Making IPA Go Further: Tested


Before my local mom n’ pop hardware store magically got their hands on some well-priced IPA, I only had a bottle from the drugstore I purchased pre-pandemic for cleaning, well, random other stuff. I was able to continue my work through the shutdown by getting my own Form 3, but washing the prints that came out of it was clearly going to be a problem.

To minimize IPA usage, I placed my parts into a sturdy ziploc quart freezer bag (seriously, make sure it’s the “heavy duty” kind or you’ll have leaks), and added enough IPA to cover, then sealed the bag, squeezing out every last bit of air I could. I then submerged this into a (non-heated) ultrasonic jewelry cleaner, using the lid to pinch the zipper side of the bag, so the rest hung down into the water.

Apparently, once dislodged, the resin isn’t eager to cling back to the part. Two 180 second cycles with a brief massage in between seemed to do the trick, and my parts fit at the usual 0.05" OD reduction snap fit. I did do a brief rinse using fresh IPA in the wash bottle, perhaps a tablespoon’s worth. Surface finish was just fine, perhaps a tiny bit more obviously pitted than with ordinary washing steps, but overall I was pretty happy. After each print, the used IPA was saved in a waste container. I made that little bottle last!

Now, some safety notes: ultrasonicating flammable liquids is dangerous as hell. Many of these machines easily have the kinetic energy to heat IPA to its flashpoint by the vibration alone. Do not EVER simply fill one of these things with IPA unless it (and I’m serious) is rated as “explosion proof.”

In my method, the danger is minimized by A: using less than 1/2 cup IPA per print, isolating the IPA from air, and submerging the bags in water, which would dilute the IPA and extinguish any flames should a rupture occur. Additionally, the ultrasonicator was only run on my kitchen range, with a fan and the hood going at the same time.

Anyway, should you run into supply issues with IPA and are printing relatively small parts, this method could help. Make sure you do a thorough safety assessment and familiarize yourself with the dangers of flammable liquids first. Use small volumes and only run the machine in a well-ventilated area far from other flammables.

Happy post-apocalyptic printing!