Filament vacuum bags myths/debates solved

[ArtyP]

Many people have different opinions on vacuum bags,

I bought some because they are cheap and curiosity got the better of me when I wanted to compare it to Sainsbury’s freezer bags that would tear if you looked at them wrong.

Myths/debates I set out to solve:

1. Putting silica gel in the centre of the spool seals it off and makes it useless
2. Vacuum bags don’t hold a seal and tear easily
3. water permeates through the bag

So I went off to test these starting with the first one

I first put a new bag of silica gel (I used the one that comes with elegoo filament because my loose silica gel has degraded so it can’t get under 30%RH) into the centre of an empty kingroon spool, since these are the only plastic spools I have empty ones lying around.

I had a hygrometer in the centre of the spool and on the edge of the spool.

At first the hygrometer in the centre read 64% and the one on the edge read 67%

minute 10: centre; 36% edge; 66%

minute 20: centre; 20% edge; 59%

minute 30: centre; 20% edge; 59%

minute 60: centre; 10% edge; 58%

24 hours: centre; 10% edge; 52%

48 hours: centre; 10% edge; 49%

next when I put the silica on the edge:

at the start the centre read 74% and the edge read 65% however the high reading may have been due to holding the hygrometer In my hand however the readings after 5 mins should be accurate but I can be treated as 65% for the start

minute 10: centre; 60% edge; 57%

minute 20: centre; 59% edge; 56%

minute 30: centre; 57% edge; 52%

minute 60: centre; 54% edge; 45%

24 hours: centre; 43% edge; 32%

48 hours: centre; 40% edge; 29%

from this we can see that despite diffusion meaning it should even out if there is even the tiniest hole it is still always much drier where the silica gel is located and I would consider this myth true since moisture on the wetter side of the spool likely went through the hole in the centre o the spool where filament is secured in at the start of the spool during manufacturing but when the spool is full this hole would be plugged and have many layers of filament in the way.

Myth 2.

I have used the vacuum bags for 1 week and none have torn and the bags are slightly thicker than ziplock bags maybe 1.2x as thick and these are much better than my supermarket own brand bags that would develop holes because it would crinkle due to its thickness of about ~1.4x as thick as cling film and the crinkle would make a tiny pinhole hard to notice just around the crinkle.

now comparing to the vacuum bags:

I tested it like a real world condition by putting the bags onto a surface ,with the bigger face facing up and down (micropore down and smooth up) , and sliding it 30cm to the side and leaving for a day.

I would do this every day and see if it lasts 7 days or if it doesn’t what day it fails at and if on the first slide then I will mark as failed.

The smooth wood is the wood in furniture that is treated and covered in a glossy coating so it is as smooth as plastic but not as thick as resin coatings.

The rough wood is similar to a fresh dry 2x4 on the side where it is not like a tree but rough enough to give a noticeable texture in between a textured pei bed that has spikes in the pale of the smooth bumps and a matt finish.

The new tarmac is just a fresh brand new tarmac driveway.

The ‘absolutely ancient Bri’ish road’ is like a poorly maintained old ridged concrete road like some found on semi private land between enclosed houses like in a cul-de-sac.

The first row is the sainsbury’s freezer bags and the second row is the filament vacuum bags.

smooth wood	rough wood	new tarmac	absoloutely ancient Bri’ish roads
Pass	4 days	2 days	failed
pass	pass	pass	5 days

In conclusion this gruelling torture test shows that the vacuum bags are very robust and that this myth is busted and it tearing is due to scrunching it up making stress points or due to leaving exposed filament ends which can tear when vacuumed, however the scrunching of the bag being vacuumed has not caused me any problem after many vacuum cycles so it is only if you scrunch it up into a ball that it could tear.

and also for my bags that I use under normal conditions without testing it or anything they are holding a seal very well and I have not had any problems however people who have had problems may be having seal issues such as using a finger to seal the bag rather than my meticulous method of sealing twice from one end to the other one each direction get the the edges whilst squeezing hard.

Myth 3.

I have been confused why my supermarket freezer bags had been only getting down to 30% even with desiccant that would reach 10% in a dry box and I had assumed that water had permeated through the bag due to the bag not being strong enough to resist the forces of diffusion when the inside was under 30%.

I had heard similar things about these vacuum bags so I had to test it out in some way or another.

Test method:

I started by putting some desiccant into the bag and sealing it shut whilst measuring the humidity halfway to the other side of the bag.

I used a container of the fresh loose desiccant I had left in a sealed bag with some filament for a long time so this was not degraded by regeneration cycles with the rest of the desiccant but I dried it once after I found it in the bag.

Note: using a different desiccant does not make this an unfair test because I am using the same desiccant throughout this entire test and it is only different to the other tests which we are not comparing to.

an image from the start

10 mins

20 mins

30 mins

1H

24H

It seems that water does indeed permeate through the bags.

Now when we have a problem we don’t just moan…

we moan for 10 mins then find a big brain solution.

Now I wanted to see if double bagging is as effective as a dry box.

double bag after 5 mins (this was the first photo because it took 5 mins to put the bags in each other)

double bag after 10 mins

20 mins

30 mins

1H

2H

24H

from this we can see that a similar thing happens with the vacuum bags and water is definitely permeating through because a dry box gets down to 10%RH with this desiccant in this container within 30 mins so water must leak in somehow.

In conclusion this myth is confirmed and double bagging is an effective way to store filament and will not take too long to fit one bag into the other if the bag on the inside is vacuumed unlike in my tests.

real life use on filament vacuum bags:

I have not needed to flatten the seal after vacuuming but I have sealed and vacuumed a bag with and without doing this however it may make a difference as the ring around the hole in the centre of the the seal becomes white after vacuuming indicating that the two sides aren’t pressed together and it turns dark blue after pressing with my fingers.

Despite not having issues with the seal the blue stickers are sometimes slightly misaligned so I would understand if others are having seal issues however if it is for every bag then it is likely due to user error.

The silica gel included with my bags turned out to be bentonite/montmorillonite clay and the bags looked similar to the bags that come in Kingroon filament which also was this type of scammy clay formed into balls to feel like silica gel just the packets were smaller in the bags.

The humidity indicator is not really worth it so I didn’t get mine with it as there isn’t really anywhere to put the humidity indicator card so it is pressed against the wall so there is no air touching it and also if it is sealed then it will always be low enough if it is double bagged with desiccant and shows no sign of leakage like ballooning outwards.

In summary we can see that to put this into practical use we know that you should,

use the desiccant on the outside of the spool

not have to worry about tearing as much but problems are more likely caused by incorrect sealing

double bag the spools with the one on the inside vacuumed but your choice on the outside

use your own silica gel if the bags are the white paper ones with bold black text.

[lkraus]

@ArtyP

Myths/debates I set out to solve:

1. Putting silica gel in the centre of the spool seals it off and makes it useless2.
2. Vacuum bags don’t hold a seal and tear easily
3. water permeates through the bag

1. I use these curved desiccant boxes. I tried a few similar designs, but the mesh areas were too delicate and broke easily. These fit nicely in storage bins, vacuum bags, and even in my Eibos dryer. Each one holds about 25g of dry silica gel, plenty for one or two spools of filament. I printed mine with nylon so I can just pop them in the oven for desiccant renewal.
   

   

2. I’ve not had any vacuum bags tear, but I am cautious when sliding the wide center of the spool past the seal. Cracks can develop over time, mostly from repeated flexing in creases.

3. Remove most of the air when sealing to also expel the moisture it contains, but don’t apply a hard vacuum. Large pressure differences only pull more moist air through the plastic. I look for just a slight concavity at the center of the spool. Also, folds in the plastic will be somewhat less tightly creased, which might extend bag life.

[blchandl2]

I have found that sliding the spool in and out of the bag damages the seal. You can reduce this by moving the spool relative to the bag such that the ends of the seal are diagonally positioned to the wide part of the spool top & bottom. Pay particular attention to the size of the bag as some brands are slightly narrower than others making this more of an issue. My last purchase of bags were these:

https://www.amazon.com/dp/B0DRJPMT7Z

I have not had any fail in over 6 months of use. They are larger which makes them mush easier to put spools in and out. The vacuum valve seems to be more robust than other brands.

[RetroSharky]

First of all, thank you for the great research work!

With this whole topic, I always wonder how many forget or don’t consider optimising the workspace. I don’t mean to overthink it though, just to keep an eye on it. For example, I adjust the room temperature and humidity, so that I can leave PLA filament out open for around four months. During this time, I will ensure that I have used it up. Please note that I am speaking for myself and it is clear that not everyone can optimise this. Don’t confuse facts - what this is not - with a simple personal experience report from me.

Nevertheless, it would be sensible to consider the workspace before investing significantly in drying and storage equipment. As I said, there is nothing wrong with either approach; I see them as a whole. Oftentimes, however, no thought is given to the workspace, but too much overthinking is given to storage.

We still need to talk about how the workplace can be optimised. Of course, if possible. Perhaps also the question of how much is too much, i.e., overthinking. Or, to be more precise, spending too much money without considering the bigger picture, including the workspace.

Unfortunately, there are few posts in forums or online about middle-range experiences, which is understandable because things almost always run perfectly in this area. Consequently, we only really see the two extremes: either someone spends a lot of money on the topic, or they don’t care about it at all and end up with misprints.

If I posted online - except here - that I had left the filament rolls open and exposed for four months, people would certainly leave nasty comments because they don’t understand that optimising the space can also help. Although I pay extreme attention to quality, for example when it comes to my miniatures, and produce really demanding prints.

Please also note: My comment specifically refers to PLA - not filament that absorb moisture like crazy.

[ArtyP]

hi thanks for your comment, I have moisture issues of stringing within maybe 3 weeks due to my house being high humidity and that is why I am researching vacuum bags however everyones experiences are different and if you can leave it open then why not.

I was willing to get vacuum bags despite not having much money to work with simply because I found one for £12 for 50 bags on sale on temu however I can’t find it anymore and I might be more expensive now.

edit: it may be this one [Printer Storage Bags] 3D Printer Filament Storage Bags Vacuum Kit, 3D Printer Filament Sealed Bags with Desiccants/Seal Clip/Hand Pump, 13.4x11.8 inch Perfect for Most 3D Printer Filament Storage and Keep Filament Dry

[ArtyP]

Thank you for your comment, when I say some people have the bags fail a lot I am referring to a few comments in the other bambu forum discussion on vacuum bags.

[ArtyP]

Hello and thanks for you comment, I normally use a stronger vacuum so that there is a crease in the centre of the spool and the spool is even being bent inwards just a little bit and have not had any damage to the spools of the bags.

The reason I vacuum it so tight is because that there is not much air already in the bag but the main point of vacuuming in my opinion is so that it expands outward if it tears.

[TomWS]

Thanks for the link! This should add an extra level of protection for my spools of TPU (PA if I ever go there).

[MaxThreeD]

Nice data, thanks for posting!

With regards to desiccant not being “connected” to filament inside the bag due to vacuum, I had the same thoughts with the center-mounted desiccant holders I use in my spools. I made some cupped spacers to go into the bags which provide some air movement between the desiccant and the filament on the spools. (I’m using alumina in metal powder shaker cans so it easy to recharge, and using the desiccant already in the spool seemed simpler than adding another type of container. I used PLA Tough+ for the spacers., very strong.)

Personally with those cheap little hygrometers I’d give 'em at least an hour to settle down before trusting anything they say (and even then with a grain of salt). Especially after holding one in my hand. Also to note is they’re not all created equal, especially with low humidity below 10-20% (and all are completely useless < 10%).

As far as bags, I’ve used various brands of the valve-and-pump style for years in the kitchen. The one with the simple flat, thin plastic valve are OK for a few uses, assuming they seal in the first place, but they really don’t last very long, especially with any “rough” treatment like being folded or dirty or moist. I’ve recently starting using the newer style valves with the rubber gaskets and plastic covers – these are by far more robust, and can even be cleaned if necessary. Also, way easier to get the pump lined up on 'em. Only real negative I’ve found is that they rely on being attached to the bag, which is a weak point in terms of strength and leakage (but no actual issues so far).

Oh and my Miele vacuum handle nozzle fits perfectly over those valves… like it was made for 'em. It is 1000x faster using a real vac than the little hand-held pumps. Heck it’s faster to suck the air out with your mouth!

@blchandl2

I have not had any fail in over 6 months of use.

YMMV, as they say… Used up a box of those so far with 50% failure rate, bought ~ a month ago (they seem to change their designs often). I’ve used another brand with ~10% failure rate, though the bags are a little smaller and not as easy to deal with (“Domivio” brand large size, https://www.amazon.com/dp/B0FPKNFSW7). Not saying that to knock the brand or your choice, just goes to show that the quality/reliability/practicality of these bags can vary quite a bit.

In at least a couple cases with both brands the leaks were probably my fault because a hole got poked somewhere. I’ve used other bags (for food) which are way thicker than either of these bags (eg. by Vesta Precision), with much sturdier zipper (tool required to close), but I can’t find any like that with the more robust valve style and large enough.

Cheers,
-Max

[ArtyP]

I’ve been thinking of using activated alumina since August but couldn’t afford it but now I have some arriving tomorrow and will provide an update on activated alumina in the vacuum bags

[user_1017524304]

Agreed with not over vacuuming the bags as to not have such a severe pressure difference and stress on the bags. Tremendous benefits doing it as you’ve suggested. I’ve also noted that Even though the bags from different providers look the same they don’t all behave the same. Using the same decadent and about the same time period with a good seal I’ve had my decadent go lavender to almost pink and other ones have stayed dark blue with the same setup. Fortunately I do check this stuff frequently.

[Minok1217]

In my case the space is what it is - an attached garage in the Pacific Northwest.

So it will be at ambient humidity and mild temperatures most of the year - which is slightly humid and cool on 60% of the year and dry and cool to room temperature 40% of the year. So given that, and that I’m not running a printing shop but rather hobbyist, I will often be stowing partially used spools for many months.

If using small desiccant packets I’d put one inside the spool and outside, solves that problem.

Like the double bagging idea to protect the vacuum bags from handling.

I’ll be testing to see how well bags work with the jar sealing attachment of my Nesco vacuuming system.