Many use petri dishes for mushroom work, but I rarely do. Even the cheapest ones are 50 cents each, and not re-usable. A much better option is yer basic glass canning jar variants . . . either cup (8 oz.) or half-cup (4 oz.). It’s a bit more difficult to see what’s growing than as petri dishes, but almost:

This is a recipe for 500 ml, about 1 pint, of agar mix. It will easily make 20 jars, depending on how thick you pour the mix.

Agar is basically the vegetarian version of gelatin. It provides the support, then for food you need something like malt extract. Nutritional yeast is probably more nutritional to you than mushrooms, but it can’t hurt 🙂

10g agar:

Add 10g malt powder:

Very optional, 1g yeast:

Now add 500 ml water.

THIS IS THE IMPORTANT PART (1)! The agar doesn’t want to make friends with the water, so whisk it into the water for TWO MINUTES!

Now, stirring it regularly, heat it until boiling. THIS IS THE IMPORTANT PART (2)! Here you can’t ignore it, because as soon as it gets to boiling, it will boil over and make a mess. So keep an eye on it, and once it starts to boil, don’t let it boil over (duh) and whisk it for TWO MINUTES (at least ONE)!

You already have your jars ready, of course:

Poured:

The great thing about using re-usable jars is that you can pour the agar, then pressure-cook them:

. . . unlike the fraught pouring of agar into disposable petri dishes that can’t be pressure-cooked, and avoiding contamination.

-R