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Excessive water in Petri Dishes
    #1190701 -

I'm having a problem with condensation in my Petri dishes. I wait until the agar cools and solidifies, after streaking the agar's surface I seal them with electrical tape.
I don't just have a few droplets of water on the petri lid, there is a substantial amount of water resting on the agar.
It fucking sucks I have to trash them!
Any feedback is appreciated!
Thanks


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"SO FUCKIN WHAT IF IM A PUPPET SLAVE"

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Re: Excessive water in Petri Dishes [Re: TRIPPYCHIK]
    #1190805 -

turn the plates over (upsidedown)

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Re: Excessive water in Petri Dishes [Re: deanofmean]
    #1190844 -

Ok. So your saying it's cool to leave the water in sitting on the cover of the petri dish.
Could the sitting water possibly casue contams?

Thanks


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"SO FUCKIN WHAT IF IM A PUPPET SLAVE"

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Re: Excessive water in Petri Dishes [Re: TRIPPYCHIK]
    #1191614 -

Anyone else experience this?


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Re: Excessive water in Petri Dishes [Re: TRIPPYCHIK]
    #1191624 -

Cooling the plates in a stack, with all of the plates 'upside down' cuts this problem a lot.

In practice, I have always, always cooled/incubated plates 'upside down'. In fact, 'upside down' is really 'right side up', at least for bacterial culturing.

You will be in a better situation if you do this in regards to condensation. Keep your plates with the agar on top, and the water will collect on the lid below. In the same place you do inoculations [glovebox, e.g.] you can lift the top of the petri [the half with the agar], and slide out the bottom [containing condensation]. Then you can discard the condensation just by dumping it out.

It's obviously better to avoid this situation from the beginning; Anno posted a nice pic where he was cooling a stack of petris with a mug of hot water on top of the stack.

But you'll be ahead of the game [IMO] if you just make it standard to consider 'upside down' as 'right-side up' in regards to petris.

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Re: Excessive water in Petri Dishes [Re: TRIPPYCHIK]
    #1191885 -

What kind of dishes are you using? Do they have spacers between the lid and the dish? These are important since they allow for some evaporation.

Electrical tape? It seems to me that that stuff is not very breathable (unless ? think of type of tape other than you mean).
I use clingfilm to tape dishes. If you cut a small roll (3 cm wide) from a large roll (30 cm, as they are sold) with a sharp serrated knife you have the perfect stuff to tape dishes. Strech it out a bit and use it to tape the lid and dish together (2 times round). Trust me, nothing works easier than this :laugh:

About incubating cultures:If you let the temperature fluctuate too much you will surely get condensation in the dishes. Try to keep the temperature as constant as possible. Incubate the dishes upside down. Even if condensation forms it will not disturb mycelial growth.

If you put something hot on top while stacking the dishes with still warm agar you will also really lessen condensation on the lids. If possible put them in a clean warm place for two days before using. Then almost all droplets should be gone and introduced contaminants will be visible.


When pouring dishes in a flow cabinet this is not necessary. I lay them out on the table top and simply let them solidify with the lids half covering the dishes allowing for great evaporation. This is great because you don't have to let the agar cool. You can pour them straight prom the pressure cooker.

When all condensation is gone the dishes can be used or taped and stored.

Good luck! :laugh: 


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Re: Excessive water in Petri Dishes [Re: Una]
    #1192752 -

I wanna start by saying Thank You all so much for your time and knowldege. I am currently using Pyrex petri dishes.
From now on I'll use cling wrap and seal them upside down.

Thanks!!

Trippy



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Re: Excessive water in Petri Dishes [Re: Una] * 1
    #1194267 -

IMHO The problem with petri dishes is that they are not designed for slow growing micro organisms such as mushroom mycelia. Petri dishes are for bacterial cultures, which only need to be incubated for a couple of days.

But mushroom mycelia often need weeks to colonize a full dish. Petris do not contain enough oxygen for such a prolonged time. Hence, the grower is confronted with the following problem: the dishes need to be sealed to keep out contamination and they need to be open to allow for air exchange.

I think the best solution is to not use petris for mushroom cultivation. Use glass screwcap jars of at least 200ml instead. They are far cheaper than petris but contain plenty of oxygen, so the lid can be screwed down tight. The metal lid has an additional advantage over petri lids: you can make a cellotape-sealed pinhole in it for liquid inoculation without the need to open the jar. And you can make a slightly bigger hole and plug it with cotton wool to allow for evaporation and prevent condensation problems.

It is really funny if you think about it. I have posted about this at the Google newsgroup AltDrugs Mushrooms before: petri dishes are an invention of the late 18 seventies. They were originally meant to study bacterial cultures under a microscope. They needed to be shallow (not deep) so the lense of the microscope could be very close to the bacterial colonies. And the petris didn't have a screwcap because that method to close a container was not invented yet!

The only reason I can think of that petri dishes are used by mushroom cultivators at all is that the early mycologists looked at their microbiology collegues who studied bacteria. The mycologists borrowed their techniques because the bacteriologists were more advcanced at the time. But for some obscure reason the mycologists forgot to update their techniques in the century which followed. To prevenmt this from happening again it is necessary to teach yourself in the historty of cultivation techniques. Always keep asking why you use the equipment you use. How and when and for what purpose is it invented? Never use equipment simply because your teacher did it. Because if you do you may end up with equipment and techniques which are over a century out of date!

Yachaj

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Re: Excessive water in Petri Dishes *DELETED* [Re: mycophreak]
    #13831413 -

Post deleted by flameclown

Reason for deletion: [this post is damn old]


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Re: Excessive water in Petri Dishes [Re: flameclown]
    #13831619 -

First of wait more, agar need to be nice warm so you can hold it in your hand.
Then put it in perti dishes, then put one dish on the other, and dont tape them for god sake Why would you do that?
By puttig one petri on the other only first and last one will condensate.
And dont throw away your agar reuse it.


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By Albert Hofmann :
Been cautious man, I though I would start with a smallest, smallest quantity. Namely I started with 0.25mg.....and my intention was to increase dosage to see if something will happened.
That very small dosage, the first dose of my experiments i planed, was very very strong.

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Re: Excessive water in Petri Dishes [Re: Hofmann1943]
    #13832316 -

1. A good reason to use petri dishes is because you can actually see the culture well.
2. I would recommend not using cellophane or "plastic wrap" if you do not use sticky mats. Mites can get past it. Use parafilm. MITES SUCK!!
3. Condensation is preventable by allowing the agar to cool down till it is almost gel-like before pouring.
4. Do not reuse agar. Thats a bad habit and has bad consequences. Only make up as much as you need by planning ahead.
5. Plastic petri dishes are much better than glass ones.
6. It's ok to tape dishes for storage but make sure to use parafilm after they are inoculated. I don't like to waste parafilm either. It's expensive.

My 2 cents

Edited by Nucleus (01/22/11 04:22 PM)

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Re: Excessive water in Petri Dishes [Re: Nucleus]
    #13832964 -

Nucleus I reuse agar and never had any problem with it.
And plastic petri sucks big time. How can plastic be better than glass?:thumbdown:

just my 2 cents


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By Albert Hofmann :
Been cautious man, I though I would start with a smallest, smallest quantity. Namely I started with 0.25mg.....and my intention was to increase dosage to see if something will happened.
That very small dosage, the first dose of my experiments i planed, was very very strong.

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Re: Excessive water in Petri Dishes [Re: Hofmann1943]
    #13833737 -

:oldthread:

Hofmann1943 said:
And plastic petri sucks big time. How can plastic be better than glass?:thumbdown:


Pre-sterilized plates = saving time...
Saving time = Saving $$$
Plus, the cost on 500-1000 glass petris is outrageous...


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Re: Excessive water in Petri Dishes [Re: total]
    #13835570 -

You could never be sure if Pre-sterilized plates are sterilize enough.
And when you cut agar on plastic plate it leave a mark.
Plus what do you do with them after first use, throw them in garbage?


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By Albert Hofmann :
Been cautious man, I though I would start with a smallest, smallest quantity. Namely I started with 0.25mg.....and my intention was to increase dosage to see if something will happened.
That very small dosage, the first dose of my experiments i planed, was very very strong.

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Re: Excessive water in Petri Dishes [Re: Hofmann1943]
    #13835916 -

Pre-sterilized plastic dishes have never let me down, and I've used tens of thousands of them over the years.  They're far superior to glass for mycology use.  Also, since I didn't get involved in this necro'd thread earlier, the advice above to store petri dishes upside down for mycology use is flat-out wrong.  Always store petri dishes right side up.  Wrap with parafilm to prevent contaminants, and keep them in a vertical stack to prevent condensation.
RR


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Re: Excessive water in Petri Dishes [Re: Hofmann1943]
    #13837202 -

Hofmann1943 said:
You could never be sure if Pre-sterilized plates are sterilize enough.
And when you cut agar on plastic plate it leave a mark.
Plus what do you do with them after first use, throw them in garbage?


To be honest, you could never know if your being sterile enough...
Id much rather trust gamma radiation over my sterilizing my own expensive glass plates :shrug:
And yes, they go in the garbage...but after they are USED/Contaminated....not after a "first use" :lol:
Thanks for stepping in RR...Thread is OLD!


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Re: Excessive water in Petri Dishes [Re: total]
    #13847410 -

If you get parafilm keep it in a sealed ziplock.
  I only learned these cleaning methods when i was given 500 dusty dishes.

Not perferable but its pretty easy to clean used plastic petri.  A soapy water, rinse will do it.  If u want three 60 sec runs in the microwave in an ovenbag.  keep the bag closed till ur ready 2 pour agar.  Microwave lids seperate from the bottoms....  or wash with soapy water and rinse with alcohol in a bag or h202 let moisture evaporate from storage bag b4 use...

Edited by aris (03/21/11 05:32 PM)

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Re: Excessive water in Petri Dishes [Re: aris]
    #13852250 -

well i guess i never loved plastic dishes, because i never needed so many of them.
I have bout 20-30 glass dishes ant that is that.
Plastic is certainly good for hunting wild mushrooms.

Just one Q :why use parafilm? Isn't petri dish constructed like this so no contaminations can come in?


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By Albert Hofmann :
Been cautious man, I though I would start with a smallest, smallest quantity. Namely I started with 0.25mg.....and my intention was to increase dosage to see if something will happened.
That very small dosage, the first dose of my experiments i planed, was very very strong.

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Re: Excessive water in Petri Dishes [Re: aris]
    #13852565 -

aris said:
Not perferable but its pretty easy to clean used plastic petri.  A soapy water, rinse will do it.  If u want three 60 sec runs in the microwave in an ovenbag.  keep the bag closed till ur ready 2 pour agar.  Microwave lids seperate from the bottoms....  or wash with soapy water and rinse with alcohol in a bag or h202 let moisture evaporate from storage bag b4 use...


IME this is a fail.  Plastic is porous and you can't wash bacteria out of it with any reasonable amount of effort.  I've tried washing, then sanitizing with alcohol, and I consistently got patches of bac growing under my poured agar, as well as at the edges.  I don't know whether or not the microwave might help though, TBH.

I tried to be ecologially conservative by recycling them, but soon realised it was a waste of time, effort, and agar.  Nowadays they get used once.  I just try to buy them in bulk (boxes of 500) and they're cheap that way.


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Re: Excessive water in Petri Dishes [Re: andymc]
    #13852712 -

Agreed.  Plastic petri dishes are a one use item.
RR


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