50% room humidity.

40% when it's hot and sunny, 60% when it's cold and rainy.

I just dry the filament before printing in a filament dryer. Prints fine.

I found more variety in print success and quality when printing filament from different manufacturers then from my varying room humidity. Cheap noname filament often printed like garbage, no matter it's dryness.

The humidity here varies between 3% and 100%.

Things change from PLA being regenerated by being left open to it not lasting for two weeks before it needs drying.

Unless you live somewhere where it's always close to that low in my interval, I do strongly recommend a drybox to anybody wondering if they need one. At 60% humidity, PLA already visibly degrades way faster than you will use in a hobby.

Also, in my experience, filament driers only help with close to dry filaments. The temperature you would need to really dry them is larger than the glass point of most plastics. Microwaves work better (I guess because they heat the water in an uneven way) but it's still hard to regenerate very moist filaments.

@marcos @matlag according to my sources actually you can use PCTG & ASA which are less resistant to moisture in terms of #3dprinting thermoplastic filament I recommend PCTG because it’s in the same family as PETG yet x20 durable

Except winter when heater is on, it's nearly always over 50-60% (and up to 75). I almost never dry my filament, but i work most of time with one open spool at a time. Once opened, my spool last between few days to couple of weeks. With high humidity (65 and over) i usually start to get strings after about a week. Never had strings with 45% humidity except spool that arrived already humid

less resistant

You mean "less vulnerable" here?

I don't think we can move most people out of PLA. It's cheap and available everywhere. But I do agree it's worth pointing that some plastics do not have this problem.

Summer humidity averages 15%RH and winter humidity about 40-60%RH outside. Generally my indoor humidity runs between 30-40% @72F but I don't do anything special to control it.

I store almost all my PLA and ABS in open racks and rarely have a quality issue (Bambu, Kingroon, and Sunlu brands).
My engineering filaments (PC, PET, ASA, and especially TPU) I will dry before use in an AMS-HT and keep stored in sealed containers with dessicant just as a housekeeping necessity. Sometimes I leave them out and it's fine, but they are $ enough that I take care of them to avoid scrapped prints.

If you can't get RH lower than 35% after 48 hours you need to renew or exchange your dessicant. Drying works by heating air until it's RH is extremely low which causes water to migrate out of the plastic into the air via vapor partial pressure, then it gets absorbed by the dessicant to be removed from the system. OR, some dryboxes (ams-ht) continuously exchange air from the outside, which is energy intensive but provides a continuous supply of hot, dry air to remove water from the system.

Dessicant can only achieve an RH equal to its own saturation, which increases with exposure time, so starting with very dry dessicant is a necessity.

Air exchange is less effective in very humid climates, since your heated RH% will be higher, so sealed drybox + dessicant is usually preferred there.

If you aren't actually removing the water with dessicant or air exchange, it will just stay in your drybox and return to the same RH you started at once it cools down.

@marcos the other way is to have enough dehumidifier capacity

I have a spool of PLA that's been sitting out for a year in 30-80% humidity and it printed up just fine, I didn't even dust it off.

Too damn high

25%. My dehumidifier doesn't go lower than that.

Right now, around 50% RH indoors. I leave my spools of PLA on the printer for months or even years, and I've never had any humidity issues. If I were to speculate, my guess would be differences in additives being the main reason that only some people need to dry their PLA filament.

I'm of the general opinion that the hullabaloo about drying filament is largely not warranted in most cases. PLA is just not very hygroscopic and can sit out for months without any issues. Even PETG I don't have any issues with it sitting out. The room I print in sits at about 50% humidity most of the time.

I keep most of my filaments in a box with dessicant that I bake maybe once a year, but I'm not convinced it is really doing much. The only reason I have a drier is that I started printing occasionally with materials that are much more hygroscopic (e.g. TPU).

I have about 50% humidity and don't usually dry my filament and I start to have issues with the outer layer of the spool snapping repeatedly when feeding after a year or two of sitting out. I used to have a dryer for cases like this but it got left behind in a move so I currently try to only use my new spools until I can get another one because I don't trust using the oven and using the heat bed is really slow.

Outside, it usually sits around 65-70% humidity, over 80% during the summer. Hong Kong is like that unfortunately. Dunno about the room my printer sits in though, I don't have a hydrometer in there, but I imagine it's a little bit lower (maybe 60%? 70% in warmer months?). I don't dry my PLA though and I've mostly had good printing experiences.

I live in a dry climate. I don't bother with PLA, but I dry PETG. I printed some stuff from a roll of PETG that had been open longer than a year, and looking closely at the melted plastic coming out of the nozzle, there was noticeable bubbles and stringing during printing. Once dried, all went away. People who claim you don't need to dry some filaments must not care much about quality.

@marcos actually the Resin codes are the most popular because of mass production

@marcos i do not think #vulnerable is the right world to description for thermoplastic #3dprinting filament each has its upper and lower (hands)