time one in most cases are “low yellowing” )
I do have some moulding casting clear resin don’t yellowish after more than 30 years .

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