What effect does moisture have.



  • It has been several months since using the printer, due to massif failure, all this time the filament has sat with the printer completely exposed to the enviroment.

    I know that PLA can absorb moisture from humidity etc. what I don't know is what effect it will have on the prints.

    Since rebuilding the printer, I am getting some horrible results, wondering if this is due to bad configuration or bad filament.

    Can anyone tell me what to expect if the filament has absorbed moisture

    Thank you


  • Moderator

    You are right that PLA absorbs moisture from the atmosphere. This is called hygroscopy. All plastics are hygroscopic to some degree, although usually the effect is negligible in ABS and PLA. Other materials, like Nylon, can actually carry so much water that they bubble and steam while printing. To prevent this, they must be stored in a sealed container with dessiccant.

    In our experience, old PLA gets more brittle as it ages. I cannot say whether this is actually due to hygroscopy, or due to the breakdown of the polymers from exposure to UV light. In either case, this happens over the course of many months or years. Eventually it gets so brittle that it will not even feed into the printer without snapping.

    You can try to dry your filament by putting it in an oven for a couple hours on very low heat. We use a vacuum oven for this, but a conventional oven is better than nothing. Just make sure to keep it below the glass transition temperature (60 C or 140 F).



  • Thanks that is very good to know, but what I was after was, what will it do to the print quality.This may help me diagnose my failures, if it is the filament I can toss it out, but unless I know, I could go on for ever trying to unnecessarily making adjustment.to the printer.


  • Moderator

    The print quality is not really affected except in extreme cases where there is bubbling and a hissing or popping sound, due to the water being boiled off. The bubbles will be large and easily visible in filament that is extruded freely in the air. It will make the print very porous and rough.



  • Thank you, I don't see any bubbles or here any noises, but that's understandable I am half deaf.😢



  • So what I'm hearing is that drying PLA may or may not have any affect on its brittleness? My boss got a "deal" some printers that were returned. As far as I can tell, the machines are fine, but the filament has been open for a long time. There seem to be localized sections of brittle filament (3 to 6 inches long each) that keeps breaking and jamming in the tube to the extruder. The material on either side, however, is nice and flexible. If the brittleness is due to moisture absorption, shouldn't the brittleness be relatively uniform? Obviously I have no idea if the original purchaser stored the spools in the sun or not, but I'm having the same issue with six spools from three different machines. We're already working on a desiccant chamber for storage, but should I just start fresh with new filament? I'm not really looking forward to telling my boss that we need to buy new spools at $50.00 a pop.



  • When I had a spool that became brittle, I attacked it with a hair drier, seemed to make a difference, so the oven may help as well. Anything to keep the boss happy.😆


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