[MJPassion]

What are the pros and cons of each?

I’ve looked, I couldn’t find anything discussing this, so I thought I would start a thread.

Please discuss.

[WaterFarmFan]

The biggest difference, other than glycol having a slightly thicker viscosity, is the bath temperature that you are trying to achieve. Ethylene Glycol (anti-freeze) is highly toxic, and thus Propylene Glycol should be used, but is more expensive.

You can simply mix both glycol and ethanol in different ratios, add dry ice and the bath will the reach the minimum temperature that the mixture allows.

From Wikipedia - Mixed Solvent Cooling Baths
https://en.wikipedia.org/wiki/Coolin..._Cooling_Baths

Mixing solvents creates cooling baths with variable freezing points. Temperatures between approximately −78 °C and −17 °C can be maintained by placing coolant into a mixture of ethylene glycol and ethanol,[1] while mixtures of methanol and water span the −128 °C to 0 °C temperature range.,[2][3] Dry ice sublimes at −78 °C, while liquid nitrogen is used for colder baths.

As water or ethylene glycol freeze out of the mixture the concentration of ethanol/methanol increases. This leads to a new, lower freezing point. With dry ice these baths will never freeze solid, as pure methanol and ethanol both freeze below −78 °C (-98 °C and -114 °C, respectively).

Relative to traditional cooling baths, solvent mixtures are adaptable for a wide temperature range. In addition, the solvents necessary are cheaper and less toxic than those used in traditional baths.[1]

[WishDoctor]

NO, the biggest difference is alcohol ignites on fire even in iso. the fog will barely control the fire, I've repeated 3 experiments out back in my wood pile. Dry Ice fog will not put out the alcohol fire.

there is no danger of fire with glycol

yes there are temp differences, as can be found listed in the jpg on mr extractor's site but you honestly don't know your safety.
If you did you would know alcohol and fire is a huge problem.

[Gray Wolf]

Originally Posted by WaterFarmFan

The biggest difference, other than glycol having a slightly thicker viscosity, is the bath temperature that you are trying to achieve. Ethylene Glycol (anti-freeze) is highly toxic, and thus Propylene Glycol should be used, but is more expensive.

You can simply mix both glycol and ethanol in different ratios, add dry ice and the bath will the reach the minimum temperature that the mixture allows.

From Wikipedia - Mixed Solvent Cooling Baths
https://en.wikipedia.org/wiki/Coolin..._Cooling_Baths

Mixing solvents creates cooling baths with variable freezing points. Temperatures between approximately −78 °C and −17 °C can be maintained by placing coolant into a mixture of ethylene glycol and ethanol,[1] while mixtures of methanol and water span the −128 °C to 0 °C temperature range.,[2][3] Dry ice sublimes at −78 °C, while liquid nitrogen is used for colder baths.

As water or ethylene glycol freeze out of the mixture the concentration of ethanol/methanol increases. This leads to a new, lower freezing point. With dry ice these baths will never freeze solid, as pure methanol and ethanol both freeze below −78 °C (-98 °C and -114 °C, respectively).

Relative to traditional cooling baths, solvent mixtures are adaptable for a wide temperature range. In addition, the solvents necessary are cheaper and less toxic than those used in traditional baths.[1]

You can take alcohol lower and still circulate it, but as noted it is flammable.

[WaterFarmFan]

Safety first. Always. Many things with extracts are in fact dangerous, and precautions must be taken, including a healthy dose of common sense. You are very correct to point out the flammability of ethanol, but just as with explosive gases used as solvents, it is not a reason to totally discard it. I have used dry ice and ethanol extensively, and speaking from practical experience, the biggest safety risk is having -78C etoh splash on your skin or soak gloves while handling. You can handle dry ice briefly with minimal effect, but you can be "burned" as the liquid transfers heat from your skin, which the liquid sticks to.

The main point of my post was that the difference in freezing (or lowest temp using dry ice) points of glycol and ethanol is ~110F. This is very large gap and depending on your application, you simply might not need to cool to <-100F, but that you can mix the two to create a bath or recirculate at a variety of temps in between.

[MJPassion]

The flammability of alcohol was my only real concern with using it. However, considering the fact that I’m already playing with Fire by using tane, that concern is more or less mitigated via following strict safety protocols.
Alcohol makes a good bath & get a lot colder than I suspected it would. My -50C IR thermometer couldn’t read the temp. All I got from it was a ‘Lo’ reading. Good enough for me to know I can also run propane in the future, if I decide to go that route.

As far as Glycols go, I automatically go for PG due to EGs toxicity.

Can anybody discuss the handling characteristics of PG?

Alcohol dries (evaps) very quickly, ime & is relatively cheap. Cleanup after an alcohol bath is easy peasy. How does PG compare?

[WaterFarmFan]

Originally Posted by MJPassion

The flammability of alcohol was my only real concern with using it. However, considering the fact that I’m already playing with Fire by using tane, that concern is more or less mitigated via following strict safety protocols.
Alcohol makes a good bath & get a lot colder than I suspected it would. My -50C IR thermometer couldn’t read the temp. All I got from it was a ‘Lo’ reading. Good enough for me to know I can also run propane in the future, if I decide to go that route.

As far as Glycols go, I automatically go for PG due to EGs toxicity.

Can anybody discuss the handling characteristics of PG?

Alcohol dries (evaps) very quickly, ime & is relatively cheap. Cleanup after an alcohol bath is easy peasy. How does PG compare?

You will have to get low temp (-100C or -200C) K Type Digital Thermometer & Thermocouple Sensor Probe to read those very cold temps. Most K Type only go down to -30C or -50C.

As far as PG, it is not sticky or very viscous (like an oil) at room temp. It is more like a thin syrup, and it is easy to clean with just paper towels. It has miscibility with both water and alcohol. You should order a gallon to compare.

https://www.amazon.com/Propylene-Gly...dp/B01MS8F1UW/

I would imagine that adding a decent percentage of PG to ethanol would considerably reduce the fire hazard as well.

[MJPassion]

Cool, thanks for the tid bits WFF.

PG costs about 3x what Isopropyl does but it doesn’t boil off as readily either.

Does a mix give better heating/cooling characteristics than either alone?
I’d prefer using one or the other for simplicity’s sake.