If you want clean cultures and reliable results, learning how to make agar plates is one of the most important skills in mushroom cultivation. Agar plates allow you to test spores, check liquid cultures, isolate pure mycelium, and prevent contamination before it reaches grain.
This guide shows you exactly how to make agar plates using MEA agar premix, safe sterilization practices, and the correct pouring temperatures.
Start with the correct ratio:
Use 50 grams of MEA Agar Premix per 1 liter of distilled water.
This ratio remains the same for all batch sizes.
Add the powder directly into the water.
This prevents clumps and creates a smooth mixture.
Heat the mixture on medium while stirring continuously.
Once it reaches a light boil, remove it from heat.
Pour the hot agar into a heat-resistant media bottle.
Add a magnetic stir bar.
Tighten the lid about 90 percent so steam can escape during sterilization.
Place the bottle inside your pressure cooker or autoclave.
Sterilize for 15 to 20 minutes at 15 PSI.
Let the bottle cool to around 60°C.
Place it on a magnetic stir plate to keep it well mixed.
Check temperature with an infrared thermometer.
When it reaches about 50°C, the agar is ready to pour.
This reduces condensation and moisture buildup inside plates.
Move your work into a flow hood or still air box.
Open each plate slightly and pour a thin, even layer.
Avoid bubbles and keep plates open for the shortest time possible.
Plates generally solidify within 20 to 30 minutes in a flow hood, and slightly longer in a SAB.
Once cooled, stack plates and seal them with parafilm or place them in gallon bags.
Store them in a cool, dark space.
Correctly sealed agar plates stay usable for 4 to 8 weeks.
MEA, or Malt Extract Agar, is widely used because it provides a nutrient-rich, clean, and slightly translucent surface that supports strong mycelial growth.
It works especially well for:
Use a flow hood or still air box to prevent contamination.
Include the species, date, and transfer number.
Do not leave plates open longer than needed.
Most gourmet species grow well between 70 and 75°F.
Look for:
Clean agar equals clean grain.
Use exactly 50 grams per liter.
Pour at around 50°C, stack plates while cooling, and store upside down.
Slight cloudiness from malt extract is normal.
Small caramelized specks can appear when the agar mixture heats slightly unevenly or when sugars darken during boiling or sterilization. These pieces are harmless and do not affect performance. As long as the particles are uniform in color and not growing or spreading, the plate is completely fine to use.
A flow hood gives the best results, but you can still make agar plates in a still air box.
The key is slow movement, flame-sterilized tools, and stable air.
Transfer to a sterilized grain bag when you see:
Clean agar leads to clean spawn and strong yields.
Agar plates usually remain usable for four to eight weeks as long as they are sealed and stored in a cool, dark place. Keeping them upside down and protected from airflow helps maintain their quality for the full storage period.
It is best to use distilled water when making agar plates because tap water can contain minerals, additives, or chlorine that affect clarity and may change how well mycelium grows. Distilled water keeps the recipe consistent every time.
To reduce condensation, pour the agar at roughly 50 degrees Celsius and stack the plates while they cool. Allow them to fully solidify before sealing them. Storing the plates upside down also helps prevent moisture from collecting on the agar surface.
MEA agar works for nearly all gourmet mushroom species. It performs especially well with Lions Mane, oyster mushrooms, chestnut mushrooms, shiitake, and reishi. These species typically show fast, healthy growth on malt extract agar.
A flow hood is helpful and offers the highest success rate, but it is not required. You can make and pour agar plates using a still air box as long as you flame sterilize tools, move slowly, and maintain stable air to prevent contamination.
Agar plates are ready for grain when the mycelium is bright white, even, and free from off-colors, unusual textures, or bacterial wet spots. A clean plate indicates clean culture and gives you a higher chance of success when you move to grain spawn.
Agar premix should always be added directly into the water. This prevents clumping and ensures the ingredients dissolve evenly, which leads to clear and consistent agar plates.
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