At what RH do I need to worry about humdity?  

RE: At what RH do I need to worry about humdity?

Posted by: @szumi

Winter here in northern michigan.  RH in the house is 24%, a zip lock with silica gel is at 29% after cooking it in the microwave until the indicating beads turned blue.  I think I'm good right now with my filament hanging off my printer.  I had a spool of petg up for a week, didn't see any problems, got a spool of TPU up now to explore flexible printing.

At what RH should I start pulling my filament after printing and put it in a dry box?  In the summer it gets to 60 to 65 RH in my house.

if not used for a longer period of time, I would put each filament roll in a ziplock bag and add silica gel. Then store in a cupboard or in a box.

For shorter interruptions, I leave the filament on the printer. Nylon is particularly hygroscopic and I usually dry it before use. PLA and PETG are less sensitive to this.

RE: At what RH do I need to worry about humdity?

I am in the habit of baking (drying out) the dry-packs in my dryboxes whenever the humidity inside them starts to creep up to the 30% level.

The humidity in the house has been running in the low 20s for the last few weeks, so I haven't even been watching the drybox humidity gauges.

We have not turned on the furnace humidifier yet this year.  When we do I'll start watching things more closely again.

RE: At what RH do I need to worry about humdity?

In my experience It totally depends on the filament, I live on an Island and even though I'm surrounded by water the RH is normally around 35% inside and out most of the year, during the rainy season it can be up to 55%.

I have no issues at all with leaving most PETG, PLA, ASA ,ABS or even TPE's and TPU's out for a week at a time, as mentioned most of the year is good till the rain season, the exception to the TPU's is NinjaTek Armadillo, it acts just like Nylon, very hygroscopic, with fast permeation even in low humidity. Oddly enough the Ninjaflex and Cheetah don't have this issue here.

I do tend to take what I need for my prints off the roll and then re-vacuum seal the rest for long term storage, always leaving a slightly longer then needed vacuum bag so I can open and reseal as necessary several times.

If any of the filaments I leave out for daily use go funny, I throw them in the printdry to restore them, I almost never need the printdry for anything other then Nylon and the Armadillo, I did order my first roll of PC Blend during the Black Friday sale. so I'll see how it fairs when I receive it.

I do store my actively used filaments in ziplock bags, or even better the reusable bags that some filament comes in, with a refreshable desiccant pack, but frankly that's mostly to keep the dust off of them, I have never thought of ziplock bags as air tight, especially after you shove a spool through the opening.

My conclusion is if your filament is stored/kept somewhere in the 30% to 40% +/-  RH range it's going to be OK, with the few acceptations mentioned.

Also know that you can refresh most filaments fairly easily with a food dehydrator of some sort. If your like myself and have several hundred rolls of different filaments then you might want to consider vacuum sealing for longer term reusable storage.