ASA Filament Guide — The UV-Resistant Alternative to ABS

If a printed part has to sit outside for more than a summer, ABS is the wrong answer and PETG is a coin flip. ASA is the one that survives. I have the same ASA license plate frame on my car from the summer of 2024 and it still matches the color of the spool sitting in my dry box. An ABS version printed the same week went chalky and cracked by October.

That is the whole reason ASA exists: it swaps the butadiene rubber in ABS for an acrylate rubber that doesn't care about sunlight. Everything else about it (strength, stiffness, acetone smoothing, styrene fume smell that makes your garage smell like a model car factory) is almost identical. You pay a small price premium and you pay attention to your enclosure. That is the trade.

I print ASA outdoors every summer. Here is what actually holds up.

I run a Bambu Lab X1C and a P1S on my test rig at 3DSearch, and ASA is the material I reach for whenever a part leaves the house. Sprinkler manifold clips. A weather station bracket bolted to a fence post. Raspberry Pi enclosures for outdoor temperature sensors. A replacement trim clip on my wife's car that broke in a parking lot and that I refused to pay $14 for. They all still look the way they did on day one.

The parts I printed in ABS during the same period: yellowed, brittle, one of them snapped when I flexed it with my hand. The PETG parts held up better than ABS but the brackets with any real load started sagging in direct sun by the end of August because PETG softens around 70-80°C and a black part in a Texas driveway hits that easily.

That is the experience talking. Now let's get into why.

What most guides get wrong about ASA

Most ASA guides treat it as "ABS but better" and stop there. Two things they miss:

ASA is not harder than ABS to print. It is slightly easier. Warping is a hair less aggressive. Layer adhesion feels a touch more forgiving. If you have ever dialed in ABS on an enclosed printer, ASA is the same workflow minus a few headaches. People who say ASA is hard are comparing it to PLA, which is not a useful comparison because PLA is a toy material next to any styrene-based plastic.

The fumes are not "just a smell." ASA emits styrene during printing, exactly like ABS does. Styrene is on the IARC list as a possible human carcinogen. I don't care how tough your nostrils are: if you are printing ASA in a room where you sleep, or a garage where you spend hours, you need real ventilation, not an open window and a prayer. More on this below.

If your printer is a Bambu X1C or P1S, you already have carbon filtration. Run a stock ASA profile, seal the chamber, and you are 90% of the way there. See my ASA settings for the X1C and the P1S profile.

ASA vs ABS — the full comparison

Property	ASA	ABS
UV resistance	Excellent, no yellowing	Poor, yellows and embrittles
Tensile strength	40-55 MPa	40-50 MPa
Impact resistance	Good	Good
Heat resistance (Tg)	~100°C	~97°C
Warping tendency	Moderate-high	High
Layer adhesion	Slightly better	Good
Fumes	Significant (styrene)	Significant (styrene)
Enclosure required	Yes	Yes
Nozzle temperature	240-260°C	230-260°C
Bed temperature	90-110°C	95-110°C
Cost per kg	$20-35	$15-25
Acetone smoothing	Yes	Yes
Color stability	Excellent	Poor

The short version: if the part will never see daylight, ABS is fine and $5 cheaper. The moment UV enters the picture, ABS is a waste of filament and ASA is the right material. I keep one spool of ABS around for when I need acetone-weldable parts inside a project box. Everything else is ASA.

ASA vs PETG — the comparison people actually need

PETG is the material everyone suggests when someone says "outdoor." It is not wrong, but it is not the same tier as ASA.

Property	ASA	PETG
UV resistance	Excellent	Fair
Heat resistance	~100°C	~70-80°C
Impact resistance	Good	Moderate, can be brittle on sharp edges
Print difficulty	Medium-hard	Easy
Enclosure required	Yes	No
Fumes	Significant	Minimal
Outdoor lifespan	Years	Months to 1-2 years

PETG is fine for a flowerpot that lives on a patio and that you do not care about in two years. ASA is what you use when the part is structural, load-bearing, or bolted to something expensive. I have a PETG hose bib extension that has been outside for eight months and it is visibly faded and slightly warped from a few 100°F afternoons. Same geometry in ASA, zero change.

If you are choosing between the two for a real outdoor project, ask yourself one question: if this part fails, does something break? If yes, print it in ASA. If no, PETG is the lazy choice and that is fine.

Print settings I actually use

These are the settings I run on the X1C and P1S. They also translate well to any enclosed machine running a 0.4 mm nozzle.

Setting	Value
Nozzle temperature	240-260°C (I start at 250°C)
Bed temperature	95-110°C (first layer 105°C, rest 110°C)
Chamber temperature	40-60°C
Print speed	40-60 mm/s
Outer wall speed	30-40 mm/s
Travel speed	150-200 mm/s
Layer height	0.2 mm
Initial layer speed	20-25 mm/s
Infill density	20-40%
Infill pattern	Gyroid or Cubic
Wall count	3-4
Top/bottom layers	5
Retraction distance	0.8-1.5 mm (direct drive)
Retraction speed	30-40 mm/s
Cooling fan	0-20%, never 100%
Build plate adhesion	Brim, 6-8 mm

A few notes that matter more than the numbers in the table.

Kill the part cooling fan

This is where people ruin ASA prints. They come from PLA land where 100% fan is normal, they load ASA, they leave the fan on auto, and then they wonder why the layers split. Turn the fan off. For the first 2-3 layers, always 0%. For the rest of the print, I cap it at 15-20% and only for small overhangs and bridges. If the print looks a little ugly on overhangs but the walls are bonded, you are doing it right.

Bed temp is not a suggestion

105°C for the first layer, 110°C for the rest. I used to run 100°C to "save energy" and I wasted more filament to failed first layers than I ever saved. PEI sheet with a glue stick. The glue is adhesion promoter and release agent in one step. Don't use painter's tape, don't use hairspray, don't use a fresh PEI sheet with no glue. You'll either tear the sheet or pop the print off mid-job.

Enclosure temperature

40-50°C ambient is plenty. You do not need a heated enclosure. The heat bleeding off the 110°C bed will get you there if the enclosure is sealed. If you are running an open frame printer in a cold garage, that is a different problem and the answer is a bigger enclosure, not hotter ASA.

Enclosure setup without spending $400

If your printer doesn't have a built-in enclosure, you have options that work:

• IKEA Lack table build. Two Lack tables, acrylic panels, magnets or zip ties. Around $40-60 total. This is the Prusa community classic for a reason.
• Grow tent. A 2x2 or 3x3 ft grow tent is around $60, has a zipper door, and comes with ventilation ports that are perfect for running a carbon filter or duct fan. This is what I recommend to friends who don't want to build anything.
• Cardboard box. Works. Looks stupid. But a big Amazon box over a Prusa will drop warping by 80% instantly. Do not use this long term with ASA because cardboard and 110°C beds are not friends.
• Manufacturer kits. Creality, Prusa, Bambu all sell official enclosures. If you want a clean solution and the money doesn't matter, fine, but the grow tent works just as well.

The enclosure is doing two jobs: holding chamber temperature and containing the fumes. Both matter.

Fume management (do not skip this)

I am going to be blunt because I see too many people print ASA in a bedroom and shrug. Styrene is a real chemical, the smell is real because your body is detecting a real thing, and you should not be breathing it every day.

Your options, in order of how much I trust them:

1. Carbon-filtered enclosed printer. The P1S and X1C have this built in. For other machines, add an activated carbon filter to your enclosure exhaust. Replace the carbon every few months of active printing.
2. Duct it outside. A 4-inch inline duct fan from a grow shop, cheap flexible ducting, and a window. Best option if you cannot fully contain the fumes.
3. Dedicated printer room with airflow. Not the same room you sleep in. Not a shared workshop. A room with windows that you leave for the duration of the print.
4. Well-ventilated space with the window open. The bare minimum. Only for occasional prints.

Never print ASA in a bedroom, a nursery, or any room where someone sleeps. I know that sounds obvious. I know someone reading this will do it anyway. I am telling you now so future you doesn't wonder why you have a headache every morning.

Post-processing: acetone smoothing is still magic

One of the legitimately fun things about ASA is that it dissolves in acetone just like ABS. This means you can vapor smooth a rough layered print into something that looks injection molded.

My process: mason jar, paper towel on the bottom soaked in a tablespoon of acetone, print sitting on a small raised platform (I use a pill bottle cap) so it never touches the acetone directly. Seal the jar. Wait 20-40 minutes depending on part size and how smooth you want it. Pull the part out, let it cure for 24 hours in open air before you touch it too much, because the surface is tacky until the acetone fully evaporates.

This is how I finish automotive trim pieces. The difference between a raw ASA print and a vapor smoothed one is the difference between "I printed this" and "where did you buy that?"

Sanding works too, 150-grit through 2000-grit, but acetone is faster and gets into details that sandpaper cannot reach. Primer adheres well. Standard spray paint sticks without special prep. ABS/ASA cement creates chemical welds that are stronger than the layer bonds themselves.

Where ASA actually shines

Not every outdoor print needs ASA. Some things to actually print in it:

• Automotive trim and exterior parts. License plate frames, mirror mounts, trim clips, under-hood brackets that see engine heat.
• Outdoor electronics enclosures. Weather stations, garden sensors, outdoor camera housings. This is probably my most common use case.
• Drone exterior parts. Anything that lives in direct sun while the drone is on the ground between flights.
• Signage and lettering. Color stays true. A printed house number in ASA will still be the right shade of black in five years.
• Marine accessories. Dock fittings, small boat accessories, anything with salt and UV exposure.

Things you should not print in ASA: indoor decorations (waste of money, use PLA), load-bearing structural parts that need real strength (that is a job for nylon or carbon-filled composites), anything for food contact (see my food-safe printing guide, and spoiler, the answer is "no, not really").

My ranked ASA picks

I have printed all of these. These are not affiliate picks, these are what I actually buy and reload when I run out.

1. Polymaker PolyLite ASA. My default. Consistent diameter, prints on stock profiles without fuss, color range is solid, and the price is reasonable. If you asked me to grab one spool without thinking, this is it.
2. Prusament ASA. The most consistent ASA I have ever run. Every spool comes with a QR code linking to actual measurement data from that exact roll. Expensive but if you are doing a commission or a batch that has to be identical, this is the one.
3. Fillamentum ASA Extrafill. Premium European brand. Their colors are genuinely nicer than anyone else's. The "Vertigo" sparkle variants look incredible on outdoor signage. Worth the price for aesthetics.
4. eSUN ASA. The budget pick. Prints fine. Colors are a touch less saturated than Polymaker. If you are doing prototypes or parts that will be hidden, this is a good way to save $10 per kilogram.
5. 3DXTech ASA. Industrial-grade tolerances, if you need them. Overkill for most hobby use. Good for engineering applications where you care about exact dimensions.

Brands I would avoid: no-name Amazon ASA with five-star reviews and a logo that looks AI-generated. Diameter consistency matters a lot with styrene-based plastics because inconsistent flow plus warping tendency equals failed prints. Don't save $8 to waste a weekend.

Drying matters more than people think

ASA is not as moisture-hungry as nylon or TPU, but it does pick up water over time and wet ASA prints look rough with pitted surfaces and audible popping from the nozzle. If the spool has been sitting open for more than a few weeks in anything but a dry box, dry it before printing.

Method	Temperature	Duration
Filament dryer	65-70°C	4-6 hours
Oven (convection)	70°C	4 hours

Store dried ASA in a sealed container with fresh desiccant. In humid climates (I am looking at anyone on a coast), print from a dry box full stop.

Common mistakes and how to fix them

Part detaching from the bed mid-print. Bed temp is too low, no brim, or no glue on the PEI. Fix: 110°C bed, 6-8 mm brim, glue stick across the entire first-layer area.

Layer splitting on tall prints. Chamber is too cold or fan is too high. Fix: seal the enclosure, kill the fan, verify the top of the print is still warm to the touch when it finishes.

Corners warping and lifting. Enclosure not sealed, or part is too close to the edge of the build plate. Fix: center the print, close any gaps in the enclosure, consider a draft shield for large parts.

Ugly stringing between walls. Retraction too short or temperature too high. Fix: increase retraction to 1.5 mm on direct drive, drop nozzle temp 5°C, print a retraction tower and pick the cleanest result.

Gritty, rough top surfaces. Wet filament. Fix: dry for 4 hours at 70°C and try again.

Colors come out dull or streaky. Usually a pigment issue with cheap ASA. Fix: buy from a brand that lists the actual color data, or dry the filament first because moisture affects surface sheen.

Final thoughts

ASA is what ABS should have been all along. Same mechanical properties, same acetone trick, same print workflow, with the UV resistance built into the chemistry instead of bolted on with coatings and wishful thinking. The price premium over ABS is genuinely worth it the first time you pull an ASA part out of a summer of direct sun and it looks the same as it did on day one.

Get an enclosure, get ventilation that you actually trust, buy one spool of Polymaker PolyLite ASA to start, and run the settings above. You will be printing outdoor parts confidently by the end of your first spool.

If you are trying to find models that are worth printing in ASA, search 3DSearch for tags like "outdoor," "weatherproof," or "automotive." Want to see how ASA compares to the rest of my filament lineup? I wrote up my actual brand rankings and the full ASA settings for the Bambu X1C.