Activated Alumina For Desiccating Your Filament

A man in a red plaid shirt draped over an olive t-shirt holds sandpaper in one hand an an aluminum tube filled with white beads in the other over a wooden table.

When you first unwrap a shiny new roll of filament for your FDM printer, it typically has a bag of silica gel inside. While great for keeping costs low on the manufacturing side, is silica gel the best solution to keep your filament dry at home?

Frustrated with the consumable nature and fussy handling of silica gel beads, [Build It Make It] sought a more permanent way to keep his filament dry. Already familiar with activated alumina beads, he crafted a desiccant cylinder that can be popped into the oven all at once instead of all that tedious mucking about with emptying and refilling plastic capsules.

A length of aluminum intake pipe, some high temperature epoxy, and aluminum mesh are all combined to make a simple, sealed cylinder. During the process, he found that using a syringe filled with the epoxy led to a much more precise application to the aluminum cylinder, so he recommends starting out that way if you make these for yourself.

We suspect something with a less permanent attachment at one end would let you periodically swap out the beads if you wanted to try this hack with the silica beads you already had. Perhaps some kind of threaded pipe fitting? If you want a more active dryer, try making one with a Peltier. If you want to know just how dry your filament is getting, you could also put in a sensor. You might also wonder, do you really need to dry filament at all?

21 thoughts on “Activated Alumina For Desiccating Your Filament

      1. Cheap indicating silica gel can be found in the form of ‘crystal cat litter’. I drilled a bunch of holes in a peanut butter jar, filled it with that litter. It’s used to keep various materials dry. When the blue color changes, toss it and get some fresh. Seems to last quite a while.

  1. I have an Eva-dry E-333 Mini Dehumidifier for $14 (Amazon), plus an airtight tote to store my filament. You can purchase air-tight totes online, they’re not generally available in Target or WalMart.

    The dehumidifier is a big pack of dessicant, it turns green when full, and you plug it in and it will refurbish itself/heat up the dessicant, and you can put it right back in.

    I have two – one for filament, and one for raw copper.

  2. Been using #d printing for 3 years now. Never once have I done anything to my spools of filament. When I change colors I just toss it on the shelf. I have never had any issues.

    1. I have PLA that is almost 10 years old. It still prints fine, never dried it. It did get a bit more brittle after all those years.

      But humidity effect different materials in different ways.

  3. I have doubts that moisture in the filament is really such a big problem.
    In the last 10 years I have printed 50+ rolls (PLA PET PETG) and I have never noticed anything, even with older material. My suspicion is that the real problem is a printing temperature that is too high, possibly due to incorrect measurement or because the air is ventilated directly onto the hotend.

    1. Or your house is low humidity. I’ve had filament print fine, have issues, then I dry it out, problem solved. I now control the humidity in my house and my filament. If I didn’t control humidity it has gone up to 100% lately at times.

  4. If you want to upgrade from silica beads, the easiest next thing is zeolite beads. They’re a bit more available than the alumina, and don’t crack as much as silica. Might get the area a bit dryer than with the silica, too, though I’ve not tested. (What I did with them, unsuccessfully, was try to make a pressure swing adsorbtion concentrator by filling a pipe with them. No luck, unfortunately; not sure if the ones I got were mislabeled or what.) With silica you might get a fair amount of water out just in a microwave, if you have a nonmetallic container; else you need a flame or the oven. I might still like to have a removable threaded end; no need for it to be airtight for this so you could forgo any thread sealant. Still seems like a fair solution!

      1. Oh, I just saw [rockso]’s comment (first comment on this article) which says a microwave oven is useful for drying silica beads.
        I keep a microwave oven, that has a wonky display, in the garage to avoid upsetting SWMBO with non-food experiments.

      2. Oh, I’ve used a microwave with silica – but I was using the kitchen one, so I didn’t run it long enough to know whether there could be problems. I only needed to dry them part of the way, because I was just trying to get water out of my car that was fogging the inside of the windows in the morning, so I got them fairly hot and then took them out and blew air over them. Other times I just used the regular oven, but then I needed a tray and all.

  5. I bought at Micro Center (~$10) a pack of 10 zipper lock plastic bags, large enough to hold a 1Kg spool of filament, with a vacuum valve and a separate suction pump. The purpose is to store used/open filament in an airtight environment.

  6. Printing with Nylon, humidity is a constant battle. Silica gel FTW. It dries well and fast in the microwave but do short bursts and fan it (air flow) in between to move the moisture. If you overdo it, the gel WILL burn

  7. “Frustrated with the consumable nature and fussy handling of silica gel beads, [Build It Make It] sought a more permanent way to keep his filament dry.”

    Huh? I refresh silica gel beads all the time. I put a tray full of silica gel packets in an oven set to around 220 deg. F for thirty minutes or so and the indicator beads go right back to the “dry” blue color. The process is completely reversible. I use the silica gel packets to keep my gun and ammo lock boxes bone dry between trips to the range. I’ve been reusing the same bunch of silica gel packets weekly for almost four years:

    * Dry & Dry 10 Gram [50 Packets] Blue Indicating (Blue to Pink) Silica Gel Packets Desiccant Moisture Absorbers – Rechargeable Silica Packets, Silica Gel, Silica Gel Packs, 4.5 out of 5 stars 191 ratings, $16.99, $3.40/10 Packets.

    https://www.amazon.com/Dry-Premium-Indicating-Silica-Packets/dp/B06X3SP3J6

    Purchased: Thu., 27-Aug-2020 01:50 AM ET, Order: ***-*******-****858, charged to Visa …9826, Delivery: Friday, Aug 28

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