Filament Drying
How to dry filament
A dryer is the easy answer. An oven works with care. The print bed does not. Here is the detail on each.
By Michael W. · Published October 5, 2026
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The four methods, ranked
- A filament dryer. Controlled temperature, designed for the job, and the only method that is also convenient. Right answer if you print hygroscopic material regularly.
- A food dehydrator. Genuinely good — accurate low-temperature control and good airflow. Many will not fit a full spool without modification.
- A kitchen oven. Works with real care. The risk is the thermostat, which in domestic ovens is often out by a wide margin, and overshooting fuses the spool into a solid block.
- The print bed. Does not work properly. It heats the spool from one side with no airflow and no enclosure, so moisture is driven around rather than out.
Temperature by material
| Material | Class | Served by a 70 C unit? |
|---|---|---|
| PLA | Low — the most heat-sensitive common filament | Yes, at the low end of the range |
| PETG | Low to moderate | Yes |
| TPU | Low to moderate | Yes |
| ABS / ASA | Moderate | Marginally — a higher-temperature unit is better |
| Nylon / PA | High | No |
| PA-CF / PA6-CF / PA12-CF | High | No |
| Polycarbonate | High | No |
Use your filament manufacturer's stated drying temperature, which is on the spool or the datasheet. This page gives classes rather than exact numbers deliberately: the correct figure varies between brands of nominally the same material, and the consequence of being wrong at the top end is a ruined spool.
The oven method, with the warnings that matter
It works and it has ruined a lot of spools. Three rules:
- Do not trust the dial. Domestic oven thermostats are frequently out by a wide margin, and many have no useful control at the low end of their range at all. Put an independent oven thermometer inside and go by that.
- Use convection if you have it. A fan oven moves air, which is what carries moisture away, and it holds a more even temperature than radiant heat. A conventional oven has hot spots that can deform the side of a spool facing the element.
- Stay well below the glass transition temperature. Not just below — well below. The margin is your protection against thermostat error.
The failure mode is memorable: a spool fused into a single solid block of plastic, with the windings welded to each other. It is not recoverable.
Why the print bed does not work
It gets suggested constantly and it is not a method. A spool sitting on a heated bed is being warmed from one side, in open air, with nothing to carry moisture away and nothing to stop ambient humidity returning to the far side.
What you get is a warm spool rather than a dry one, and on an enclosed machine with the door shut you may also deform the part of the spool in contact with the bed. If you have no dryer, an oven or a dehydrator is the improvisation that actually works.
How long, and how to tell it worked
I am not going to give you hours, because the honest answer depends on the material, the starting moisture content, the spool mass, the airflow and the temperature — and measuring it properly needs equipment this site does not have.
What is reliable is the test: print the same part again. If popping stops, stringing drops and the surface improves, the filament was wet and now is not. If nothing changes, moisture was not your problem and you should stop drying and go to print quality triage.
A hygrometer inside a sealed box gives you the storage half as a number. For the drying half, the print is the instrument.
Then store it sealed
This is the step that gets skipped and it is half the job. A dried spool returned to an open shelf in a humid room undoes the work within days for nylon, weeks for PETG.
Airtight container plus rechargeable desiccant plus a cheap humidity indicator. The indicator matters because desiccant saturates silently, and a sealed box with exhausted desiccant is just a box. Storage options.
Where to go next
Confirm moisture is the problem before buying anything. Dryer picks by temperature and capacity. Whether you need one.
What to buy
Stock photograph of this product class, not of this specific unit.
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1. Easiest correct method
SUNLU FilaDryer S2
A cited 35-70 C range, controlled, quiet enough overnight - which is the whole job for PLA, PETG and TPU.
The reason to own a dryer rather than improvise is control. An oven thermostat can be out by a wide margin, and the gap between drying and deforming a spool is not large.
A cited 35-70 C range covers PLA, PETG and TPU, which is most hobby printing, and it is noted as quiet enough to run overnight.
What it gets right
- 35-70 C covers PLA, PETG and TPU, which is most of what actually goes wet in a hobby workshop
- Quiet enough to run overnight in a room you sleep in
- The cheapest entry point that is still a real dryer rather than a warm box
What it does not
- 70 C ceiling means nylon, PC and PA-CF are out of range
- One spool at a time, which does not fit a four-color job
- No printing from the unit, so a dried spool starts re-absorbing the moment it comes out
| Temperature range (cited) | 35-70 C |
|---|---|
| Capacity | One spool |
| Diameters | Supports all common filament diameters |
| Noted | Quiet enough for overnight drying |
Stock photograph of this product class, not of this specific unit.
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2. For nylon and polycarbonate
SUNLU E2 FilaDryer
A cited 35-110 C with a 500 W PTC heater, which is the class those materials require.
Cited at 35-110 C with a 500 W PTC heater, named for PA6-CF, PA12-CF, PC, ABS and ASA. If your material list includes nylon or polycarbonate, no amount of time at 70 C substitutes for this.
It also anneals, which is a second genuine use. Annealing shrinks and distorts parts, so treat it as a technique to learn rather than a feature to use casually.
What it gets right
- 110 C is the first number on this page that is genuinely enough for nylon and PC
- A 500 W PTC heater gets to temperature fast instead of creeping there over an hour
- Doubles as an annealing oven, which is a second real use rather than a marketing bullet
What it does not
- Overkill and over-priced if PLA and PETG are all you print
- A 500 W heater is not a quiet, low-draw appliance
- Annealing shrinks and distorts parts — it is a technique to learn, not a button to press
| Temperature range (cited) | 35-110 C |
|---|---|
| Heater (cited) | 500 W PTC |
| Second function | Annealing as well as drying |
| Materials cited | PA6-CF, PA12-CF, PC, ABS, ASA |
Stock photograph of this product class, not of this specific unit.
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3. For keeping it dry afterwards
Polymaker PolyDryer
Sealed storage at a cited 10-20% RH, which is the half of the job drying does not do.
Drying is an action; staying dry is a condition. A spool that goes back onto an open shelf after drying has bought you days or weeks depending on material and room.
Passive sealed storage plus active drying, cited as reaching 10-20% RH, bought one box at a time. Cheap airtight tubs with rechargeable desiccant do the storage half for less, less neatly.
What it gets right
- The modular box system means every spool lives sealed, which prevents the problem instead of fixing it
- A cited 10-20% RH is the number that matters, and it is a good one
- Cheap to start with one box and add more, instead of one large purchase
What it does not
- Buying enough boxes for a full filament shelf adds up past the price of a four-spool dryer
- Standard-temperature drying — not an engineering-filament answer
- Per-box storage takes more total shelf area than a stacked rack
| Approach (cited) | Passive sealed storage plus active drying |
|---|---|
| Humidity reached (cited) | 10-20% RH |
| Entry point (cited) | From a per-box price, boxes bought individually |
Questions people actually ask
How do I dry filament?
A filament dryer is the easy and correct answer - controlled temperature, designed for the job. A food dehydrator works well if a spool fits. A kitchen oven works with care, using an independent thermometer and a convection setting. The print bed does not work: it warms one side of the spool in open air with nothing carrying moisture away.
Can I dry filament in the oven?
Yes, with three precautions. Do not trust the dial - domestic thermostats are often out by a wide margin, so use an independent oven thermometer. Use convection rather than radiant heat if you have it. And stay well below the material's glass transition temperature, because overshooting fuses the spool into a solid block.
Can I dry filament on the print bed?
Not effectively. The spool is heated from one side, in open air, with no airflow to carry moisture away and nothing stopping ambient humidity returning to the far side. You get a warm spool rather than a dry one, and you may deform the part touching the bed.
How long does it take to dry filament?
It depends on the material, how wet it was, the spool mass, the airflow and the temperature - and we publish no figure because measuring it properly needs equipment this site does not have. The reliable test is to print the same part again: if popping stops and stringing drops, it worked.
What temperature should I dry PLA at?
At the low end of a dryer's range, and specifically at the temperature your filament manufacturer states - PLA is the most heat-sensitive common filament and the margin between drying and deforming is smaller than for other materials. Exact figures vary between brands of nominally the same material.
Do I need to store filament sealed after drying?
Yes, and skipping it wastes the drying. A dried spool returned to an open shelf reabsorbs moisture within days for nylon and weeks for PETG. Use an airtight container with rechargeable desiccant and a humidity indicator, because desiccant saturates silently.
Sources
Read this next
- How to tell if your filament is wetThe three near-conclusive signs of wet filament, the ambiguous ones, and the free test that settles it in one print.
- The best filament dryers in 2026Dryer picks split by temperature range and capacity, because a 70 C unit and a 110 C unit are different products for different materials.
- Is a filament dryer worth it?Who a dryer genuinely pays for, who should buy sealed storage instead, and the free test that settles it before you spend.
- Drying filament in an AMSWhich AMS units actually dry, what that gets you over a standalone dryer, and the material ceiling that still applies.
- Filament dryer boxesHow per-spool sealed boxes differ from four-spool dryers, the humidity figure that matters, and where the modular approach stops scaling.