Lowest safe temperature for storage of glowforge (coolant, does it expand.. freezing point)

Hi all

My glowforge is in a garage. In Chicago. And it’s now freezing outside.

My garage is warm because of the house. Unless the big door is up, then it gets cold

So. I know these are shipping in the freezing cold.

I also have not seen mention of a lowest temperature to subject your glowforge to!!

What is the official word?

I imagine that nothing can be damaged by cold except the parts touching the coolant (unless this coolant doesn’t expand??) which would be the glass laser tube.

I also imagine that moving parts may have an operating temperature to ensure proper lubricant

I also imagine that warming the tube fast from low enough temperature, could cause it to crack.

Interested in this as well.

I vaguely recall 50 F being the minimum operating temperature.

My 'forge is in the basement, so gets pretty chilly but not outside levels of cold.

I imagine that nothing can be damaged by cold except the parts touching the coolant (unless this coolant doesn’t expand??) which would be the glass laser tube.

If there’s damage to be done by cold conditions my bet is on it being from condensation forming while the unit is running or thermal shock on the glass tube, both of which can be mitigated by slowly restoring the unit to safe operating temperature (50?) before starting to run.

They also recommend removing the Glowforge from the external venting to prevent inflow of exterior conditions directly to the machine – though the way mine is set up, this is a bit of a pain.

I tend to leave my lid a bit open instead, to allow interior air to circulate in. My vent is louvered, so there isn’t going to be much backflow, but it’s been below freezing lately, so better safe than sorry.

EDIT: Don’t want this:

I have louvers and a manual blast gate in line with the exhaust, it is only open when the machine is running, seems to work so far.


Hey, how well does that blast gate seal? I thought about installing on but was worried about gaps and smoke.

i have a similar blast gate in mine.

just don’t be foolish and forget to open it, like i did a couple of times, smoke will start pouring out of the crevices. :slight_smile:



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The GLOWFORGE USER MANUAL states the minimum temperature where the GF can be kept is 40 degrees


The minimum OPERATING temperature for the GF as stated in the manual is 60 degrees


From the Manual…

Temperatures below 40 degrees Fahrenheit (5 Celsius) or over 120 degrees Fahrenheit (48 Celsius)
Extreme humidity conditions (below 10% or more than 75%)
If venting outdoors, ensure that changing conditions do not cause extreme
temperatures or humidity to enter the Glowforge unit through the exhaust hose.
Disconnect the hose from the outside air when the Glowforge is not in use.

Another forum link.


I used the provided GF hose clips on both the GF exhaust outlet and the inlet of the blast gate . The blast gate is Gorilla-glued to a plywood insert that goes in my basement window while I’m running, and the “male” Louver unit is Gorilla-glued to the “female” socket of the blast gate. No leaks to speak of.

I’ve never done that before…

Thinking of automating it with a current sensor and a servo.

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So I want to separate the humidity concerns from the temperature concerns

Within temperature, I then want to sub-separate the concern of storage/shipping of the unit, from the temperature while operating

  • Humidity

    • precautions like venting, exposure to humidity from outside
    • min/max humidity in the general air
  • Temperature

    • storage / shipping of the unit
    • operating the unit

Some of the guidelines are ambiguous whether they exist because of humidity or because of some temperature concern.

My main concern is of storage and temperature

I put an electric blanket over the top of my GF when things got chilly here last week, in order to keep it above the 40 degrees listed in the manual.


I suspect the low point for temperature will be defined by the coolant. As long as the changes are slow and within proper humidity

But I’d like some official word on what the coolant is made out of ( or brand, if applicable), so that I can better understand the actual minimum

They give a minimum recommended storage temp?

There should be a Material Safety Data Sheet for the coolant, and being as we already had one person’s tube crack and the coolant escape, it would be reasonable to request GF have the MSDS available to the end user.


It’s in the user manual. Must be between 40 degrees and 120.

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The minimum stated temp of 40deg F is problematic. Aren’t they shipping during the winter? So… it’s going to be less than 40… I’d like to know what that is.

If it really is 40, then that implies water. If that’s true, there will be problems shipping in the freezing weather. Unless they’re shipping with both laser & coolant tubes completely empty, with room to expand in the tank…

Water as a coolant just seems like an engineering mistake given the diverse locales around the globe, and unknowable shipping temperatures :slight_smile:

Only if hazardous and Dan has stated normal clean up and disposal if required.