feipoa wrote:Sorry, when I wrote "inorganic" solvent I meant that it does not dissolve organic material well, not that the solvent does not contain organic constituents. I recall my professors in graduate school always making a point to not use IPA to clean the finger prints or other oils off our gold nano arrays because it was "not an organic solvent." Were they wrong? Or are you wrong? I am confused. I recall the protocol was to use acetone to clean off the oils, then use IPA to clean off the acetone. Sometimes we also used a "piranah etch" instead of the acetone (sulfuric acid + hydrogen peroxide).
So my understanding was that if you are going to use IPA to clean oils (i.e. for materials which will be eaten by the acetone), that pressure needs to be used to sheer the oil away or that the oil needs to be picked up, for example by a q-tip or similar. Unfortunately, that can leave scratches, hence the need for an "organic solvent", like acetone. I think I will do a little experiment tomorrow with some wheel bearing grease in a dish to see if IPA dissolves it at all. Then compare it with acetone.
The results of my tests were not entirely inconclusive, however based on what I have read online, acetone is quite a bit better at removing oils than Isopropyl. In my tests, neither IPA, nor acetone (by way of a nail polish remover bottle), would dissolve some petroleum-based grease in a dish. I used 99% IPA and my wife’s acetone-based nail polish remover. I’m not sure how the concentration of acetone in nail polish remover compares to lab grade acetone, but online suggests it can be 30-60%. Since the grease did not dissolve in IPA or acetone, my first thought was that if you simply soak your dirty parts in IPA and do not apply ample sheering force (from the squirt bottle) or apply physical contact to remove the grease, that the grease will remain on the surface after the IPA drys. Swishing the IPA around in the dish did not lift the grease from the surface.
The grease did appear IPA-phobic, that is, when I spread some bearing grease all over a glazed ceramic dish and stirred it with a stick, the grease would clump together into a single mass. However, even with the grease on a smooth surface, I had to use physical contact before the grease would lift from the surface of the dish. I am sure your results would vary depending on the type of grease (specific weight, constituents) and time/agitation.
I then proceeded to use some non-chlorinated brake cleaner. The grease dissolved pretty well in this case. An online search revealed that non-chlorinated brake cleaners often contains heptane and acetone. Perhaps the concentration of acetone in my wife’s nail polish remover was too low to be effective.
Since you generally do not want to use acetone on PCB’s (damage to plastics and resins), I thought I would try some other cleaners to see how they were at dissolving my sample grease. I tried some citric acid and acetic acid, but the result was the same as with the IPA. Mean Green did an ok job at dissolving the grease, but not nearly as good as the brake cleaner.
I used a few different test samples: a thin layer of bearing grease, a thick blob of bearing grease, vasoline, 3-in-one oil general purpose hinge oil, and sunflower oil. The best case was the thin layer of red bearing grease because I could visualise it in a white ceramic dish.
Further debate on IPA vs. acetone for cleaning oils, if you are interested. http://www.eng-tips.com/viewthread.cfm?qid=85538 This comment in particular, “I've used both for cleaning/degreasing and find acetone to be far better at actually dissolving and stripping "grease" than IPA. Non-polar, non-water soluble solvents like toluene etc. are better still.” I used toluene once, it worked well. I’m not sure how easy that is to get ahold of though.
Skyscraper wrote:When water isnt enough I use White Gas as I often find ISOpropanol too weak when it comes to dissolving tar.
Is that the fuel used in backpackers stoves? I recall purchasing "white gas" for my stove and should still have some. Do you recommend it for cleaning PCBs? I’m interested in finding a solvent for PCBs which does a good job at disolving oils but without needing to use physical contact and will not eat away at the PCB resin (like acetone will). I was also thinking of chlorinated brake cleaner might work well as I do not believe this contains acetone. It is cheap and flows out of the can with some force. Safe/cheap alternative to using contact cleaner, or just a bad idea?
I like PCBONEZ's idea of using Mean Green, but without using the dishwasher. If my wife found out, we would be buying a new dishwasher.
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