Proper agar recipe

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Budzu

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Well I've taken a try at making plates and slants. I've tried a couple different amounts of agar for setting my wort. All the different sources I'm learning from tell me many different things.

One source told me 1.5-2 grams agar per 400ml. These plates ended up a bit watery, and my innoculation loop ripped right into the agar.

Then I tried a different recipe as per Kaiser which was 3-4 grams agar in 100ml.. quite drastically more. This agar came out very very hard. I plated some yeast on these last night. I am worried though that the agar might be too hard to allow the yeast to receive moisture (is this worry warranted?).

Yet another source (Rajotte's book) tells me to use yet another amount (1.2g agar per 100ml wort).

I'm thinking that all these examples are for a particular type of agar. Like store bought stuff versus bars versus lab agar.

I use the basic agar from cynmar. It is in powder form.

Is there anyone with experience using this particular agar? What is a good amount per 100ml? And will my yeast be able to culture on the hard agar? I still have the original 10ml culture tubes so I could streak them out again with a different agar amount np. I should do it within the day though, these 10ml cultures are winding down.
Thanks!
 

raceskier

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I have Rog Leistad's Yeast Culturing for the Homebrewer". His very simple recipe calls for one tablespoon each of agar and DME, plus 1/16 teaspoon of yeast nutrient, per 1 cup of water. I ratio down as necessary.

I use this agar: http://www.williamsbrewing.com/2_OZ_AGAR_P427C108.cfm
(don't know that there is much difference)

This formula has worked very well for me.
 

BioBeing

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1.5 % by weight is what we normally use in the lab to form a solid plate we can store things on, pick from etc.

However, it only a binder (no food properties etc). So "enough to form plates of the consistency you like" is the real answer ;)
 
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