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making 0.15% agar for seedling plates - (Dec/26/2006 )

I could use some help on this. I am making up 0.15% agar for general lab use and for aiding in plating some of my plant seedlings. I measured it out as putting in 0.15g in 100ml to make up a 0.15% agar stock. I use Bacto-agar.

When I mix the agar into the ddH2O, the agar looks like snowflakes swirled around in water and not actually dissolving in the ddH2O. I see white foamy bubbles on the top of the water. Is this a common thing to see or do I have contamination?


Agarose doesn't actually disolve in water. Agarose is actually compose of long polysaccaride chains which can form bonds with water. Bonding with water hydrate the chains and you get a gel.

What you need to do is heat your agarose mixture close to boiling.
First weigh your bottle. note reading

Then heat up your mixer close to boiling point. Swirl bottle. Be very careful when doing this as agarose gels are very prone to superheating. Ie they can get hotter beyond their boiling point. Thus any disturbance at this point sends the gel into a furious boil. With much agarose shooting out the bottle, very likely burning anybody nearby.

Re weigh said bottle and top up with sd water to compensate for any lost. Careful.. superheating
Then cool down the agarose gel in a water bath set around 50 - 55 Celsius. Agarose sets below 50 Celsius.

I am not certain what the bubble you are observing. It just might be agarose powder floating on some bubbles.