Making Agar Slants (Slopes) - In Pictures

[floydmeddler]

Right. Decided to give Agar a go. Scales are at a friend's so used teaspoons.

Made 100ml of wort/agar solution:

4tsp DME and 1.5tsp Agar. Probably a little more agar than what was needed but hopefully that won't be a problem.

Just waiting for them to set now then will inoculate a few.

[floydmeddler]

Right, I'm completely sold. These have set ALREADY! Have placed them upside down to allow the condensation to run into the lids. Was thinking about dabbing it off the lid with a piece of kitchen towel made slightly damp with Star San?

Any thoughts?

[Bobba]

Hey, I've got a few questions regarding this lot.
- Are there any disadvantages to using Petri dishes over slants?
- If you you pre-sterilised Petri dishes, and I boil the Agar-wort for a good 15 mins before adding, can I get away without autoclaving?
- Where 's the best place to get metal inoculating loops?
Thanks as always!

[floydmeddler]

Hey, I've got a few questions regarding this lot.
- Are there any disadvantages to using Petri dishes over slants?

Only one I can think of is that the slants are kept air tight. Purpose of petri dishes is to isolate the colonies in order to then transfer them over to slants for storage.

Only question I can answer - sorry.

[tim]

Right, I'm completely sold. These have set ALREADY! Have placed them upside down to allow the condensation to run into the lids. Was thinking about dabbing it off the lid with a piece of kitchen towel made slightly damp with Star San?

Any thoughts?

Have also just given this a go (thanks for the really informative thread!!) and have noticed small amount of condensation in the tubes - is this a problem or is it important to get rid of it before using?
Tim

[floydmeddler]

Have seen slants with condensation before and have used them. They've been OK - just messy looking.

With this current batch, I sat them all upside down for 24 hrs then undid the lids and quickly poured off the water. Still a little in there but much tidier. My Gelatine batch didn't have this problem. Odd...

[Bobba]

I've read that you can leave them upside down, with the lid slightly undone, and the slants covered (to stop contamination by dust) for a couple of days and the condensation should evaporate.

[tim]

Thanks guys - will give em a go then!
Tim

[Bobba]

After obtaining a pressure cooker last week (reduced currently in Morrisons), I gave this a go this afternoon.
I have some pre-sterile plastic Petri dishes and plastic tubes, so made some slants and plates to work with. I dont think either container will withstand the "autoclave" so as pre-sterile, as decided to simply autoclave the agar/wort and then pipette 20ml's into the flasks and Petri dishes.

The plates seemed to have turned out great. The slants however didn't work out as well - the surface is covered in quite large bubbles (not a nice flat agar surface to work with) and they is also very visible clumps of break material.
I did notice the break as I was filling them up, but decided to ignore it and carry on! Not sure how much of a problem it is?
However, the bubbles on the surface I suspect are a show-stopper are they not? Perhaps I just need to optimise my pipetting technique for less bubbles - it just seems a bit tricky as you can't really run it down the side of the flask as one doesn't want the agar getting to places other than the slanted base.
Any tips here?!

[Wolfy]

Right, I'm completely sold. These have set ALREADY! Have placed them upside down to allow the condensation to run into the lids. Was thinking about dabbing it off the lid with a piece of kitchen towel made slightly damp with Star San?

Any thoughts?

The condensation can contribute to the spoiling or contamination of the slant, depending on how they are made the wort/agar may absorb the excess liquid or you may need to tip it out. If you sanitize the outside of the vial, have a flame source close by and carefully open then tip out the excess moisture you should be fine, dabbing might open the risk of infection a little more.

Hey, I've got a few questions regarding this lot.
- Are there any disadvantages to using Petri dishes over slants?
- If you you pre-sterilised Petri dishes, and I boil the Agar-wort for a good 15 mins before adding, can I get away without autoclaving?
- Where 's the best place to get metal inoculating loops?
Thanks as always!

Petri dishes have a larger surface area, which means they dry out more quickly and there is a higher risk of contamination when you have them open for use, they are also harder to seal and keep air-tight which also increases the risk of infection. So, in general, Petri dishes are not as useful for long-term storage.

If you are lucky you can get away with anything, however, nothing beats super zealous overly pedantic sanitation in order for you to keep your slants in the best condition possible. It may be that your suggestion works well, most of the time (or even all of the time) but it does open the door just a little to the risk of infections.

You can make your own metal loops (as per the details in the other sticky thread here).

After obtaining a pressure cooker last week (reduced currently in Morrisons), I gave this a go this afternoon.
I have some pre-sterile plastic Petri dishes and plastic tubes, so made some slants and plates to work with. I dont think either container will withstand the "autoclave" so as pre-sterile, as decided to simply autoclave the agar/wort and then pipette 20ml's into the flasks and Petri dishes.

The plates seemed to have turned out great. The slants however didn't work out as well - the surface is covered in quite large bubbles (not a nice flat agar surface to work with) and they is also very visible clumps of break material.
I did notice the break as I was filling them up, but decided to ignore it and carry on! Not sure how much of a problem it is?
However, the bubbles on the surface I suspect are a show-stopper are they not? Perhaps I just need to optimise my pipetting technique for less bubbles - it just seems a bit tricky as you can't really run it down the side of the flask as one doesn't want the agar getting to places other than the slanted base.
Any tips here?!

Polypropylene (PP) plastic can be heated and autoclaved, where other plastic such as LDPE or Polystyrene (PS) cannot, so it just depends what your dishes are made from (I think most plastic Petri dishes are PS).

If you are getting bubbles it may be that your mixture is a little too solid, having cooled too much or used too much agar. If the wort/agar is still very liquid you should be able to pour it into the tubes (tap them a little to remove any trapped air) and then lay them on an angle without any concern about bubbles. Any large clumps (of break or other material) should be removed before you mix the agar, else they may also cause problems.

[swheatbeer]

sterilising in a microwave

I dont have a pressure cooker but do have a baby so I have a microwave steriliser. has anyone put the slopes in a microwave steriliser? it works for babies bottles

[Wolfy]

To be sterilized items must be heated for "15 minutes at 121 °C or 3 minutes at 134 °C".

I'd guess that the microwave bottle 'sterlizer' (like the electrical baby bottle steamer I have here) is simply a convenient way to heat treat the baby-items with steam at or about 100°C which would kill most things, but not all. If so it's one of those things that works pretty well, especially if you do not have an autoclave or pressure cooker, but it's not ideal.

[barney]

Thanks for guide, inspired me to give it a try.

[greenxpaddy]

Q. Are polystyrene test tubes able to withstand 121C?

[gregorach]

Q. Are polystyrene test tubes able to withstand 121C?

No.

Nalgene have a very useful list of which plastics can be autoclaved here.