Phenolphthalein agar disaster

[Lyn]

My "you beaut never fail" recipe for phenolphthalein agar went seriously off the rails last week. I was left with four litres of agar the consistency of jam. It is in the fridge at the moment and I am wondering if anyone has had a similar problem. The only thing different this time was that the agar was referred to as "AGAR, coarse powder" and was from Ajax Chemicals. It is not that old and had only just been opened. I had previously been using up old stock of AGAR 750 Gel from Chemsupply and had no problems. Has anyone used the Agar coarse powder and have you experienced any problems? Do we need to be specific about the agar we buy? Does anyone have any bright ideas as to resuscitating "JAM" to a firmer consistency just in case this happens again?
Lyn.

PS. The teacher used potato cubes and salt solution instead.

[SueH]

Lyn
I use the Agar coarse powder. Mine is quite old but works every time.

I use cold water and sprinkle the agar powder over the top while on a hot plate with a stirrer. Cook it until it boils and then allow it to cool to about 60C before adding the NaOH and phenolphthalein.

I used to find if I used hot water the agar would clump and not dissolve as well.

[Lyn]

Thanks for replying Sue. The agar catastrophe is all a bit of a mystery. I used a stirrer hotplate but it takes so long to boil anything in the two litre beakers (anywhere up to three quarters of an hour on high) and then it only seems to simmer. The agar didn't seem to go as clear so perhaps it wasn't cooked enough. Some of the blocks appeared to be set but that was just on the surface. Then when I tipped the containers slightly you could see that the agar looked the consistency of jam. I am still trying to think which corners I may have cut to get the result that I ended up with. I am sure I will sort it out for next time.

Lyn

[smiley]

Could also have been because the moon was in the left quarter of venus, and you walked into the room while casting a shadow over your left shoulder...

Only suggesting possibilities

Cheers, K

[J]

We just successfully completed this prac with agar that I made in the microwave.
Try it, you'll never go back to your old stirrer!!

Julie

[RosalieM]

Ahhh... wouldn't it be nice to have a microwave! I have had 2 agar issues this week. The first time I turned my back for a minute when a teacher asked me for something 'for this lesson' (starting now!) and it boiled over. Then the second time I asked someone to keep an eye on it because I'd forgotten to purchase something and had to duck down to the shop (because I'd lost 2 days on my unexpected excursion to Sydney) and again it boiled over. Still haven't had a chance to clean them up! Might be next week when I get to it...

[sunray18]

Just imagine what bacteria you will find on the agar when you finally get to clean it up!!! It could be amazing - you may find an organism no one has ever discovered yet...it would need a name .. mmm. thinking thinking...anyone got any ideas?

[RosalieM]

That thought occurred to me as I hit submit and I decided sooner is better than later for the clean up. I decided to go ahead and clean up, and already I had some growth on the bench!! Not a whole lot... But better to get rid of it before it has time to get out of hand! I've cleaned up one hotplate stirrer, and the other is about to be tackled... Can't be healthy! Good thing the weekend is coming up

[J]

Bacillus BloodyHelli?
Streptococcus DamnAndBlastius?
Sorry, some of my more imaginative expletives would be inappropriate on this site.

Julie

[RosalieM]

I like your thinking!

[estelle]

Hi,
I have had problems with agar setting the last two times I made it as well.I was blaming the old agar but I am sure it was because I didn't heat it high enough.
The cubes I made last year you could have bounced off the walls but this year mine were like jam as well.
Yesterday I made 30 agar plates and when I went to cover them they were still sloppy even though I used the same amounts as last time. So I reheated it all again and they are all OK. (Keeping it as sterile as possible and haven't had any unexpected growths)
Good luck with it.
Estelle

[kerryw]

Hi there, this is my recipe for agar which always seems to work really well, but before I pour all the plates I will always pour one first as a test to see if it is going to set.

Measure out 1 litre of water, and 20 gms agar powder. Using some of the water previously measured out, I make the agar into a paste. I then boil the remaining water on a hot plate, (but if thats too slow just use a jug or kettle). When the water is boiling I then pour some of that water into the plastic cup with the agar to make a solution. Stir and then pour it all back into the boiling water. It might seem a bit of mucking around but it works! I let it boil for about another minute and then take off the heat. After it has cooled to about 60 degrees I add 40 ml of 1 M Sodium Hydroxide and a small spatula of phenolphthlein powder. It gives it a really deep color.

I would be interested in knowing the microwave recipe as an alternative.

Just out of curiosity has anyone done a RA on making agar?

thanks
Kerry

[SueH]

We just successfully completed this prac with agar that I made in the microwave.
Try it, you'll never go back to your old stirrer!!

Julie

Great if one has a microwave

[J]

Sorry guys. I didn't realise that my old dinosaur microwave means that I'm actually privileged! Someone must know someone who has an old one they want to get rid of. That's how mine got here. Wouldn't dream of using it at home, but it does the job here.

Julie

[whits]

I use the autoclave to mix agar. Powder(any sort) on top of cold water in a flask. It never fails and is sterile!