Can this handle filament soaked in water for 24 hours? GratKit Firefly Dryer Review


Positive Points:

  • Effective Drying Performance: The Gratkit Firefly dryer demonstrates excellent performance in drying various filaments, including PLA and PETG, effectively reducing moisture content over time.
  • User-Friendly Interface: The dryer features a user-friendly control panel with 8 preset drying profiles, 2 custom profiles, and manual temperature and time controls, making it easy to operate.
  • Additional Features: Innovative features such as tilt protection, remote app control via the Tuya Smart App, and adjustable RGB LEDs enhance the overall user experience and functionality of the dryer.

Negative Points:

  • Slight Spool Holder Inconvenience: Using the Firefly as a spool holder while printing can be slightly inconvenient due to needing to feed the filament through the hole. Meaning you cannot remove the role without unloading from the printer.
  • Premium Price: While the Firefly dryer includes innovative features not found in many other dryers, its price of $79.99 USD may be considered on the more expensive side for a single-spool dryer, especially for users seeking a more budget-friendly option.

See details about the GratKit Firefly dryer here (affiliate links):
CA :
DE :
IT :
ES :
UK :

GratKit’s website:

My Dry Storage:
46qt Storage bin:
Eva-Dry Dehumidifier:

Videos Referenced:
This is the best way to store 3D Printer FIlament:
How wet is new 3D Printer FIlament?
Creality CR-10 SE review:
Increase 3D Print quality by drying filament:

Video Transcript:

Hey everyone, and welcome back to Hoffman Engineering. Before we start, let me just get this filament soaking in water really quick. Perfect. We are back with more filament moisture experiments and a new dryer review! In my previous videos in this series, I’ve built my favorite simple dry-storage box and explored how long it takes to dry out new filament with normal desiccant. Last video we looked at filament dryers and explored drying times with PLA. In this video, I want to look at other filaments like PETG, and see if this Firefly Filament Dryer from Gratkit can handle a roll of filament soaked in water for 24 hours. 


Before we begin, this Firefly filament dryer was sent to me for review by Gratkit. Like with all of my reviews, they aren’t paying me for this review, and everything I say is my own honest opinion after using this dryer for the last couple months. My videos are supported by my patreons, as well as affiliate links in the description, so you can help support my channel at no additional cost to you. Lets get into it.


The Gratkit Firefly is a single roll filament dryer. The dryer is designed to circulate warm air up and around a roll of filament, driving away moisture. Dry filament will increase 3D print quality, so having dry filament is important. The body of the Firefly is rather compact, with a size of 254 by 261 by 102 millimeters, and weighs only 760 grams. It has a black translucent lid, with a black plastic body. The control panel is attached to the lid, and lets you select one of 8 preset drying profiles, 2 custom profiles, or manually control the temperature and time. The panel also shows the current temperature inside of the dryer, the relative humidity percentage, and the fan RPM. On the back of the panel are 4 adjustable RGB LEDs, which gives a pleasant glow to the inside of the dryer. On the back we can see 2 holes which you can pass filament through, if you wanted to print with the filament while drying.

The Firefly can reach temperatures of up to 70 degree celsius, which is perfect for nylon and polycarbonate filament. It has two temperature sensors, at the bottom and the top, and it will automatically adjust heater power and fan speeds to ensure the filament isn’t overheated

The lid opens up to reveal space inside for 1kg, 500 gram, or 250 gram spools. The spool can be supported by the central holder, or by the pair of bearing rollers at the bottom of the dryer. I found the center holder perfectly sized, it fit every spool size that I had, and you could always 3D print a new one if you needed a custom size.

The heater is attached to the center of the bottom metal plate. Next to the heater is a fan, which blows air past the heater, which circulates up the back of the dryer and over the top of the spool. You can see the residue from some of my testing on the bottom plate, but it was perfectly clean when it first arrived.


Here are the settings for the 8 built-in profiles. They are a good starting point, but I found the PLA profile to be both too short and too low temperature, at 40 degrees celsius for 4 hours. Most recommendations for PLA are to dry at 50 degrees celsius for around 8 hours, so 40 degrees is very cautious. I had no problems with the Firefly running at 50 celsius for PLA in a few of my tests. The other profiles seem pretty good, although maybe a little short, but you can always manually add time, or set the time to zero-zero to let it dry indefinitely.

The Firefly has an important safety feature that I haven’t seen in many other dryers, and that is tilt protection. It detects if the dryer has been knocked over, and it will automatically turn off the heater. 

Finally, the Firefly can be remotely controlled via the Tuya Smart App. The dryer can connect to wifi, and you can use the app to control the dryer. All features are adjustable via the app, you can select any of the preset profiles, adjust temperature or timing, and even adjust the LED colors or patterns. I noticed that the app can be a little slow to react, it takes a few seconds between clicking an option and the dryer  responding. But it works well enough, and its useful to see temperature and humidity in the app. The Tuya app is a smart-home app, with connections to google home and apple homekit, but I did not fully explore if the Firefly can be controlled via smart-home integrations.


Lets run some experiments. In my last video, someone recommended testing a completely water-logged spool to see what happens, so thats why I’ve been soaking this spool for the last 24 hours. You know, a completely standard thing that has happened to every 3D printing enthusiast atleast once, right? While that is soaking, lets open some brand-new filament and get them drying in the Firefly dryer, using their preset profiles.

First up, this roll of white PLA from Two Trees. We can see that it started at a weight of 1174 grams, and over 12 hours it gradually lost 4 grams where it seemed to settle out.

This roll of Creality’s Hyper PLA was even more dramatic. Starting at a weight of 1186 grams, it took almost 24 hours to lose 8 grams of weight. The Firefly did an excellent job of drying out this filament. 

Now lets look at PETG. Unfortunately I don’t have detailed hourly logs, instead I just have start and end weights. This Overature Black PETG started at 1162 grams, and lost 4 grams total over 24 hours. The White PETG lost 6 grams total, over 12 hours of drying.

[Water Soaked]

Time to take out the water soaked filament after 24 hours of soaking. First I shook off as much of the water as I could. The weight was 945 grams, which is 84 grams higher than the 861 grams it originally weighed. And then I put it in the firefly and let it run for the next few days. The dryer obviously was not designed for extremely wet filament. It immediately started to condense on the inside, with vapors even making its way into the control panel. No lasting damage was done to the panel though. It also started to drip down directly onto the metal of the heater. All the minerals in my tap water left a nice spot on the heater. But here are the results. It took about 96 hours to dry, even losing 3 extra grams of water from its starting weight. But it looks like the Firefly was able to dry out about 1 gram per hour at these extreme conditions.


Lets wrap up this review. The Firefly dryer from Gratkit is a very capable single-spool dryer. The 8 preset profiles makes it easy to switch between recommendations for different materials, although I’d probably use one of the DIY profiles for PLA with a slightly higher temperature. I found it does an excellent job at drying filament though, and didn’t have any concerns about overheating the spools. The compact size is nice when space is an issue. The RGB LEDs and remote app control are kind of gimmicky features, but they are features not found in many other dryers. On the negatives, using the Firefly as a spool holder while printing is a little inconvenient, because you have to feed the filament through the holes, so you can’t remove a spool without first unloading it from your printer.

The Firefly dryer retails for $79.99 USD as of the time of this recording. That is on the more expensive side when it comes to single-spool dryers. The Firefly does include features that I haven’t seen on other dryers though, so you might find those features like the smart-app control and tilt-protection worth the more premium price.

So thank you all for watching my review of the Gratkit Firefly single-spool filament dryer. If you have any questions, comments, or suggestions for futures tests, please let me know about them in the comments below. And if you are interested in dry filament, be sure to check out my other videos about dry storage and filament moisture. These are exciting times in 3D printing, for sure. So thank you all for watching, and I’ll see you all next time.

Post Tagged with , ,

Leave a Reply

Your email address will not be published. Required fields are marked *