91% Alcohol vs 99% Alcohol

I was just reading the warning on the left side of the label, I especially love the one about keeping it locked up and away from children. Also it’s for “Technical Use”, nothing about it being usable for disinfecting.

Most IPA I ever see is in pharmacies and is for disinfecting and cleaning.

I’d guess that’s because alcohol serves different purposes depending on its dilution. 100% isopropanol is a very low electrical conductor, so it’s used to clean electronic components and circuit boards (hence being called “technical” and sold in electronics hobby shops). Add 9% water and it becomes the medical disinfectant sold in pharmacies. At 30% and it becomes “rubbing” alcohol. The water is necessary to avoid drying ALL the moisture on skin. But chemically, it’s all the same exact alcohol. The labels are guides, not rules: “that water says ‘for drinking’, you can’t use it for boiling!”. :wink:

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At what dilution is IPA safe to use in an ultrasonic cleaner?

Here is an interesting article on IPA in ultrasonic cleaners. The really interesting part, is the one dealing with isolating the IPA from the rest of the environment. Basically put the object to be cleaned in a container of IPA, and then floating the container in the cleaner tub which is 1/2 full of water, thereby isolating the IPA container from the actual metal tub.

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If you want to be super cautious you can put the IPA in a ziploc bag (make sure it is thick enough with no leaks) and use water in your ultrasonic cleaner. Put your parts in the ziploc with the IPA then float that in the water. A very similar suggestion to Dudemeister’s above, but with much more available stuff (ziploc instead of beakers etc).

I know people who put 90% straight in the ultrasonic cleaner and haven’t had problems, but there’s never a problem until the first time (and catching on fire doesn’t sound like a lot of fun to me).

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It has been replaced as a cleaner long ago. I read about similar.

Just to add some value, it is recommended to keep IPA at least 30 cm from any electronics.


will this work? $2.50 per 32 fl oz.


Works for me…

Advised distance to avoid fumes from igniting.

started using my form wash with 99% and overtime I’ve slowly diluted it with 91%. Haven’t noticed a change

so might just go with lots of 91% bottles once the 99% quarts run out

I two bucket larger and parts before they go into the wash

And where is the source of ignition, the spark, going to come from?

I’ve had bottles of IPA sitting right up against my PC for the last couple of years, and never had any issues. And the large tubs are also nearby but their lids are closed.

IPA would need a flame or a spark to ignite, and I really can’t think on how a computer, or any modern electronic would provide that spark, unless it shorted out and started a fie of its own. If you’re worried about heat igniting it, the self ignition temperature for pure IPA is 400°C. I doubt any type of device, electronic or otherwise could produce that type of head and not self-destruct.

There is such a thing as common sense and precaution, but it doesn’t need to border on fear and paranoia.

I think you misunderstood my view on this as I am in agreement with you. I came across the information researching IPA. It was a lab handling and use article stating 30 cm from all electronics.

I believe this to be a precaution in the event of the device failing and emitting a tiny spark. Obviously this would be more risky with 99.9% vs. 71% IPA as well.

It would take some Final Destination event for it to ignite from a computer or something similar. I can see it now. Maybe my watercooling loop in my PC springs a leak, the non-conductive fluid meets dust on the motherboard and becomes conductive resulting in a short and spark. Then boom lol.

Maybe my watercooling loop in my PC springs a leak, the non-conductive fluid meets dust on the motherboard and becomes conductive resulting in a short and spark. Then boom lol.

So just use 99% IPA as your coolant, no conductivity = no shorts, duh


Actually, it’s been tried. The problem with IPA in a cooling system like for a PC, is that the pump and piping are usually made of some sort of acrylic plastic. Alcohol (IPA or other types) has an affinity for water and will dehydrate any type of plastics that contain water molecules. This is the reason why why it deteriorates our resin tanks.

So while it does sound like a good thing, especially since Alcohol doesn’t freeze or become viscous at low temperatures , it will eat through the plastic in pretty short order.

Lol it was a nice thought, but I’ve been at the watercooling for years and the only way for IPA to be a coolant would be copper piping. Not sure how corrosion would work though. Also, it does tend to present the same issue of ignition, but just brings the two closer together. I’ve never had any failures resulting in sparking in all my years with the exception of a bad gasket dumping my reservoir into my dusty PSU.

You want to see sparks from a modern piece of SLA equipment? Try plugging the power plug into a SparkMaker with the power on. Just sayin…

I was kinda wondering if it would be possible to recondition the IPA to some degree instead of disposing of it?

I recently acquired the Form Wash which takes up a lot of IPA so I was considering mixing both sides of my Cleaning Station into it but before doing that I calibrated the supplied Hydrometer with a fresh batch of my usual IPA and then tested it on the dirty side of my Cleaning Station reporting it as basically unusable which got me thinking into running it through a Coffee Filter.

10 Filters ( the resin is clogging it up really fast ) and two runs later I was standing in front of a much less opaque solution that was still as bad as it was before so I did a quick search and found that Active Charcoal is being used to clean Alcohol though it mentions being used for crystalline contaminants which I believe does not apply with resin?

Should I consider ordering a distillery kit on Amazon? xD

If something similar hasn’t also been posted here, this document might be of interest regarding exposure to IPA: