Does PLA Filament Absorb Moisture? Taking a Closer Look

When planning your next 3D print, you’re likely paying attention to factors like build time, materials to use, and the design of your piece. However, one element you should also think about is moisture.

Although 3D prints can be relatively resilient, some materials like PLA will absorb water over time. In some cases, the moisture can ruin your prints, forcing you to start over.

PLA is a hygroscopic material, meaning that it absorbs water from the air. So, if you’re printing in a humid environment, you’ll have to worry about this problem far more than you would in a drier climate. The time it takes for PLA filament to get too moist depends on various factors, but if you store the material for a day or two, it will likely become too wet for printing.

Although PLA water absorption can be a problem, it’s not the end of the world. Let’s take a closer look at this issue and how you can adapt accordingly.

How Long Does it Take For PLA to Absorb Moisture?

Fortunately, PLA loses much of its hygroscopic tendencies after printing it. So, while you have to be careful when storing your PLA filament, you don’t have to be as vigilant once your piece is finished.

On average, PLA can absorb up to 40 microns of water over 150 hours. However, the filament has to be in a highly humid environment for this to occur. So, if your storage cabinet is pretty dry, you don’t have to worry as much. That said, it’s never a good idea to store PLA filament in the open air at all if you can avoid it.

What Happens When PLA Filament Absorbs Moisture?

Wet filament leads to uneven and messy prints. As the printer melts the material, the water evaporates, creating small bubbles in the plastic. As your printer is working, you’ll notice tiny bumps along the surface.

Even if your PLA filament only has a little water inside, these bubbles can be pretty prevalent. The wetter the material, the soggier the results. In extreme cases, your piece might look like it’s melting and won’t dry correctly at all.

Another issue with wet filament is that it can clog the printer itself. Since the material won’t dry quickly, it will stick to the printer tip and get stuck. In a worst-case scenario, you might have to replace the whole part.

Comparing PLA Moisture Absorption to Other Materials

Unfortunately, all 3D printing material is hygroscopic, so you can’t just switch to something else and avoid this problem altogether. However, when compared to other options, PLA filament is in the middle of the pack – it doesn’t absorb water too quickly, but it does get wet faster than some other filaments. Here’s a quick breakdown of how PLA compares:

  • PVA – If you’ve used this filament before, you may know that it’s completely water-soluble. So, PVA works for building structural supports since you don’t have to cut them off afterward. However, storing PVA is challenging because it doesn’t do well in humidity at all.
  • Nylon – Once you’ve created a 3D part with nylon, the material is surprisingly rigid and durable. Unfortunately, nylon can become unusable after just two hours when exposed to a humid environment. Read more about the best nylon filaments.
  • ABS – This plastic is pretty resilient and far less hygroscopic than its counterparts. You should still store ABS in a dry, airtight container, but it won’t get too wet if you leave it out overnight by accident. Read more about PLA vs ABS.
  • PETG – This material probably absorbs water the slowest, but that doesn’t mean you can just leave it out. Overall, you should keep all of your 3D printing filaments in a dry container until you’re ready to use them. Read more about PLA vs PETG.

How to Minimize Moisture Absorption With PLA

Fortunately, preventing wet filament is a pretty straightforward process. Just follow these tips, and you shouldn’t run into any problems when printing:

  • Use an Airtight Container – If air can get inside, water can too. Ideally, you can buy an airtight canister with a spool and an opening at the front so that you can just pull out the filament when you need it.
  • Use a Vacuum Sealer – If you have to open the container to remove the filament, air will get inside. One way to minimize water absorption is to vacuum that air out immediately.
  • Use Silica Gel Packets – These packets are excellent moisture absorbers. You might even have a few lying around from various purchases (i.e., shoes or beef jerky). If you don’t have extra silica packets, you can buy them online. Just remember that they eventually go bad, although it will take months or years, particularly if you follow the other tips as well.
  • Put Filament Away Immediately – You need to run a tight ship when 3D printing. Make sure that you put your materials away as soon as possible once you’re finished. Otherwise, you could wind up with some wet filament.

Can You Dry Moist Filament?

EIBOS Filament Dryer, 3D Printer Filament Dry Box with Fan, Adjustable Timer & Temperature Humidity Control, Compatible with Nylon PVA PLA PETG TPU 1.75mm 2.85mm 3.00mm, Storage Box
EIBOS Filament Dryer, via Amazon

Yes, you can dry your PLA filament if it’s already wet. There are a couple of ways to do this, including:

  • A Filament Dryer – If you’re serious about 3D printing, you might want to have secondary devices to keep your materials bone-dry. These machines are relatively affordable and work well. However, they’re only designed for one purpose, so you might not need to make such an investment.
  • A Food Dehydrator – You might have one of these appliances sitting on your kitchen counter already. If so, you can toss some wet filament inside to dry it.
  • The Oven – The simplest and most accessible option is to lay the filament on wax paper on a cookie sheet. Be sure to bake the material at a relatively low temperature so that it doesn’t melt. You can bake PLA at about 100 to 120 degrees Fahrenheit for at least four hours (depending on how wet it is).

3D printing requires diligence and planning, so you need to ensure that you don’t waste time and resources with wet filament.

Overall, PLA is a pretty stable material, but you can’t afford to be careless with storing it.