Antifreeze a NoNo?

I have read the “top mods” post of Nedman (how can i PM ppl here?).
He stated that you should never use Antifreeze in the cooling liquid.
Can you tell me why ( in general)?

What is the optimal temperature of the cooling liquid?

I would like to have a 10litre active coolbox (Peltier-element driven) as my
container for the cooling liquid.
It cools air way below 0°C. I estimate -20°C. So i guess it will cool down
the liquid down to that point as well if i would keep it running for a very long time.

Wouldnt be Antifreeze be the most sane thing to add to the distilled water i use?
Or is this Setup overkill (depends on what the optimal temp. for the cooling liquid is)?


that is waay too cold for laser applications. Optimal temp is 15-20°C with no condensation forming on the laser tube and pipes. And short answer is that most antifreeze increase the conductivity of the water and cause issues with performance.

1 Like

We know exactly what conductive coolant causes [shortens LPS life] but we do not know why. More often than not chronic LPS failures have been associated with conductive coolant. Unfortunately we don’t know exactly what is the right range of conductivity… we do know that distilled water treated with algaecide has a good working conductivity.

My over simplistic theory is that the water jacket full of water capacitive-ly shunts to ground some of the current from the LPS. It is not uncommon to stick your hand in a coolant bucket while operating and get a tickle. Since this current is not in the cathodes circuit it does not show up on the meter and the operator does not see that the actual current being drawn from the supply is greater than it should be run at.
So maybe when running the machine at 20 ma maybe 10 ma is being robed (because the coolant is anifreeze) and the LPS is trying to put out 30ma which is above its recommended running current?

This seems fantastic but consider that:

  • The effective area of the jacket exposed to the voltage and the water is pretty big
  • The voltage on the tube is large 20,000 VDC
  • The max current the supply can handle is 30ma, so 10ma is 30% of the supply’s capacity
  • You can easy imagine 100’s of volts drop across the various effective capacitance’s. One user measured 300v across his coolant bucket.

So you could easily imagine a large plate capacitor with 20,000vdc across it coupled to earth ground through all of the coolant loops surface area.

I have not been able to test my theory cause I have not gotten a hold of an old tube yet to set up a proper test environment.


Here is a great write up on coolants;


Hey thanks to all you guys!
I am relaxing right now because standard purified/distilled water will not really become ice when the room temp hits sub 0.
As long as it is germ"free" it can stay liquid far below 0°C.
So i will read the Link provided (Coolants and Additives).

Do you think UV light along the path of the tubes would be a sufficiant germicide?


It’s not just whether it is frozen solid.

As @Domm434 points out, you want to keep the temperature above the dew point.


You can DM people by clicking on their avatar and clicking on “message”.

1 Like

While DMs are available, we very strongly encourage conversation to stay in the open so that everyone benefits. If you want to just mention someone in a public conversation, just type @username and they will be tagged. Like this: @Lasy

Go through the tutorial offered to you by the bot when you signed up and it will teach you all about that in just a couple minutes.


With dew point you mean 0°C i guess?
That would be my next question.
Can i assume that you can safely operate the machine between +1°C to +20°C?
What about the range from +1°C to +15°C?
What is problematic about that range?
I am asking because +15°-+20° is stated as the optimal temp…

And i will keep discussions public unless it gets intimate.

1 Like

I wondered so I should ask… why is condensation a bad thing on/in a laser tube. Do we know why or is it an assumption?

1 Like

I believe it increases the chance of arcing from the tube to the chassis by acting as an intermediary between them. This sis only from what I have read as i dont let mine get that cold to tempt fate :slight_smile:


Hi. I’m new here. I just ordered a K40 after months of deliberation.

A good friend of mine used to be a partner in a business that designed, built, and sold 1200w co2 laser systems. You read that right. Could cut through inches of steel. Says the beam looked like a flaming sword since it ionized all the surrounding gasses and you’d see the resulting corona discharge. The caveat is that at those power levels you need a cover gas, and that the superheated cover gas is actually doing most of the cutting. Compressed argon plasma vaporizing everything in its path - can only imagine.

Says he has a patent on a nozzle that produces laminar flow inside and surrounding the beam. He has advanced degrees in EET and chemistry and is very much retired. He did ask if the K40 market would be interested in a laser head with a laminar flow nozzle though.

Anyway, earlier tonight i told him that i’d read that high-impedance coolant is required but that RV winterizing coolant, not engine coolant, can be used to retard mold growth and prevent freezing at concentrations of like 15-25%.

He said that high-impedance coolant is indeed required and that the RV coolant will be ok for those tasks.

I didn’t ask why not automotive coolant, but i would hazard a guess that the additives in automotive coolant that retard galvanic corrosion in enignes that have a mix of iron, aluminum, and copper/brass/bronze metals probably greatly reduce the impedance.

The biggest issue with adding coolants is nearly all of them dramatically increase the conductivity of the fluid. the preferred medium is pure distilled water(some add a few drops of algeacide) as its inherently low conductivity prevents laser power from energizing your coolant. For a K40 just go with distilled water, and change it every couple months or so.

Coolants have proven, through experience, to cause LPS failures.
I have worked on 100’s of K40 machines that has this problem …
Just don’t do it …:wink:


Yeah i see that the lasergods page mentions that most RV coolants don’t dramatically increase the conductivity but some do.

Since there’s no risk of freezing here - it’ll be inside the house - I’ll probably just add a little algaecide and a little dawn as surfactant.

Oh, @Lasy asked about UV. I don’t know what kind of glass the laser tubes are made of but i sort of presume it is silica. The usual way to use UV-C (100-280nm) light as a biocide for water is to plumb the water through a quartz tube that has a UV-C source next to it, say inside a box lined with reflective foil. I vaguely recall a discussion about how quartz glass is necessary for this because other glasses tend to “solarize” and gradually stop passing the wavelengths that are flaming death on microbes. I keep meaning to build a mini UV sterilizer setup for my cat’s water fountain. Some day.

That might be worth opening as a separate topic with a poll. Use the gear icon at the top of the editing box and choose “Build Poll”

I’ll have to ask him how serious he is about the idea.

1 Like