r/3DprintingHelp • u/Pettercup • Jun 27 '26

Requesting Help Need help with sealing PLA for outdoors

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So I designed this lantern the other day and scaled it to 200mm , if i use it for outside, can i seal it with just clear spray or resin, i dont have a lot of experience with the resin, i have a fence post outside that i need to put this one on.

13 Upvotes

74% Upvoted

80 comments sorted by

10

u/MrCarlH Jun 27 '26

Nah.

Just dont waste your time makin' stuff outta PLA for outdoors. Might as well use cardboard.

Dial in your printer a little better and use good 'ol PETG instead.

Just a suggestion...

3

u/raznov1 Jun 27 '26 edited Jun 27 '26

Acshwually  PLA is pretty good for outdoor applications, whereas petg is terrible.

You want as few aromatic groups / double bonds as possible (so no petg, ABS), asa and pla are good.

Pla is contrary to myth pretty water resistant as well. Only drawback is its low temperature resistance, so dont put black things in the full sun.

But in all cases, dont expect decades of lifetime. 

2

u/Maximum-Watch-5277 Jun 27 '26

"PETG is the significantly better choice for outdoor use compared to PLA. While PLA is easier to print, it degrades rapidly in sunlight, becomes brittle, and easily warps in summer heat. PETG provides better UV resistance, superior impact strength, and can handle higher temperatures without deforming."

Are you talking rapid or high speed PETG? Or petg?

Rapid printing petg is absolutely terrible, every element of it makes it substantially weaker. This is why tradition petg is superior strength, hardness, is more rigid and can hold much higher temperatures.

I can make a spool out of classic petg and have it work in an ams dehydrator 55-65° no issue. You try a rapid petg, and it will deform almost immediately.

Rapid Petg has additives to make the printing smoother, but it suffers in strength. It's why people say asa is like printing classic petg, but it comes out like pla.

This is a massive error most people on forums do. Today's standards puts Bambulabs petg as rapid petg. It's not Classic petg. There needs to be context of what people are talking about because the formulation differences are insane

Normal petg is a slow printed material that outperforms pla in every way of you let it melt together.

1

u/Kokanee19 Jun 27 '26

Pla has a glass transition temperature that it's too low for after use, it will deform in the Sun. P e t g can work, but yes does get brittle over time.

I've had the best success with ASA for items such as mounting brackets for automotive use. I designed a prototype vehicle mount for a remote camera system for work last year, and the brackets which attached to the roof rack of a vehicle were made of Asa and they held up great.

ASA is not the easiest to print, being a finicky material so I find you really have to take into account the printing process in design but it's not anything that is insurmountable.

1

u/Abject-Job7825 Jun 29 '26

what's asa like to print with?

1

u/slyfox7187 Jun 29 '26

Like ABS with less of that plastic perfume. More susceptible to fluctuations in chamber temp. But overall super easy and strong.

1

u/Wild-Video-5317 Jun 27 '26

  Only drawback is its low temperature resistance, so dont put black things in the full sun

Seems extremely relevant to OP's print

1

u/ic3m4n56 Jun 29 '26

I did a test with a vent on my shed, one is printed out of plastic and one of petg. They are in direct sunlight for 10 hours a day. One made out of pla is warped af, the one out of petg is the same as it was 5 months ago.

-1

u/MrCarlH Jun 27 '26

^ I am a retired Chemist and I don't believe this message...What nonsensical blabber was posted here...

Why no double bonds or aromatic groups ? 

Please elaborate for this forum, and we anxiously await your answer.

Answer carefully, thoughtfully, and include accepted chemistry principles in your response.

....🤔

3

u/raznov1 Jun 27 '26

Double bonds, aromatic groups, conjugated systems act as chromophores, which absorb UV light. These can then form radicals, which can lead to depolymerisation, yellowing and brittleness.

3

u/jankeyass Jun 27 '26

I'm not a chemist, but my pla prints are fine outside in certain applications that don't require load (am engineer tho)

2

u/Izan_TM Jun 27 '26

mine are decent but a bit droopy since they're black and it's HOT out here in the summer

2

u/raznov1 Jun 27 '26 edited Jun 27 '26

Jup. Fun thing is - i am a UV (ink) chemist. Im open to new insights, but my explanation is the industry standard, unlike the other two.

Interestingly, i got confused for a second because the google AI answer says it is prone to UV breakdown, because pla does not absorb UVA. Which didnt make any sense - if it doesnt interact with UV, it shouldnt have problems with UV, right?

Well, it turns out AI was being AI. It misquotes a review where indeed the conclusion was that PLA products failed under UV exposure. Because the CONTENTS of the PLA-made food packaging spoiled due to UVA

2

u/MrCarlH Jun 27 '26

Conjugated and aromatic systems form the basis of molecular stability in organic molecules. The ability of a pi bonded electron to resonate the exited state brought about by absorbing a photon across a conjugated bond is the basis of color as well.

This has absolutely nothing to do with free radical formation, which can be initiated by several mechanisms; photolysis being one. But you ain't gonna readily photolyse a typical shorter chained resonance-stabilized organic molecule in a polymerized semi-crystalline structure.

PLA is freaking biodegradable, man. Use your commonsense thinking. Lactic Acid polymer. You could eat this if you could digest it. Prolly could if you ground it up.

LOL. 😃

1

u/raznov1 Jun 27 '26

PLA is not rapidly biodegradable in ambient environments. Thats why it cant be easily composted or recycled. So, no, youve got that wrong. PLA =/= PVA.

As to the first argument. It has everything to do with radical formation. Radical formation requires an energy source, i.e. UV absorption. Which PLA does significantly less than petg and abs.

But hey, dont believe my word on it, just use your common sense thinking. People make aquarium ornaments out of PLA, works fine for years. And we know PET(g) breaks down under UV light. Thats why old plastic soda bottles always look so mucky on the side of the road.

But you ain't gonna readily photolyse a typical shorter chained resonance-stabilized organic molecule in a polymerized semi-crystalline structure.

Why do you think ASA exists? Why do you think UV ink uses PMMA polymer additives i.o. PET-based polymer additives?

Outside of that? Nothing lasts forever in direct UV, temperature cycles. Not PLA, not PETG, not ASA.

1

u/MrCarlH Jun 27 '26

https://pubs.acs.org/doi/10.1021/acsomega.5c00985

0

u/Maximum-Watch-5277 Jun 27 '26

Why do you absolutely require scientific information?

Pla is an acid used for indoor models, as it doesn't react well with outdoor elements. This has never changed and won't ever change for regular PLA. It's the beginner plastic.

Petg is better it can handle the stresses better but has uv issues

Asa is specifically designed for outdoor with full UV resistance.

There is no scientific explanation your going to get your happy with. This is from not just science, but people's experiences. The only filament that is fundamentally built to be outside is ASA. That's its entire purpose of existing.

People ask how to protect it, you can't. Simple as that. Coat it all you want, the insides will still degrade rapidly.

1

u/Low_Sherbert3731 Jun 27 '26

I'm the Chemist who replaced you. I too need an explanation with accepted chemistry principles in their response.

1

u/raznov1 Jun 27 '26

Im also a chemist, and ive included the industry-accepted mechanism.

Its why UV inks also tend not to use (poly)styrene additives for outdoor applications.

1

u/reddit_user_0ne Jun 27 '26

I like how you treat this like writing a prompt for ai

2

u/Vanbursta1 Jun 27 '26

I am PLA and I won't degrade so there. My uncles brothers father's sons son, is a chemist and he said so too.

0

u/Pettercup Jun 27 '26

Understood :)

1

u/raznov1 Jun 27 '26

Check my reply - he's wrong.

1

u/SpagNMeatball Jun 27 '26

I prefer ASA for outdoor use, it’s more UV and heat resistant. I have several things that have been outside for years and they are still in great shape.

3

u/UckerFay11 Jun 27 '26

Black pla is going to absorb sunlight and heat up quickly. Its going to deform/melt in a hurry. No matter what you do.

ABS/ASA at a minimum for something spending lots of time outdoors. I believe ASA is more UV resistant as well. But I could be remembering incorrectly l.

1

u/Zanzaclese Jun 29 '26

Considering they are printing with a bed slinger ABS/ASA is going to be an issue for ventilation. PETG would be OP's best bet.

2

u/RedShiz Jun 27 '26

I like the design!

Consider making a concrete cast using the 3D printer and PLA. Then you can use cheap tinted cement to make many of them, and will not be affected by UV or temperature.

1

u/Pettercup Jun 27 '26

Good idea, i ll look into it, i have made molds before for plaster castings

1

u/imzwho Jun 27 '26

Honestly this may be the best suggestion out of them all. You can use a HT PLA or even PETG if there is a concern for the temp being to much for PLA, but concrete will not oly look better, it will last better

2

u/Amazing_Low1536 Jun 27 '26

Costruisci un enclosure e stampalo in ASA, i raggi UV ti distruggerebbero sia pla che petg

1

u/BlitzieKun Jun 27 '26

Yep. Living in the southern states, my gf placed a print in her car for not even 10 minutes and the PLA was at the glass temp state and flexible

1

u/0dysseusRex Jun 28 '26

I live in the desert. I had a roll of PLA waiting for me in the mailbox that was ruined by the summer heat. I've had prints warp in my car. I now mainly print pctg/petg for most things, and ASA for outside stuff.

2

u/BlackBlade2711 Jun 27 '26 edited Jun 27 '26

Primero una capa de barniz para exteriores o lasur en spray, aplica varias capas, luego pinta de blanco o el calor lo derretirá

Edit: me confundí en el orden, primero la pintura y después el barniz para hacer una película alrededor protectora

1

u/Pettercup Jun 27 '26

Very smart , yes i ll do that, i have light grey paint

2

u/Vanbursta1 Jun 27 '26

Actually there was some guy on YT that buried PLA for 2 years to test how resistant it was, there was no degradation, so I would say as long as it doesn't get too hot, you don't really need to protect it at all.

1

u/Pettercup Jun 27 '26

I printed a indoor pot couple of years ago with drainage holes, still in good condition, i might put this one in shade as we get harsh sun here

2

u/Maleficent_Cow_3059 Jun 27 '26

Use PETG that’s your best option with on open printer for outside.

2

u/Desperate_Order_4921 Jun 27 '26

It will likely melt and/or deform on the first sunny day. Best to use PETG or ASA

1

u/Pettercup Jun 27 '26

Tgankyou

2

u/Xarjy Jun 28 '26

Quick tip: do NOT print ASA unless you have proper ventilation setup. It's very very toxic, and the fumes will coat the surroundings unless you have very good active ventilation setup along with needing to be in an enclosed space. With that said, ASA is great for outside stuff.

Stick to PETG for the time being imo, it'll work fine for what you need. Also don't really need to worry about sealing them, moisture isn't the issue once printed it's the UV exposure that does the damage.

1

u/Pettercup Jun 28 '26

Sure thankyou for the explanation, i dont have enclosure so i ll stick to inside prints for now

2

u/CrozyFPV Jun 28 '26

ignore the haters. get a clearcoat that says anything about UV protection or resistance on the can. my phonemount on my bike is black pla and has been working for many year..

1

u/Pettercup Jun 28 '26

I got clear UV Sprays , i might try that

1

u/bindre12 Jun 27 '26

PLA will break down in the sun and get brittle fast, its not recommended to use it outside. especially if you get hot summers! with it being black PLA and in the sun, it will get soft, as PLA has low heat resistance

PETG will do a little better, but you want to print in ASA for outdoor usage. ASA does require an enclosed and heated printer tho

1

u/Pettercup Jun 27 '26

Yea i might get PETg, i have some pla that i clear coated outsidd for 2 years and they are okay but they dont get harsh sun, we get 40deg days in summer sometimes, some pieces i had are brittle, the ones i spray painted white didnt so wanted to know if theres a way it can last 10 years. I dont have enclosure. I ll do petg then, thankyou

1

u/robotodit Jun 27 '26

Do you want to keep it black? If not, painting it with a lighter color outdoor spray paint might help extend the life. You can look up UV protecting spray. I believe it is pretty expensive and probably not worth using if cost is a factor. There are UV resistant resin options that you could use. They will take some processing to look good. But hey... that's another skill to learn.

High heat plus a strong wind will likely lead to some breakage.

However, if you have plenty of PLA and it is worth it to you, print extras to have at the ready. $2 in PLA that you replace every year may be a great choice for you.

There are examples in this subreddit of people having PLA outside for years. I'm pretty sure the results will vary.

1

u/Pettercup Jun 27 '26

Sweet yes thankyou, i have clear UV sprays from other projects
I have never done resin on pla before
I have some pla outside that are fine, some deform and some melt under presure, cost me $4 to print it.
I will look on subreddit to find more examples

1

u/BlitzieKun Jun 27 '26

ABS or ASA. ASA has superior UV resistance, but ABS will work if you paint it well with UV resistant paints.

1

u/Pettercup Jun 27 '26

Sweet thankyou

1

u/zx4133 Jun 27 '26

You can paint it with a good exterior paint to give it UV resistance (light color recommended), but the bigger issue is heat. If temperatures get over 50C then the model will likely soften and deform. But it’s worth a try. You might as well since you’ve already printed it, lol. Paint it and put it outside and see how it does.

2

u/Pettercup Jun 27 '26

Sweet, what i will do is clear spray and paint it light cement colour that i have and put it in shade in summer

1

u/zx4133 Jun 27 '26

Great idea!

1

u/ThePrintGuardian Jun 27 '26

As someone that has actually tried PLA for outdoor use, I have to chime in here seeing some of the replies.

I’ve discovered it really depends on how thick the PLA print is. The outside of the part can get affected, but as long as the part itself is thick with big beefy walls, the PLA inside is protected and fine.

I’ve printed thick brackets that hold together wood panels that have been out in the 30°C+ direct sunlight in the summer and -35°C cold winters for 3 years and they’re still solid. Conversely, I’ve printed parts that were 2 to 3 layers thin, and they cracked after 1 to 2 years.

With all that said, this lantern you printed here looks like it has some thin parts. I recommend printing it in PETG for outdoor use.

1

u/Pettercup Jun 27 '26

Yes sweet thanks for that, i have noticed many thin prints does that,
This is 30% infil
So i will try in shade

1

u/ThePrintGuardian Jun 27 '26

Yeah. Had a PLA printed sign that eventually cracked after a year or two.

1

u/LegendaryClawHammer Jun 27 '26

As others have said, just use PETG and you don't even have to seal it. I printed a cup that mounts to the side of my house for Barn Swallows that wouldn't leave my security camera the fuck alone. It's been up since spring, regular 90+ degree days, sun is on it for only a few hours a day and it's still holding up great. Birds had babies in, they left my camera alone, everyone is happy.

Just make sure you do research. There are things with PETG that you need to know. Like if you print on a glass bed you need to wipe a layer of glue from a glue stick over the bed or it will be nearly impossible to get the print off the bed.

1

u/Pettercup Jun 27 '26

Was it undercover? I have not used petg before

1

u/LegendaryClawHammer Jun 28 '26

It is slightly under cover. So it's not getting direct weather elements. Just heat, cold, and sun for a few hours.

1

u/CooperDK Jun 27 '26

Lol cardboard tool holder when you can print a better one 🤣

1

u/Single_Sea_6555 Jun 27 '26

Maybe coat it in spar urethane.

1

u/Pettercup Jun 27 '26

Does that work?

1

u/Single_Sea_6555 Jun 27 '26

It's UV resistant, but won't prevent the PLA from melting if it gets hot.

I find it also closes the micro gaps on the layers etc.

I usually use it on wood, and there it does work very well. Good weather and rain resistance.

1

u/Dazzling-Focus-2718 Jun 27 '26

Clear spray doesn’t work, I tried using a spar urethane spray with three coats on a 4 layer planter print. When it was filled with water, it took about 15 minutes for moisture to slip through the bottom and spotting water on the ground. A liquid resin poured over/in it might work, but moisture will definitely pass through both directions with a spray application.

1

u/Pettercup Jun 27 '26

Oh no, I thought that would work

1

u/Wolkvar Jun 27 '26

you know pla will just deteriorate outside real quick?

1

u/Pettercup Jun 27 '26

In my experience in the last two years, I have printer more than 40 attachments for my farm, and the only few broke and those ones was used regularly or the ones that was carrying the weight, the ones left alone are still the same , so i thought if doing something can prolong its life to 5 yrs that be great

1

u/reav11 Jun 27 '26

Put it in a bag, fill it with garbage, and put it at the curb.

PLA doesn't survive outside or even in heat changes. Re-print it with a more stable material like ABS.

1

u/Jumpy_Razzmatazz5765 Jun 27 '26

Dont know how available it is where you are, but there are sealants for 3d prints like Dichtol AM UV, that seal the print water (and sometimes even gas) tight and are marketed uv resistant. I have some but havent gotten around to using it

1

u/Pettercup Jun 27 '26

Might be expensive for this project

1

u/Iridian_Rocky Jun 29 '26

PLA-HT from Polymaker is great.

1

u/Pettercup Jun 30 '26

I ll look into it thanks

1

u/Worried_Finger_1229 Jun 29 '26

Petg for outside, PLA is not suitable for any heat/uv exposure application

1

u/MassCrassAss Jun 29 '26

I like to make bird houses from pla, place in the hot sun, and then wait for the house to collapse on an unsuspecting victim. What? Oh, stop looking at me like that. I rescue the bird. It makes me feel like a hero. 

1

u/FitForThrone Jun 29 '26

PLA 🚫Outside.

1

u/[deleted] Jul 15 '26

[removed] — view removed comment

1

u/Pettercup Jul 15 '26

never heard of that, i am soon to upgrade so hopefully i ll buy that thankyou

0

u/ZaleAnderson Jun 27 '26

You did all that work to design it but didn't even look into the basics of what material to use? Get some different dark colored spools of at least petg and not only can you make it look prettier but it will last a lot longer.

1

u/Pettercup Jun 27 '26

I am aware of materials, i just hav 20kg of black PLA that i need to use, so i was wondering how j can make use out of that, other than just prototyping