Can’t argue with that logic.
I have been wondering just how low the RH should be inside the storage container. I’m guessing as close to bone dry as possible. The wiki says that if the typical filament is stored in 20%RH, then it will only stay dry for 2 to 7 days:
https://wiki.bambulab.com/en/filament-acc/acc/sealed-box
Also, the filament storage box on display at that link looks like it requires much less 3D printing to host the filament spool than the cereal box I’m presently using. I’ll have to see if I can find that model at a good price and, if so, I may switch over to that type, or at least try one out for comparison. If anyone knows which cereal box it is, please post a link.
I have the same one as yours as I could not find the same as in the previous posts on the amazon european sites unless shipped from overseas and I just need the box not the complete kit. They have them now under the wildone brand name but it really depends on where you live. You can easily tell them apart by the 3 indents on the sides and the hexagon inprint on the top. I think this is better suited as it seems to have same width front to back contrarily to yours (or mine) which is narrower on one side which requires a specific spool holder as you experienced…
Logic 
Valid
Thank you
I did find one on amazon:
https://a.co/d/cRisKUU
but at more than 3x the price. 
A surprising number of spools, including the BBL spools, aren’t a smooth shot through the center, and that seems to thwart the universal adapters…
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For me as most of my filaments are just PLA or PLA + i dont suffer too much with “wet” filament but what i do is just store my filament in the zip log bag kits you can get from amazon
eSUN Upgrade Vacuum Kit, 10pcs 3D Printer Filament Vacuum Compression Storage Bag with USB Pump, Reusable Filament Moisture Proof Dry Vacuum Sealed Bags
currently on offer too with 25% off… comes with a USB vacuum pump also £14 i paid.
This is the model that BBL chose to use:
https://www.printables.com/model/835472-4l-cereal-filament-dry-box
The same fort of thing, but remixed for bottom support and ripple-fit should work with the Praxi cereal boxes.
I’m brand new to filament printing… if you keep them in the sealed plastic bags they spools arrive in, is that good enough? (Not worried about switching materials types just yet, just protecting my stock)
Unfortunately, no. Given enough time, the moisture gets in. I know this for sure because I had a bunch of factory sealed filament spools before covid and then I went on hitatus during the covid pandemic. When I resumed after covid, they were all soaked. All of them.
Second, most likely your filaments already have moisture in them, even if you just received them. I’ve done the experiment. Open a fresh spool, weigh it, then dry it, and then weigh it again. Even for PLA, generally it will lose 1 or 2 grams of something, which I’m assuming is mainly water. This seems to be true regardless of brand. I suppose one could take it even further and try to distill whatever the emissions are to prove whether or not it really was water. I don’t have the apparatus to do that conveniently, but if anyone here has, or know of anyone who has, it would be worth knowing.
Why might a fresh spool of filament already have water in it? 1. It might be a long while after manufacture, even if you just received it. or 2. apparently the manufacturers actually run filament through a trough of water to cool it off after the extrusion process. I know, I know. Seems like a bad idea, doesn’t it? So, they throw in a tiny bag od disiccant to avoid your suspicions and maybe because it helps protect a little against it getting even worse while in transit.
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I can wholeheartedly endorse that observation as being 100% true. That’s precisely why I began using moisture indicator cards in bags I reseal using a vacuum.
Here’s another observation that someone here noted, and I subsequently tested: Cardboard spools are moisture magnets in their own right. There is no justifiable reason why companies should use cardboard if shelf-life is a concern. While it aids the environment by biodegrading in landfills, it also introduces moisture into the bag, compromising shelf-life. I conducted an experiment with two empty spools, one cardboard and the other made of PLA, which never saw the dryer. I vacuum packed both empty spools and included a moisture indicator card. Within only a week, the paper spool’s indicator card started to change dramatically while the plastic one did not.
To further investigate, I started placing the empty paper spools in the dryer and weighed them. There was a considerable amount of moisture in the non-dried spools, ranging from 3 to 5 grams in some cases. While this moisture may not be an issue for PLA, most of my PETG filament comes on cardboard spools.
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Prusament is widely regarded as quite good. Yet, they too use a water bath to cool their filament after it’s extruded:
Now ask yourself this: why would they need to add rust-preventing solutions to the cooling bath? The filament is plastic, so it’s not going to rust. No, I think the reason is that it will pick up some of the water, and when it runs through your hardened steel hotend, releasing some of that moisture, they don’t want it literally rusting the metal in your machine. So, they throw in the rust preventative for that purpose? I don’t know. If you’ve got a better theory, make a post.
Likewise, they wouldn’t need an anti-bacterial if it was bone dry. Ask any biologist. Or NASA for that matter. But it makes sense if they know the filament has moisture in it. They don’t want it arriving moldy or rotten. That’s the uncharitable view. The more charitable explanation is that they suspect it might pick up moisture down range, sitting on your machine or wherever, and they don’t want ti getting moldly or rotten then, even if in that case it would technically be your fault and not theirs.
So, altogether, not ironclad proof it leaves the factory with water in it–a non-trivial amount that could support life or cause rust. Still, the evidence seems to point in that direction.
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Afaik, all industrial extruders cool filament in a water trough. The rust preventive is probably to stop the trough, fittings or rest of the mechanism rusting, although Prusa may pretend it is for the customer’s advantage. Wrt card board spools, they may in fact act as a desiccant, and help in keeping moisture from the bulk of your filament. If it is dried with the filament, and sealed in a quality vacuum bag, and compared with a plastic spool, all things being equal, there would initially be the same moisture in each bag. If the cardboard absorbs moisture, that is less for the filament. After you wash you hands, do you dry them in a plastic sheet, or something absorbent? I prefer plastic spools, but if commercially printing, disposal of them is a problem, very few of the recycling plants are set up for handling them. For hobby use, it is easy enough to re-spool , anyway. It all depends in what part of the world you are in.
I saw some guy on Youtube, trying to explain that fdm printed stuff was unsuitable for food safety equipment. He mentioned the lead* in the brass nozzle as being one reason. Most of the uk water service pipes were lead. On the same basis, if the filament is coated with rust preventive…
*There’s heck of a lot of nonsense out there. Brass is primarily copper and zinc, maybe with traces of arsenic, aluminium and lead. I guess arsenic and aluminium is OK.
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There is more lead to be exposed to by being in any building that has paint in it from before the 1980s. Many of the plastics they still use today contain small amounts of lead.
And we won’t even go into the obscene amounts of lead that were pumped into our environment (and still exist today) from the petrol/automakers before unleaded combustion engines were mandated.
One has to wonder how much trace lead could be found from food - touching plastic - extruded by a brass nozzle with trace amounts of lead in it. LOL
I thought the significant danger with FDM and food products has to do with bacteria living between the layers.
To be fair, PLA is one of the least hygroscopic filaments in common use. It is quite forgiving regarding moisture content… to a point.
But plastic bags are very permeable in the long run.
So your PLA left in a plastic bag in a more humid environment will eventually start to equalize.
I would assume vacuum sealing the bag will speed up the process.
Well, that’s the reason that’s most often presented, isn’t it? I’d reckon it’s more like very clever public relations. For instance, it’s well accepted that if your local bakery buys frosting in a 5 gallon bucket, that bucket has to be food grade and not simply an orange bucket from home depot, even if the orange bucket is smooth on the inside. Otherwise you’d risk whatever random chemicals are in the orange bucket’s plastic leeching into the frosting, after which the customers will gobble it down as part of their cookies, cake or donuts.
Actually, Lexi is correct. ‘Food Grade’ is a USDA term defined as the following.
The term “USDA food grade” refers to products that meet the standards set by the United States Department of Agriculture (USDA) for safe use in food production and processing environments. These standards ensure that the materials and products labeled as “food grade” are safe for contact with food and do not introduce harmful substances or contaminants.
Key points of USDA food grade include:
- Safety: Materials must be non-toxic and free from harmful chemicals that could contaminate food.
- Durability: Products must be able to withstand the rigors of food processing environments without degrading.
- Cleanability: Materials must be easy to clean and sanitize to maintain food safety.
- Compliance: Products must adhere to specific regulations and guidelines set by the USDA, including those related to hygiene and sanitation.
These standards are applied to various materials and equipment used in food processing, packaging, and storage to ensure the safety and quality of food products.
So if you ever noticed that certain lubricants such as the PTFE lubricant I have mentioned in other posts, calls out USDA Food Grade. What that means is that if the lubricant comes in contact with food and accidentally ingested, it is both non-toxic and free of any materials that might invite microbial activity.
Way back in my teenage years I worked for a food service company that was owned by a private equity company. We did everything by the book and that book took up 12 3" volumes of binders in our managers office. One particular thing I recall was as a lowly dishwasher(mind you I was 16 at the time) I was put through quarterly training by corporate who required us to come in early on a Saturday morning to be trained in food safety. One of the things that stood out was as one of the dishwashers, I had to inspect the porcelain dinnerware and make sure that the glaze was not compromised. If it was chipped or cracked, it had to be thrown away. The reason I was told is that once the glaze is compromised, bacteria can grow inside the porcelain and no amount of cleaning would prevent this.
Food grade filament only means it’s chemically and biologically safe, it does not mean that the 3D print meats the standard. For that one has to seal the end product to make it food grade.
Here is one company that provides guidance on making 3d printed products food-grade.
I agree with both of you. No disagreement here. I guess I was being too oblique, but what I meant was just that the filament industry would rather that we be talking about those bacteria in cracks reasons rather than wondering about whether their filament is even safe to handle because of what’s in it.
For instance, I just recently purchased Mitutoyo calipers, and it came with this note:
A lot of corrosion inhibitors are actually pretty toxic. What about the ones in the cooling water that your filament is streamed through? Who knows? And that’s just one type of thing out of probably many.
So, it came with a material handling sheet for a corrosion inhibitor that they applied?
Did they supply you with some of this “VCI Paper”?
Or are they suggesting that you must wear PPE and turn on an exhaust fan every time you use your calipers?
Yes, it came with the paper. It prevents corrosion without introducing any measurement errors. Mitutoyo recommends wiping off the calipers with a cloth before using them so that you don’t touch the residue with your hands. That’s where their advice ends. Probably some people keep the paper and store their calipers with it again after each use. I keep the calipers in a conditioned space, so I ditched the paper. It served its purpose already.
Anyhow, we’re getting way off into the weeds… Probably better to return to the original topic I think.