View Full Version : Question: What do you all use to clean your lab glass?

Franklin Fehrman
10-15-2017, 01:11 PM
I have some glass that has the remnants of some high vacuum silicone from an overzealous greasing of the joint and cant seem to get it out from inside. I'm going to try acetone today, but what other solvents do you all use besides soap and water?

10-15-2017, 02:27 PM
It depends on the nature of what is stuck inside the glass. For organic residues, organic solvents like alcohol, acetone, benzene, toluene, xylene, etc. are often used. Sometimes hot concentrated sulfuric acid is also useful to remove organic residues. For inorganic residues, solvents like water and the several strong or "mineral" acids are useful.

10-15-2017, 02:27 PM
Some of people in my land use chromic compound to clean dirty glass if common water/soap don't help. Chromic compound consists of:
1. Water - 100 g.
2. Na2Cr2O7 - 6g.
3. H2SO4 (96%) - 100 ml.
Some people, however, find it cheaper to throw very dirty glass away and buy new one rather than waste time and reagents to clean stuff.

10-15-2017, 02:33 PM
Some people, however, find it cheaper to throw dirty glass away and buy new one rather than wasting time and reagents to clean stuff.

That's great for cheap soda-lime glass bottles, like the ones used for bottling juices and teas, that you can improvise to use for many experiments, but hardly an approach that most people can afford when it comes to professional borosilicate glassware (specially the more expensive pieces that have ground glass joints.) The only way I throw those is when they actually break and are no longer usable.

10-15-2017, 03:27 PM
For the mineral Sulphur (S) use household bleach.

10-15-2017, 11:03 PM
I never had to clean silicone from lab glass, but some of my closest friends are into non-digital special effects for cinema (props, you know, like making the mask of a monster or a scar or a zombie, etc).

I have helped them several times just for fun's sake. The "good" props are done with silicone (the lower cost ones with other materials). Making a prop involves making a mess, so it's always necessary to clean afterwards. Silicone is the hardest to clean of all the materials they use, but all the ones I know who are into making silicone props for cinema clean it with Acetone (pure acetone, I mean 100% or close to such thing, not 10% acetone). So acetone works for silicone, I've cleaned tables, floors, shoes and whatever from silicone stains several times... Acetone.

[disclaimer: the fact that I have friends who work in the area of props for cinema is yet another indicator that I am into satanism... the hints are very clear... or maybe this is a joke because some weirdos are having strange "hallucinations")

Franklin Fehrman
10-16-2017, 01:38 PM
Thank you, all! I had two beakers that had some residual silicone grease run down to the bottom of the boiling flask and not come out with hot soapy water. I followed some of your suggestions with the 100% pure acetone. That seemed to work on almost all of the residue. There was a little bit of calcium salt residue, but I think some vinegar should get that off too. The other method I just tried was starting with a solution of DI water at 60 mL and 60 grams sodium hydroxide and them mixing them into 500 mL of ethanol. I tried that and had some good success. Both were let to sit over night. And cleaned the silicone business.

Franklin Fehrman
10-16-2017, 01:39 PM
Maybe in the future I will use hot sulphuric acid.

10-17-2017, 02:10 AM
Maybe in the future I will use hot sulphuric acid.

Here you have some guides:

I would NOT suggest using hot sulphuric acid unless you have an EXCELLENT protection (a good gas mask, proper globes, proper clothing, etc).
It will do the trick for sure, but it is OK to use safer options first that in most cases will "do the trick" too anyway.
Even if it works, I wouldn't suggest to use Sulphuric Acid as the "standard method" to clean, since in most cases you will find safer ways to do it.

Unless you are very experienced, Sulphuric Acid in not really the "first option" (and if you are experienced, then Sulphuric Acid is not the first option either).

Nitric acid is excellent for removing the dirt from ceramic floors... but you can use soap, bleach or commercial cleaners and the floor will be clean, I don't know anyone who cleans his ceramic floors regularly with nitric acid (which is not surprising, safer products will clean them too and it's more reasonable to go for the safest option).