Filament storage bags

[mawyatt]

Reason for question arrises from some limited knowledge about humidity. A little story behind this, a former professor colleague moved to Northern Arizona University for medical reasons. We visited him and met many of his graduate students and they were working with a NSF grant to study forestry effects and had developed remote devices for collecting data that were attached to trees. They were failing in the field due to humidity effects but were in "sealed" plastic boxes, altho a couple failed because bears liked to chew on them

When the data was presented we immediately knew why they were having problems. Told them to drill a small hole in the bottom of the box to allow it to breath and place a Gortex fabric over the hole to keep insects out. Gortex allows breathing but prevents liquid water from flowing. Water molecules are smaller than the general atmosphere made up of mostly Nitrogen, but as N2, so unless something is truly hermetically sealed water molecules may enter as they are smaller than N2. Allowing this breathing by means of the Gortex fabric will keep the internal dynamic humidity lower than sealing the box where the water molecules enter but don't leave during the large temperature excursions the box experiences in the forest environment and condensation takes place and affects the electronics. They followed our advise and had no more condensation problems, altho the bears still like to chew them up

So question is, do the vacuum bags for filament actually work as well as one might think? Seems possible that water molecules would be drawn in by the lower internal bag pressure and build up in the sealed bag. The desiccant will of course absorb the small amount of intruding water molecules and keep the humidity low and this works well for the factory sealed bags which start with new desiccant. However, it seems that if a vacuum bag is used with a weak desiccant that over a long term and with some temperature extrusions the internal humidity could be higher than if the bag were just at normal pressure and not at a lower pressure to help draw in the water molecules??

Since starting 3D printing a few years ago we've accumulated some "open" filament, mostly PLA and we are in Florida USA where humidity is a constant problem. We've stored opened filament in large plastic boxes with bags of desiccant, lately been putting the open filament in Zip-Loc bags with desiccant, then into large plastic box. We are relatively new to 3D printing, have little long term experience with filament humidity effects, not sure if our method of short term storage is effective and considering the vacuum bags.

What are others experience with vacuum bags??

Best,

[Jeroen3]

I toss the bags, they're annoying. But if it's all you have.
When properly vacuum sealed they work, because if moisture goes in, the vacuum has failed.
The little silica pouch is for transport. It's very poor at absorbing moisture.
Re-zipping the bag with the pouch is better than nothing, because the filament itself is hygroscopic itself it will limit the amount of moisture to that what's in the bag. Meaning it will not get any more worse.
The bag will not breathe because it will move with pressure changes, the problem with the hard plastic bins in temperature and pressure changes is that the box does not breathe. Hence the need for the breathing hole or it will find a way!

Now, I drove to Ikea and got a few of the largest SAMLA bins to stack spools in. Add a chemical dehumidifier, which lasts years because the box volume is small and the absolute humidity can't be very big. And I have storage for filaments. The problem is this storage is finite and filament mulitplies...
This keeps spools in dry atmosphere, available at hand, without hassle of the bags. It not an indefinite solution, but filament is a consumable. At least it should be.

If I need a high quality print an doubt the filament I put it in the dryer for a few hours.

If you're in a significant humid climate you can take a look at the guidelines for moisture sensitive electronics parts, maybe even add those little "bake before use" cards. 
The Pick and Place podcast have an episode on this.

[mawyatt]

Thanks for the information. The IKEA SAMLA boxes are really good, been using them for all sorts of storage, electronics and otherwise for many years now. They've held up well over time, without becoming brittle nor yellowing, good value!!

Best,

[jpanhalt]

In our microbiology lab, we chose tape for keeping petri dishes securely closed based on permeability to various gasses -- namely CO2 and O2.  I no longer have that data, but this link may help: https://www.hindawi.com/journals/ijps/2012/302029/

In brief, many thin polymer films are permeable to various gases, including water vapor.  The mere fact that filament absorbs it is indirect evidence of that.

Glass and thicker plastic is safe so far as I know.  Thus, a large glass dessicator may suffice and be even better with a light vacuum applied.  If you use a vacuum, be aware of the dangers.  Using a drier (e.g., Drierite, calcium sulfate) is safer.

[BlackICE]

How about mylar vacuum bags?