Agar plates - how old is too old?

[Merilyn1]

Just reaching out to see what your thoughts are on how old is too old for an agar plate?

Long story (maybe it should be in the "just a whinge" section). Ext Science student asked for a heap of plates. Year 12 Bio teachers also asked for heaps. Ext Sc student used 10 then dropped the subject. Bio teachers only used half what they ordered.
Bottom line - I had about 30 left over.
Year 10 teacher asks me the following week if one of her students could have agar plates for their SRP (we have rules about this, before you jump in!). All was okay for the student to have the plates.
Plates were made in March. Then holidays came. To be honest, the plates have sat in the fridge and I'd mostly forgotten about them, apart from an occasional thought of chucking them out. I'd assume the student had changed their mind.

So today, two months later (I told you it was a bit of a whinge), teacher proudly tells the HT that the student is doing really well (all thanks to the teacher I bet) and the student is nearly ready for the agar plates.
How many? I asked - oh maybe 6 or 8 or 10.
When? I don't know she says.

So, do I really want to drag out all the gear for 6 or 8 or 10 plates?
Could I give the student the ones from the fridge?

Any thoughts on when old is too old??

[LabTechBrooke]

I believe that if they haven't grown anything, haven't dried out or gotten too wet, then they are fine for up to 12 months.

They should be fine.

[bigmack]

Agree , if they aren't moldy use them .

[Merilyn1]

Thanks guys! Good to have back up to my thoughts. It's Year 10, not like they're working on a PhD.

I'm waiting to see the nose of the teacher get turned up!

[RosalieL]

yeah, if they still look good, just use them!

[Merilyn1]

I've chucked a couple of them into the incubator. Waiting to see the "magic"!

[RosalieL]

Science Assist says to use within a month to prevent drying out. I'd say if it isn't dry it should still work! I'm interested to hear your results

[LabbieSeth]

Hi all, I was just wondering if anyone has an idea on what the shelf life is for 'Agar 1000 Gel' and 'Nutrient Agar'? Or if it has a shelf life at all? Myself and the other labbie have prepared quite a few agar plates for classes this term and, in my opinion, the growth on the plates has been a bit lack luster for a lack of a better term. I am trying to narrow down the reasons for this and thought the agar powder may be too old and therefore less effective in acting as media for microbes to feed off in order to grow efficiently.

[bigmack]

We had a bottle of nutrient agar at old school that was so old , I had to chip lumps of it out with a metal spatula.
Never failed to make great cultures .

We did get a new bottle circa Covid . Teachers did notice that there was less activity after Covid . We put that down to increase in cleaning and improved personal hygene . Who knows .

[PeterK]

We also had poor growth on our plates for a few years, tried a number of different things to fix it. Ended up changing the supplier of our broths and instantly perfect plates.