I’ve heard of numerous methods for removing pesticides from glass after heavy contamination. Most of which involve boiling solvents through flasks and pieces while they drip the solvent back out. (Typically flasks are held upside down.)
One other one I’ve heard is the use of sodium hypochlorite (bleach) at night cincentrations. Filling the system with it and allowing it to soak for multiple days. Then washing clean with distilled water.
I’ve also heard that glass is impossible to clean and once glass is dirty it’s always dirty.
I use HCL followed by NaOH. Pretty serious stuff, there’s some safety requirements, but it definitely seems to clean up any pesti residue. I’ve tested this by soaking in warm etoh, reducing the etoh to minimal then testing for residuals. @Photon_noir mentioned drain cleaner would destroy myclo in the saline after “degumming”
I’ve been up all night and finally about to sleep… but here is some info maybe on alkali attacks on borosilicate glass.
What pH do you clean with? I used to recommend the acid/base water washes for cleaning flasks but have been warned multiple times about dissolving glass in strong hydroxide solutions. It comes down to concentration, temperature, and time, like most reactions…
I have a fairly straightforward SOP. For SPD boiling flasks, I add warm DLimonene while the glass is still hot from the run (around 180°C) and flush out any residual SPD waste. After the glass appears free of visible contamination, I pour a little bit of 99.9% acetone + about a cup of course rock salt and swish it all around the interior of the glass. The rock salt acts like a pumice and the acetone (the most polar solvent) will dissolve any residue broken free by the abraisive salt crystals. I then flush out the salt with some clean acetone, rince twice in hot water, then add a thin layer of alcohol with a wash bottle to dry out any remaining water inside the flask. Always let flask dry upside down so any moisture can drip out of the neck(s). You may use a heat gun to assist in drying but be aware of solvent vapors! Cheers
I’ve always used EtOH to remove oil residue, then flushed with excess H20 and soap. I don’t seem to see a lot of cross contamination. Do others avoid simple methods like this? I haven’t run into problems yet.
I’be done some weird experiments that require more aggressive cleaning methods, but generally, soaking in ethanol, maybe a light scrubbing, and rinsing with fresh ethanol in an angle-necked sprayer works well.
I remove as much of the waste as possible, flush with ethanol. Then I put it it in my oven. Let it slowly ramp up to 565c. It’s hold that temp for 2 hours then slowly cools off.
You ever get breakage or stress from heat cycling? Have you got a polariscope? Have you looked at the stress regions before and after? I am interested in this cleaning method. http://www.davebross.com/GlassTech/polariscope.html
Cheap glass will sometimes break. At 565c it re aneals the glass and removes all of the built up stress. Our processes, especially a short path create localized stress areas in the glass due to the fact that the entire glass piece does not heat evenly.
With ceramic and any crystalline/glassy material for that matter, annealing at an elevated temp for some time allows the individual domains at a microscopic level to align and relieve any built up stress. Annealing at higher temps reduces the amount of time needed to relieve this stress as long as you do not hit the softening point of the glass (2/3 of the melting point temperature). This is common practice in computer materials research where stress has large implications.
So far I have had no sagging of round bottom flasks,
Make sure your kiln is vented to outside, it will smoke a bit. I have mine programmed to turn on at 9pm and run when everybody is out of the building. We have had great results with this process and my lab techs love not cleaning my boiling flasks. a 20L is a bitch to clean.
