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People have been wondering how long the phenolphthalein agar lasts for - I had some in the fridge when I started at this school in 2016 and didn't have to make more until this year. It worked perfectly and the only reason I had to make more was because it went mouldy.

Marama T wrote: ↑27 Aug 2019, 08:17 People have been wondering how long the phenolphthalein agar lasts for - I had some in the fridge when I started at this school in 2016 and didn't have to make more until this year. It worked perfectly and the only reason I had to make more was because it went mouldy.

That's funny Marama , I just ditched a couple of icecream containers full of moldy stuff myself a few days ago . It sure does last a long time in the fridge but yup....it goes moldy after a while

i know this is a old old post but i have just came across a great idea of how to prepare the squares for the diffusion experiment.
K mart have silicone ice-cube molds that are perfect for the 3cm square cubes then students can cut another one down to get a 2cm square and 1cm square.

That's a great idea Kimmy

Labbie wrote: ↑28 Jul 2020, 14:01 That's a great idea Kimmy

yes when i read it i thought, wow what a great idea.

There are also silicon ice cube trays perfect for 2cm cubes and 1 cm cubes - so much less waste!

It's my time of year to do this again. Last year I saved the leftovers for the first time, and it seems to have kept well in the fridge. For any others that do this, what method do you use to re-melt the agar for pouring? I'm reluctant to use the microwave method since we don't have our own science microwave; I would have to use the staff room ones people use for their lunch, and I have concerns about using science equipment in there, spillage, etc.

Good point Milo, we got a new one for the staff room, so I was able to take the old one just for the prep room. One of the best things we ever did.

Short of using the microwave, perhaps heating in a water bath?

I couldn't manage without my cranky old microwave

It takes an age without a microwave......just sayin'!!

Indeed it does. I ended up buying a new microwave for us last week! Now I just need to make sure nobody uses it for their lunch...

Good one Milo, is it in the prep room? We had a sign on the door of microwave, Needs deep cleaning if used for food.

Yes it's in the prep room, which directly adjoins the Science office. For now I've just written on it in texta, need to get around to making a sign.

Hey,

So I've got this agar from 3-4 weeks ago. It's been stored in the fridge uncovered and has cracked and come away from the edges as you can see.
How do you all store yours for the next time someone wants to do this?
Is it past saving now?

Thanks

Wrap it up in a few layers of cling wrap. This will help although I've never had to keep it longer than a few weeks.

Hi Emma,
It doesn't really last long. I do remember when I needed to keep some for later that if you keep putting phenolphthalein on top it helps to keep the colour and stops it drying out but I don't remember how long you can continue this. I don't remember keeping it for more than a few days to a week.
Rosalie

If you remelt it and put it in a bottle it will last until next year!

WOW, milo, how do you melt it, water bath?

The microwave when no one is looking??
(Actually - I probably wouldn't put this in the microwave with the chemicals it contains).

As documented in this thread I bought a microwave solely for use in Science prac prep! Whenever I have to deal with agar I feel very appreciative that I have it.