Erlenmeyer Flask Question

[jonocarroll]

I know you like to bag everyone and think your always right

Settle, petal. I only think I'm right when the other person is wrong... and my answer is right. Don't confuse me for a pot-stirrer who has no idea what he's on about. I'm writing this in between marking university physics exams.

Liquid could have and was there from when the missus wiped the hotplates down 5 minutes before i used the flask and the flask was very clean to start with.

So, that just means it was something else.

Bloody physicists you are right there QB...temporary brain fade (or chemists fade ) on the coil thing.

also Leigh has high credentials in this area

And he agrees with me - surely a good reference!

I hear you Leigh, but i deff had water trapped underneath

So, what you had was water trapped between a flask and a hotplate - surely it's pretty clear that the water would have boiled, under pressure, and could have caused the breakage.

Lessons:

1. Don't put your flask on top of a pool of hot water on a hotplate.
2. Don't pretend that it's the hotplate's fault if you do.

Sheesh.

 

[brettprevans]

chemistry and physics (admittedly from yr 11&12). converstion of liquid to gas creates energy (and byproduct). energy has ro go somewhere. some as noice, heat etc. sudden input of energy to flask = crack. my 2c as a non-chemist/physicists

I have gas stove so I dont have to worry about it!

edit: again im sorta just stirring the pot and have no qualificans in this area what so ever

 

[warrenlw63]

Settle, petal. I only think I'm right when the other person is wrong... and my answer is right. Don't confuse me for a pot-stirrer who has no idea what he's on about. I'm writing this in between marking university physics exams.


So, that just means it was something else.



And he agrees with me - surely a good reference!


So, what you had was water trapped between a flask and a hotplate - surely it's pretty clear that the water would have boiled, under pressure, and could have caused the breakage.

Lessons:

1. Don't put your flask on top of a pool of hot water on a hotplate.
2. Don't pretend that it's the hotplate's fault if you do.

Sheesh.

You seem a little passionate about this... Were you attacked by a broken flask and/or mentally-scarred as a child QB? :lol:

Warren -

 

[jonocarroll]

chemistry and physics (admittedly from yr 11&12). converstion of liquid to gas creates energy (and byproduct).

This is where I'll get technical, but I'll be nice about it.

Converting from liquid to gas actually uses up energy to break the chemical bonds. You can observe this by rubbing some water on your skin and blowing on it - evaporation is liquid -> gas, and it feels cooler, not hotter.

What's happening here though is that the change from liquid to gas (with the energy coming from the hotplate) creates a gas that wants out from under the flask. Heat it up more, and you can get enough pressure to break the flask.

I have gas stove so I dont have to worry about it!

+1, though it's not really an option to switch over just for making starters

 

[jonocarroll]

You seem a little passionate about this... Were you attacked by a broken flask and/or mentally-scarred as a child QB? :lol:

Passionate? Yeah - I'm a physicist who actually likes what he does.

Mentally scarred? ... same answer.

 

[brettprevans]

ahh crap I was thinking condensation. see i told you i had nfi what i was talking about. too many yeasr out of the game. and your explanation wasnt too technical for 11/12 level. god if it was there are goig to be a lot of dumb chemists/pysicists out there after they graduate.

yeah i guess trying to convince the missus that the elec stove has to be changed to gas so you can make starters without cracking you flask would be a little hard.

 

[3G]

I have the schott brand and always go from heating on the gas to chilling in water. 2 years of use and no cracks. I wouldnt risk a cheaper thinner flask with boiling liquid.

 

[smollocks]

Since there's a few people here who seem to know what they're talking about...

I know borosilicate should be able to handle direct heat, but clearly some have managed to crack their flasks. Wouldn't it be safer to heat these schotts/erlenmeyers in a water bath, rather than with direct gas or electric heat?

I'm thinking you could just sit the flask in a saucepan of water and boil that. It should give even distribution of heat. You could even sit the flask on a vegetable steamer so it's not in direct contact with the saucepan. From memory at uni this is how laboratory water baths work.

Any opinions?

 

[Josh]

I heat my 3L Simax flask on a flat electric hotplate. Then stick it in the sink and add cold water to the sink once the flask is in it. Haven't had the balls to drop the flask into a full sink.

All working great so far.

 

[MCT]

I go straight from a hotplate to a sink of icy water with my Simex flasks, no problems yet!

 

[Wolfy]

Just a quickie for someone who knows about these things.

Does anyone know the differences between Heinz Herenz and Schott brand flasks?

Are the Schott flasks thicker/stronger or are they similar in quality.

The Schotts cost a lot more so hoping the cheaper ones will be fine.
Will be using them for yeast propogation.

Unlike others in this thread I do not claim to 'know about these things' however, I DO have a bunch of the cheaper flasks (but brought them here in Melb at Science Supply - cheaper than Livingstone) and have used them without problem.
They are totally fine for yeast propagation, I even use mine directly on our ceramic stove, and often shove them in water to cool them quickly.
The only breakage I've had (so far) was when I was washing them in the sink and dropped the heavy 2l flask onto the top rim of the 250mm one.

IMHO, I think you'll find that while 1/2 the discussion in the thread valid, its 95% irrelevant for what you'll end up using them for, so get the cheap ones IMHO.

 

[cubbie]

Making a starter last night in a Pyrex jug and the blasted thing all cracked up when I took it from the gas to a sink of cold tap water. I thought that was safe to do and I have done it in the past. The Pyrex looked clean with no faults.

Anyway just spotted these erlenmeyer flasks which seem very cheap. http://www.labdirect.com.au/storecategory131.aspx

I would prefer a 3L flask.

On a side not measured my test tubes (used for yeast storage) last night and they are 2/3 smaller than i thought they were, surprising I ever managed to grow enough yeast.

 

[leiothrix]

Are you talking about pyrex cooking jugs? I think they changed their glass a few years ago. So older ones will probably fine but new ones probably wont be.

I could be way off with this, but I seem to remember reading it somewhere.


Rob.

 

[cubbie]

Are you talking about pyrex cooking jugs? I think they changed their glass a few years ago. So older ones will probably fine but new ones probably wont be.

I could be way off with this, but I seem to remember reading it somewhere.


Rob.

Yeah cooking jugs, but this was an older one - mother in laws actually, mine is still safe and in one piece.

 

[501]

I read somewhere on yeast farming that the US ones and Euro ones were different.

The US ones shattered iirc.

 

[mika]

Think you've got to be careful about how much cold water you immerse them in.
If the ice water goes above the liquid level of the wort inside, then I could see it getting a differential cooling rate and causing issues.

 

[cubbie]

Think you've got to be careful about how much cold water you immerse them in.
If the ice water goes above the liquid level of the wort inside, then I could see it getting a differential cooling rate and causing issues.

It was just tap water, though that is very cold at the moment and It was below the wort level. Anyway this was not meant to be about the Pyrex, that is gone now. However I wanted to get some feedback on the link I posted.

 

[Bizier]

I use a coil element, but go super slow on the heat, and I have worked out (by very long experiments) where it will just come to the boil, and I set it there. The added bonus of this is long pasteurisation time and also no chance of a boil over... that is unless you chuck yeast nutrients in without thinking like I did a while ago - volcano.