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Recycling IPA Without Distillation (Ongoing Project)

Good afternoon,

I am employed at a company where we print non-stop, every day with our Form 3 and end up with a ton of used IPA. Sadly, as I am sure mot of you are aware, recycling IPA and the resin is a pain (at least in our area). In an attempt to reuse IPA without the concern of distillation, we are attempting to use UV lights and time to separate the IPA and resin.

I wanted to share our experiment and share our results and maybe get some suggestions.



  • Cleaned fish tank (free but plenty of cheap/free options on Craigslist)
  • UV Led lights (Used these as these perform identically to the Form Cure)
  • Cardboard
  • Some old wood
  • 18AWG wire

I arranged the UV LEDs to the top and bottom of the tank to make sure the light hardens the resin as best as possible. NOTE: The LEDs are NOT WATERPROOF. I only have these on during working hours and when I am present in case of fire. I put the bottom ones on wood with smaller cuts as risers so the tank isn’t laying on top of them.

I then used my remedial arts and craft skills to create a box lined with left over recycled material from my bosses art stash. This is to allow the light to hit it at as many angles as possible. I added a plank of wood to life the cardboard up and above the tank to allow for “easy” access (I am sure there was a smarter way to do this, but I never claimed to be smrt [I mean smart]).

07/29/21: So far, the resin is a thick gel and has separated pretty well. The issue is a cloudy IPA. What I am thinking is missing is heat. I do not have the ability to put this in the sun at all. I am thinking a heat lamp, but not sure if it will work. Hoping for a response from the community on their thoughts.

Thanks and I hope this helps and please do not hesitate to offer your own knowledge.

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UV lighting might work better than heat lamps, which have wavelengths in the IR region, I think. If you use UV lamps take care to protect skin from exposure - I once hot a nasty burn from a UV lamp after a half hour or so of exposure.

If you let the IPA sit without agitating it for about 48 hours, almost all of the resin should precipitate out leaving a sludge (you can then cure) at the bottom of the tank and crystal clear IPA above that point.

I submerge a paper towel covering the bottom of the tank, come back a couple of days later, and slowly draw it out. I’d guess I’m removing 90% of the particulate.

You might also get better results if you increase your UV LED strip count by 2 or 3x.

Tried many similar combinations of your idea and nothing worked. The IPA either didn’t fully evaporate in a timely manner or the resin’s residues were a pain to handle.

I ended up with this solution:

Not only it takes the resin out of the IPA but it also recycles it so that it can be reused over and over. 2 hours for a Form Wash basket full of dirty IPA (7 to 8 liters) gets me around 6 liters back.

Wow quick replies!

Thanks! I will look into that.

It actually took much longer for us oddly enough. I think its due to the lack of actual sunlight we are able to get. The IPA looks clear, but is still cloudy. I had a similar idea with the paper towel! We plan o n syphoning the alcohol out, leaving the sludge to be plopped out. We have two strips at the bottom and the two at the top, but you think more would allow the resin to solidify quicker?

Maybe I am a fool (more than likely) but what am I looking for in that link you provided? To be clear, we use the Form 3, not 3L if that matters to your provided link.

Thanks for the input, all!

Sorry, pasted a wrong link for whatever reason. Already edited it but here it is: Form 3L Issues

Btw, Randy’s suggestion works great as a regular cleanup solution, had used it in the past as per his suggestion.

I see thank you! We are def going to do our best to use as little energy as possible as well as keeping it DIY, but even the most conscious men have their limits :stuck_out_tongue:

I will show this to the team! Thanks.

Those strips, I would wager, are at best a few Watts in sum total of all the LEDs. The energy required to cure the resin has, I think, an exponential curve. Below some threshold there isn’t enough energy to kick the polymerization process off. And the LEDs on the top are much further away than the ones on the bottom. Remember, light energy falls off with the square of distance. If the top LEDs are 8x further away from the IPA than the bottom LEDs, they’re delivering 1/64th the energy.

Also, those inexpensive “UV” LED strips may not be quite the right frequency. I bought LEDs for my UV curing station, and had to do a fair amount of searching to find some that were guaranteed to be no higher than 405nm, and I think the FormLabs lasers are closer to 385nm.

Thank you for your insight.

I was basing the amount of nm on what FormLabs says their curing machine does, 405nm. These LEDs claim 405-395nm. They are 24 watts. I know FormLab’s product uses LEDs too, but what would be the wattage I should use? This is all new to me so I apologize for lack of knowledge.

I have enough extra to wrap a single line of them around the tank. I will dig out a wall power adapter and solder it on later.

There is no amount of wattage that is too high short of boiling the IPA.

My UV curing “jar” has a single strip of LEDs, but they have tighter spacing (there are more LEDs per strip) and the strip wraps around the jar 5 times, so I’m putting about the same amount of light as you, maybe, but in a space that’s a fraction of the size of your fish tank.

Are these 12V or 5V?

Experimenting with organic chemistry is fun of course but if you are generating that much dirty IPA as part of normal business operations, you may wish to consider a commercial grade solvent recycler.

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Agreed. We will be shifting to another company to mass produce our product, but are in a weird spot between that happening and a massive order, so we don’t plan on doing as much printing in the future.

@Eks What exact model is that alcohol distiller? How’s it been working out, any gotchas so far? What kind of resins was the alcohol saturated with beforehand? How bad is cleanup after use?

How do you think it would compare to this one Formlabs posted a while back:

Or this guy here (posted by @qupada) with a disposable bag for the residue:

That’s the IST C1 model. Basically the C1 holds 10 litter and the C2 holds 15.

It’s been working out great, one of those rare “As advertised” things.

I use all of FormLabs materials so it’s usually a mix of many resins. Basically it doesn’t matter because the alcohol evaporates and whatever doesn’t evaporate stays there. The evaporated alcohol then condensates to a container to be reused. I haven’t done any chemical test since that’s way out of my league but I’ve reused the alcohol dozens of times and still smells the same and cleans the parts as well as fresh one (to the best of what I can notice, at least). I do add almost one litter to fill up the rest of Form Wash’s bucket but that’s it. Saving 6 out of 7 litters is good enough for me and adding the waste management (which was my main priority) to the mix is just perfect.

The cleanup is 99% easy: A bag is added inside the container and then the dirty IPA inside the bag. Once all the magic happens all that’s left is some residue (the resin) at the bottom of the bag which just needs to be closed and tossed. The 1% is some liquid residue that somehow and some times gets outside the bag but that’s cleanable with paper towels and a bit of IPA sprayed into it. I do as they recommended which is to wait a few hours (like “next day”) to open the container and take the bag out due to the smell as it gets intense when still hot. The smell is NOT noticeable at all while the container is closed.

I was really amazed how easy that is and it doesn’t take a lot of space (which wasn’t something I could afford to waste). The only downside is that it gets a bit hot around the machine for the ~2 hours it takes to recycle but that’s what it is since it’s cooking things at high temperatures.

Before this I waited from 30 to sometimes 70(!) washes before replacing the IPA and now I do it between 10 to 20 as soon as I don’t like its color. It was not because I was lazy or something but because I was having a hard time disposing of the IPA and resin combined and that was driving me crazy because around here there’s zero places where we can do that.

Hi all, here’s what I do:

  1. stand the printed parts on kitchen paper to allow to drip excess resin off
  2. wash in TPM
  3. rinse in warm soapy water, let it dry
  4. wash in IPA, let it dry
    This process has the advantages that the TPM absorbs lots of resin without much of a negative effect, while the IPA remains clean for many washes - 50 so far and it’s still so clear you can see the agitator at the bottom. Disadvantage is that you need at least 2 wash machines.
    The other posters are right though, sunlight hardening the IPA does work, and you can siphon the clear liquid off the top after letting it settle.

Good morning!


Taking the advice given, I have moved all LEDS to the bottom on a tray of sorts. I used the loose strip I had left on the side to see if that would help at all. I am still considering a higher wattage LED but this being a side project, we aren’t super keen to keep throwing money at it. if the cloudiness subsides by Monday, I think we will try to extract the IPA and test its effectiveness.

This community has been super knowledgeable, kind, and helpful so far and we are super impressed and thankful for all of your time!

Wow, this is a super interesting solution @partyshark! Please let us know how your effectiveness testing goes!

WIll do!

I did try to extract the IPA and clear the resin slop at the bottom, but the liquid was still cloudy (without distillation I don’t think it’ll be perfect) and the removal of resin was like herding cats. I will post a more formal update in the coming week.

Thanks for everyone still keeping up and offering their insight!

Need more UVs.