What will happen when we put photopolymer resin to daylight…?

In previous article I described my attempt to break my The Form 2 3D printer. Fortunately for me it ended in failure, however, thanks to this I managed to gain new experience, which I did not fail to share with you. At the same time, it inspired me to conduct some experiment, the effect of which was to get to know one of the most pressing questions of photopolymer 3D printer users – what will happen if the resin is exposed to the light of day? Will it actually harden? How fast? Is it worth paying attention to it at all?

Before we go any further, I would like you to treat my “experiment” with an appropriate distance and a pinch of salt… The things described below are obvious, but they nevertheless prove them beyond any doubt. In the end, we live in a time when more and more people are seriously wondering if the Earth is flat…?

As the name suggests, light-curing resins cure (photopolymerize) under the influence of light. They were developed for the needs of industry by the DuPont concern in the 1950s and became the first material from which spatial objects were created (in 1984, Charles Hull – the creator of stereolithography, the first additive method in the world). Light-cured resins are one of the most frequently used consumables in 3D printing – they are used by 3D printers working in such technologies as: SLA, DLP, PolyJet, MJP, CLIP, 3SP, MovinLight and others.

Depending on the method, the resins are cured by various methods – a laser beam, light emitted by a DLP projector, LCD screen, or UV lamps. Of course, the resins also cure under the influence of natural daylight. Due to the fact that in SLA / DLP machines, the resin is in open containers, to prevent them from accidental exposure, the whole printing system is closed behind a shade made of plexiglass in orange, red, yellow or green.

Ok, so many theories – what will happen when we still put such a resin in the light of day? In the experiment, I used the last of the Dental Model resin, which became the source of my problem, which I mentioned in the introduction.

I put the resin in the container on the terrace in a sunlit (though cool) day. Photopolymerization took place in less than 10 minutes…

Only the upper, about 2-millimeter layer of resin has been hardened – the resin under it remained intact.

After removing the hardened layer, I put it back outside, this time on a very cloudy, quite sunless day. As before, photopolymerization of the upper resin layer took place in just 7-8 minutes.

Therefore proved! Light-cured resin must be protected from daylight, because even a small, minute exposure causes its complete and irreversible bonding. I did it so that you would not have to try.