rrkss
Hazard to Others
Posts: 193
Registered: 18-12-2009
Member Is Offline
Mood: No Mood
|
|
Charred Glassware
How would one get charring off glassware after soap and scrubbing failed without using something dangerous like chromic acid?
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
"Fire. And lots of it." - Dr. Julius Hibbert
Of course, you really ought to have an annealing lehr to do that to glass. It would do a fine job, though.
The whole point of "char" is it's tenacious, which is why ordinary chemicals don't do jack and why H2CrO4 or H2SO5 is necessary.
Oh, in case it's actually something tarry and not entirely charred, try a variety of solvents. Pet ether, acetone, THF, etc...
Tim
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
There are several threads already on cleaning glassware. Use the search button.
It usually takes something corrosive, like 10% KOH in ethanol. Soak a day or two, pour out and save for later use. Rinse with HOT water, and if need
be, apply a brush and some gentle scouring powder.
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
Shaking the flask with acetone and salt in it is pretty good as far as gentle abrasion goes. You could always sit it on the mag stirrer overnight.
|
|
|
psychokinetic
National Hazard
Posts: 558
Registered: 30-8-2009
Location: Nouveau Sheepelande.
Member Is Offline
Mood: Constantly missing equilibrium
|
|
Go the whole hog. Melt it down and re-blow it 
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
|
|
|
rrkss
Hazard to Others
Posts: 193
Registered: 18-12-2009
Member Is Offline
Mood: No Mood
|
|
Sodium Hydroxide in Ethanol seemed to work well in removing most of the charring but not all of it.
|
|
|
Mr. Wizard
International Hazard
Posts: 1042
Registered: 30-3-2003
Member Is Offline
Mood: No Mood
|
|
I've had good luck removing age hardened paint, charred grease, 50 year old oil and grease with a liberal application of oxygen through a cutting
torch. After getting over the shock, think about it.
I have started the cutting torch, then quickly, with no preheating, apply it and the oxygen to the organic material you want to remove. Don't linger
in one place. This has worked well for me in removing organics and even Bondo from thin metal. Often the metal is just warm to the touch after the
removal. Cast iron parts often look brand new after a cleaning like this
A modification of the practice would be to flush the container with O2 while gently heating the area, from the other side, gently oxidizing the
target material. Don't use this where there is a lot of organics or you will just catch it on fire and ruin your glass.
A small ozone generator, with a piece of aluminum foil hooked to a HV source behind the offending stain, and a water bath acting as the other
electrode would also effect some oxidation. I know it works in air, because it bleached some capacitor dielectric I was using. The effect could be
improved using a gentle flush of O2.
|
|
|
NADPH
Harmless
Posts: 11
Registered: 1-1-2010
Member Is Offline
Mood: No Mood
|
|
When usual methods fail I use piranha solution by mixing H2SO4 + H2O2 in situ and gently heating. It helps. But be careful with this thing...
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
I would strongly consider using Caro's acid as the last resort, and only after you've physically removed as much as possible. Making and heating such
a solution is a recipe for a violent explosion that probably won't be in anyone's best interests. Piranha solution is no joke, I would only use it on
precleaned glass.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
