PLA breaking question

[Tim]

Try drying it out with dessicant for a couple of weeks.

I thought that dessicant was only good for keeping filament dry if it was already dry. . . that you can't draw moisture out of filament, just keep it dry enough that it won't absorb it in the first place. And that to get filament dry, you have to bake it out (which is tricky with PLA, since it goes soft at such a low temperature). And also that there was a recent thread on this forum about debunking the whole rice-as-a-dessicant thing.

[Tim]

the new v3b is a champ and looks better then the old one, just don't like how I need to be 10 degrees hotter for the same material.

I'm half a year late responding to this, but I was reading back through the thread and thought it worth mentioning that it's not that the heater is 10 degrees hotter, it's that the thermistor is 10 degrees hotter just because of the way heat is distributed through the heat core and where the thermistor is located.

[Jules]

And also that there was a recent thread on this forum about debunking the whole rice-as-a-dessicant thing.

Not trying to debunk ed's marvelous experiment - I'm quite sure that the dessicant crystals kept the air drier inside the safe that he had everything locked up in.

But.....having said that........

I used 1 lb. heavy foodsaver plastic bags with a ton of tiny holes poked in them, filled with dry rice. Rice does absorb some moisture. I've used it to dry out electronics that got wet. It absorbs water out of cracks that are too small to shake the water out of. It can be used in a home-made heating pad, because it can be microwaved to warm it, and the moisture in the rice keeps it from bursting into flame. But if you microwave it for too long, it will catch fire, indicating that the moisture gets cooked out of the rice. (Thirty seconds max nuke limit at a time with a heating pad. )

The spool of filament that i stored in the sealed bucket, when i put it in, was brittle and could be snapped easily with minimal pressure. After two weeks of being sealed in the tub with the rice, (without me opening it and letting in more humidity), that same spool of filament was flexible again. It is still flexible now, even though i had to take the rice out because of the bug issue. But it is less flexible than it was when the rice was in there.

In addition, when i bought filament back in February, i bought one of every PLA color i fancied at the time - and that came out to about 15 rolls. They were stored in four buckets with Gamma Seal lids, and a bag of rice. That was ten months ago, and as long as i left them in the buckets when i was not using them, they worked just like they did when i bought them. If i forgot and left a spool out for several days - it got a little stiff sometimes. Putting it back in the bucket with the rice seemed to dry it out again. (Anyway it would get more flexible.)

Last night, i whipped up a few quick sock bags of "indicating silica beads", and i've now put those into the buckets. (After i took the bags of rice out, I only had a few little tiny dessicant packs that came with the spools tucked in there - definitely not enough to keep the humidity down.) But I'm looking forward to seeing if the beads keep the filament as dry as the rice did. (They're actually flower drying beads, which are supposed to pull moisture out of objects.) So we'll see if they work.

If it's better, i'll definitely post it here, with a link to the source for the beads. (They run about $26 for a five pound can.) If it's not, I'll buy more rice, bake it, nuke it, freeze it, (make damned sure that nothing hatches out of it ), and then go back to using the bags of rice to dry the filament out, because even though it wasn't supposed to work terribly well, in my experience.....it did.

Whatever works.

The good news is those Gamma Seal lids DO keep air out of the buckets. (The two I hadn't gone into in a while had dead bugs in the rice bags. Much less traumatic, overall.)

This has quite put me off of rice for a while too. (Sigh.)

[Tim]

I'd never heard of Gamma Seal lids before, but that looks like what's on my air-tight pet food containers that I use to store my filament in. I have been using those with a can of silica beads in each one for about two years now, and I have a humidity sensor in one of them that typically reads 11 to 12 percent humidity. They work really well. The only problem with them is that the containers are tall but the lids are only just big enough to get a spool of filament through, so it's a pain if the spool of filament I'm looking for is on the bottom of the pile.

[Jules]

Excellent! I'm really hoping the silica beads work - much less drama.
And i totally agree on the inconvenience of having to dig the roll you need out of the bottom of the bucket - it's always at the bottom of the bucket!

I finally had to put rather large labels on my buckets to keep from having to open all of them in order to find the color i needed too. (No one tells you these things when you go crazy with the buying spree.)

[Quark]

These are some interesting ideas I've yet to make use of in my collection of filament. It's pretty ironic though that when PLA absorbs moisture, it becomes brittle. Intuition would indicate that it would become softer, therefore more flexible, take for instant dried pasta noodles and when they get soaked with water.

[ednisley]

using the bags of rice to dry the filament out

If you weigh the rice bags going in and coming out, you can tell whether they're doing anything: if they weigh the same, then they're not adsorbing or releasing water vapor. Now, maybe they're gaining or losing bugs, but that's an entirely different matter...

A useful chart for some desiccants:
http://softsolder.com/2014/02/27/desicc ... ity-chart/



Silica gel will hold 25% of its dry weight in water vapor at 45 %RH: a 500 g bag will gain 125 g. The weight really does correlate with the ambient humidity, as I found out with a straightforward experiment:
http://softsolder.com/2013/09/01/monthl ... quilibria/

Those little bitty bags can absorb the incidental water from an electronic doodad tightly sealed inside a bag, but they're no good for bulk dehumidification: there's not enough silica gel to matter.

I'm still surprised that a bag of beads can hold five ounces of water!

The trick to dehumidifying a space is to have a sealed space, which is why those buckets work so well and labeled buckets will work even better. A few humidity monitoring strips will tell you when to regenerate the desiccant; search eBay or Amazon for "humidity indicator strip".

[Jules]

.....If you weigh the rice bags going in and coming out, you can tell whether they're doing anything: if they weigh the same, then they're not adsorbing or releasing water vapor. Now, maybe they're gaining or losing bugs, but that's an entirely different matter...

The trick to dehumidifying a space is to have a sealed space, which is why those buckets work so well and labeled buckets will work even better. A few humidity monitoring strips will tell you when to regenerate the desiccant; search eBay or Amazon for "humidity indicator strip".

Yeah, that would have answered the question.......if i had thought to weigh the bags before i put them in the buckets, when the rice was dry.
(Then again, maybe not....'cause i sure as hell wasn't going to weigh a bag full of bugs on my kitchen counter. )

I'm afraid your experiments will just have to continue to stand as the definitive answer. I'm going to use the silicagel beads now for a while and see how they do. (I'm hoping they will do as well, or better, than the rice.)

Don't need a humidity monitoring strip for these particular beads - they change color as they get saturated. (SorbentSystems). They go from bright blue to light pink when they're full. I left a batch sitting out for the last day, and they're quite pink now - this afternoon, I'll try to refresh them. I'll nuke a third, bake a third and dehydrate a third to see which method works best. (The need to refresh them is one of the reasons i started with the rice and not the silicagel. Around here, it's going to be a fairly constant process, and i'm not sure the indicator color is going to hold up terribly well.)