I have been using dishwasher Salt as a dessicant for years to keep moisture out of wardrobes, cupboards, and most other places in caravans and sheds etc.
It is cheap, can absorb twice its weight of moisture and easy to see its working as it starts to solidify and can buy it in local aldi or lidl for around 79p a kilo.
I’ve not been hobbying for most of the past year due to illness, just starting back on 3d hobby now. Most fillments, mainly pla and some petg where left in the open of cold garage. So need to do a drying spree and some cereal dry boxes for storage.
So I’ll try out the Salt option and some silica beads i have that are still orange.
Would be interested in hearing if anyone else has tried it.
I have never heard of dishwasher salt, I had to Google it. It seems natural (not pellets) water softener salt may work as well.
I am interested to hear if it works. I am curious if there could be some salt transfer to the filament that could damage printer components. A ‘salty’ environment can be corrosive.
Salt diluted in water causes a corrosive liquid to form. But dry salt not do. Given that it will be absorbing moisture, then theoretcslly yes, but i doubt it at the absorbtion levels we would see. Also the salt would be in a bag, so not direct contact with filiment or spool while in the ceareal box.
Also i am not relying on saltto do the major drying, i ensure filiment is dry enough before it goes in cereal box.
The salt us there just to stop moisture building up quickly in the box.
I had never heard of dishwasher salt, asked Google:
Dishwasher salt is a special, coarse-grained sodium chloride used in dishwashers with built-in water softeners to combat hard water, preventing limescale buildup, spots, and streaks on dishes and protecting the machine’s components by removing hardness minerals (calcium and magnesium). While similar to table salt, dishwasher salt’s larger granules prevent clogging the softener reservoir, and it’s crucial for dishwashers in hard water areas, boosting detergent performance for shinier results, with brands like Finish and Miele recommending it.
Also asked: How much moisture can dishwasher salt absorb as a desiccant?
Dishwasher salt (sodium chloride - NaCl) has low to moderate moisture absorption, working best in very humid conditions (above 75% RH) by dissolving in water vapor rather than forming strong hydrates like other desiccants, meaning it can only reduce humidity to around 75% RH, not dry air completely; for serious desiccation, you need strong desiccants like calcium chloride or silica gel, which absorb much more water (e.g., 150-300% of their weight).
How Dishwasher Salt Works (and Doesn’t)
Sorption vs. Absorption: Salt acts as a desiccant by dissolving in water vapor (sorption) to form a saturated solution, rather than absorbing water into its crystal structure (absorption) like silica gel.
Limited RH Reduction: A saturated salt solution in dry air will only lower the Relative Humidity (RH) to about 75% at room temperature, making it ineffective for very dry conditions.
Best in High Humidity: Its ability to absorb is low but becomes noticeable in very humid environments (above 75% RH).
Comparison to Other Desiccants
Calcium Chloride (CaCl₂): High capacity, absorbing 150-300% of its weight in moisture, but becomes liquid.
Silica Gel: Moderate capacity (25-40% of its weight), effective in a wider range of conditions but less powerful than CaCl₂.
In Summary
While salt can technically absorb moisture, it’s a poor desiccant for most needs, only effective in extremely humid spots and unable to dry air significantly.
I usually recharge my desiccant when RH in the storage containers rises to 20%.
For filament storage, salt would be a totally ineffective desiccant.
Great information and explanations, thanks.
So will calcium chloride (deicing salt?) work better, as thats also very cheap.
Used as a dessicant would it still liquify?
While similar to table salt, dishwasher salt’s larger granules
“Dishwasher Salt” sounds like rock salt to me. I buy it in 50Lb bags for the winter season, spread it on my walkways when it gets icy.
Worth noting, whatever sits in the garage over the summer months ends up solid as a rock because it absorbs moisture that welds the salt crystals back together. I have these puck shaped salt tablets to throw on to the roof to melt ice dams, they come in a plastic bucket. I left a bucket in a corner of the garage for a couple of years, when I checked it out the bucket was full of water and the salt pucks were gone.
Salt diluted in water causes a corrosive liquid to form.
Note that salt dissolved in water doesn’t normally generate any corrosives. NaCl is a neutral salt. It’s formed from a strong acid (HCl) and base (NaOH). If it breaks down, it just breaks down in to Na and Cl ions. If they could crack a water molecule, they’d have what they needed to turn back in to HCl and NaOH. But They don’t react with the water (as “conjugates” of a strong acid/base pair, they are stable) and the solution’s pH stays neutral.
Salt water will attack some things including metals like Aluminum and Copper. But it’s not an “attack” by a strong acid or base. It’s a corrosion process.