Sciencemadness Discussion Board

Dry Glass with Heatgun ?

LuckyWinner - 30-8-2020 at 12:45

couldnt find exact answers to this.

I know concentrated heat on glass will cause it to break
but could a heat gun on low setting be used effectively to dry
drops inside your RBF, condensers,...?

any other better alternatives then drying glass in an oven?

just use a heavy industrial fan and blow on it for a while?

Metacelsus - 30-8-2020 at 13:01

Yes, we did this in the organic chemistry lab where I worked as an undergrad. A Bunsen burner can also be used; this is called "flame drying."

If it's borosilicate I wouldn't worry about breaking it at all, unless you do something dumb like put it into cold water immediately afterwards.

[Edited on 2020-8-30 by Metacelsus]

Dr.Bob - 30-8-2020 at 16:42

We use both burners and heat guns to dry glass often. For some items we dry in a oven first to 100 C, but once things are set up, we often use a burner, set with a large flame, less oxygen than ideal, for a yellow flame, and just move it quickly over the flask and addition funnel or other stuff, watching for any condensation on the inside, while blowing nitrogen through the apparatus as a brisk pace. A heat gun works as well, just ove it quickly so that it does not sit on one spot too long. Asd the glass warms, you can go over it once more a little slower. Just let it cool under a nitrogen flow a while before adding your ether or hexane. You only need to get the glass above 100 C, you don't need it glowing red or yellow. But I have done that for years without an issue. But don't use a sharp blue flame or hold the burner or heat gun on one spot too long or too close.

Fyndium - 31-8-2020 at 11:52

Quote: Originally posted by Metacelsus  
If it's borosilicate I wouldn't worry about breaking it at all, unless you do something dumb like put it into cold water immediately afterwards.


I have become maybe too paranoid for cracking glassware. So, if we take borosilicate glass and apply a heatgun or open flame directly onto it, should it just heat up and eventually melt if the temp is sufficient, or could it crack? Last time I grew sceptical was when concentrating sulfuric acid, I found it stressing to apply propane torch directly to the flask

metalresearcher - 1-9-2020 at 09:06

Quote: Originally posted by Fyndium  
Quote: Originally posted by Metacelsus  
If it's borosilicate I wouldn't worry about breaking it at all, unless you do something dumb like put it into cold water immediately afterwards.


I have become maybe too paranoid for cracking glassware. So, if we take borosilicate glass and apply a heatgun or open flame directly onto it, should it just heat up and eventually melt if the temp is sufficient, or could it crack? Last time I grew sceptical was when concentrating sulfuric acid, I found it stressing to apply propane torch directly to the flask


I understand. Normally I heat borosilicate (Duran) glass with a non-aggressive liquid above an open flame, but with H2SO4 I would use a stainless steel pan in which you place the flask with H2SO4 and heat the pan with an open flame. The pan acts like a boilerplate.

Frankenshtein - 20-9-2020 at 12:58

I thought people normally put a little acetone in the glass to wash and then just let it evaporate.

Junk_Enginerd - 21-9-2020 at 22:09

Quote: Originally posted by Fyndium  
Quote: Originally posted by Metacelsus  
If it's borosilicate I wouldn't worry about breaking it at all, unless you do something dumb like put it into cold water immediately afterwards.


I have become maybe too paranoid for cracking glassware. So, if we take borosilicate glass and apply a heatgun or open flame directly onto it, should it just heat up and eventually melt if the temp is sufficient, or could it crack?


I've done some basic glass work, and the answer is it depends on the geometry of the glass and how you heat it. Thick glass is more likely to crack, since it makes for harsher gradients and has less ability to flex. Sharp angles makes it more likely to crack. Large objects are more likely to crack. Erlenmeyer flasks for example crack more easily than a round bottom flask. I have accidentally cracked a 250 ml erlenmeyer flask when I was distilling HNO3 from H2SO4+NaNO3, at up to 300°C.

I have never had a test tube break from heating. They can be heated until they melt. They're rounded and quite small. It would take lots of abuse to crack a round bottom flask, like heating it with a small torch in one spot with no liquid to disperse the heat. It may not even crack then, but melt instead.

As for heating with a hot air gun it should be absolutely fine, as long as you make a minimum effort to heat it evenly.

Cou - 22-9-2020 at 00:11

I thought you could also just pull a vacuum on the closed system, which will evaporate all water.
Always use a dry ice cold trap when using a rotary vane pump.

Fyndium - 22-9-2020 at 03:10

Dry ice has always been a huge issue for me. MOQ is 5-10kg and it costs so much it will render anything except high value for profit reactions unbearable because it cannot be stored. Hence I use CaCl2 bath at -30C for cold trap, and if the oil has emulsified or a layer of water, I'll just change it. Paraffin oil is dirt cheap here.

Anyways, my go-to method to dry glassware immediately is to rinse with small amount of acetone and let it evaporate, and sometimes I put an air pump pushing air through to dry them quicker. I also just heat glass in an oven at 50-100C if I need them dry soon.

Compressed (dry) air works whenever it is available. Blasting 8 bars of air will simply blow most of the moisture the hell out, and the rest will quickly evaporate. Must be careful with closed and fragile vessels though, since the pressure and sheer velocity can break stuff and if you're not careful, stuff may even blast off your hands. :D

pneumatician - 22-9-2020 at 11:00

put a little etanol, spread it well and start fire.