So you are convinced that that factory-sealed filament is dry?

[Olias]

We frequently see posts asking, “Why does my print surface have [Insert Artifact Name here]?”

And just as often, someone replies: “Dry your filament.”
What usually follows is one or more familiar assurances:

1. “It was factory sealed.”
2. “I had it in the dryer for X hours.”
   — But unless the spool was weighed before and after, how can anyone say moisture was present—or removed?
3. “I live in Antarctica or on the ISS—0% humidity here ”

What’s rarely done is a basic scientific approach:
Measure → Dry → Measure again.

Here’s a clear example that happened to me today. Same spool, printed before and after drying. No other variables changed. One surface is smooth, the other pitted:

Sorry for the crappy image, black is so hard to photograph and there was a lot of dust in the air, the negatively charged print clearly was attracting dust even though I used and air can to spray it off.

---

This was a brand-new spool:
Before drying: 1161g
After drying: 1154g
That’s a 7g loss—just 0.60%.

Worth noting: it was a cardboard spool, and blank cardboard spools alone can shed 3–5g of moisture. Plastic spools remove that variable, but most budget brands use cardboard. I’ve tested that myself with empty spools that I placed in the dryer and can confirm this.

This filament was 3DJoHor PLA—$10–$13 per spool on Amazon. It came in a 2-pack; the other spool had no issues, so that might suggest that even during the manufacturing process, there may be variables in moisture.

The brand isn’t the point. Similar results have been seen with Elegoo, Anycubic—even factory-sealed Bambu Silk that I’ve posted previously(see below):

Truth be told, I assumed the problem was something else. But I tossed the spool in the dryer before I went to bed, and when I printed again the next evening—same model, same Orca profile, literally hit “send” on the same screen—the difference was obvious.

Would I have believed that a mere 0.60% weight change could fix it? Probably not. But here we are. The only thing that changed was moisture content.

— — — — — — — — — — — — — — — — — —

So next time someone insists their filament is “definitely dry,” the fair question remains:
Was it weighed before and after drying?
If not, the evidence might still be sitting right there on the print bed.

[Fr33lab]

It’s a good point. I always measure and note the weight before and after drying.

What is really helpful to understand why drying is so important: Out of 1 g (!) under standard conditions you will get 1.673 l (!) of water steam! You do not want to have this amount of water vapor in your print. It means a 100g print includes 167ml “air” (= no filament at this point) or imbededded steam.

My average result for printing is around 2g, so even the double of my example above.

[Qjo]

The only filament I can 100% say with confidence is dry when it gets to your door step is SirayaTech.

[lkraus]

I agree that weight is the only reliable indicator of filament moisture. Up until last month I would also have said that every roll of new filament I’ve bought came with at least two to eight grams of water.

I’ve since bought five spools of Jayo PETG, three of which lost zero weight after six to eight hours of drying. The other two have not yet been opened, but I will still weigh and dry them before use.

[RippeyFamily]

It is never dry, or that’s how I view it. Been burnt a few times on first print with new sealed spools. So every one goes into my dehydrator before use. I can store about 9 to 12 in there, so I don’t even bother to weigh before or after.

[Bullocks]

Every spool gets a 6-8hour pass at 50C. I have my dryer hooked up to solar so I am encouraged to just do it to use the free energy.

If the first print is garbage, then I weigh, dry per filament directions, weigh.

I will say that in the past, I’ve trusted (and not been let down) by companies who put their stuff in those silvered mylar bags.

[RocketSled]

The plastic bags that filament ships in is far from hermetic. Diffusion occurs, stuff outside can get in and stuff inside can get out. You don’t know how long or under what environmental conditions the filament was stored. So even if it went in to the bag dry, it might not be by the time you get it.

In addition, how dry it can be depends to a significant degree on how dry it was going in to the bag. Unless you know your filament manufacturer uses environmental controls to manage moisture absorption during their filament manufacturing and packaging process, the filament will have varying levels of moisture from the factory’s contribution.

The little pouches of desiccant that are usually included with the filament are more placebo than a guarantee of dryness.

You know you’re going to print. You know you’re going to be unbagging a new spool for that print. Throw the spool in your dryer the day before you expect to start printing.