Urban Spore

How To Prepare Agar

agar plate for mycology

What Is Agar?

Agar is produced from a red algae, known as agar-agar in Malay. This jelly-like substance has  been used for numerous applications as an ingredient in desserts, laxative, appetite suppressant, stabiliser in jams, preserves, ice-cream and as a clarifying agent in brewing.

It’s vegetal origins make it a popular substitute for animal gelatin amongst those following a vegan diet.

It’s qualities are believed to have originally been observed in 1658 by a Japanese inkeeper, Mino Tarōzaemon who had noticed how his seaweed soup had gelled upon being left overnight. Despite this it wasn’t until late in the 19th century that it was used as a solidified medium for microbiology. This use was first noted by German microbiologist Walther Hesse after the suggestion made by his wife, Fannie Hesse in 1882.

red seaweed for making agar

Why Use Agar To Grow Mushrooms?

Agar is used in the cultivation of mushrooms in order to store cultures for long-term use and create mono-cultures free from contamination. 

It’s strongly recommended to germinate spores on agar before use. Spores are often accompanied by pathogens like yeast and mould. By cultivating mycelium on agar plates we can visually identify contaminants with ease allowing for the cultivator to make a clean transfer to a new agar plate.

Agar plates are also used for making fungal clones. A clean fragment of the mushroom fruiting body can be placed on agar to grow rather than germinating spores. This gives the cultivator and advantage in isolating any potential contaminants if present. 

Slimline pyrex media jar for agar

Is A Flow Hood Necessary?

Using a laminar flow hood is beneficial to the production of agar plates. Sterilised media is highly susceptible to contamination. In the absence of a flow hood all sterile transfers should be undertaken in an enclosed space with minimal airflow such as a bathroom.

What You'll Need

Finding the right gelling agent for mycology can be difficult. That’s why we use the best quality premium agar agar powder for mushroom growing in this easy to use, resealable jar.

Step 1. Weight Dry Ingredients

Using precision scales weigh light malt extract and agar powder. Add dry ingredients to heat proof media jar.

Step 2. Measure Boiling Water

Measure hot water in grams using kitchen scales. Add to media jar containing dry ingredients and mix well until dissolved.

These laboratory standard slim line Pyrex media jars make pouring agar a breeze.
Easy hold handles for easier, more efficient pouring with less risk of spillage.

Step 3. Sterilise Agar

Pour dissolved agar and light malt extract mixture into bottle for sterilising. Place lids on media bottles. 

Sterilise agar mixture for 20 minutes at 15PSI. Allow to completely depressurise or wait 1 hour minimum before opening pressure cooker.

Step 4. Cool Agar (Optional)

Place bottle of hot agar mixture in a warm water bath. Use a thermometer to monitor temperature. The agar mixture will measure the same temperature as the water bath. 

Cool agar to 55 degrees Celsius before pouring plates to reduce condensation.

Step 5. Pour Agar

Prepare work space to pour plates using aseptic technique.  Mentally rehearse before removing the lid off the agar mixture to ensure that the work is done quickly and effectively. 

Stack petri dishes 5 plates high. Remove lid off agar mixture. Start by pouring the bottom plate on the stack by lifting its lid with the additional 4 empty plates. 

Repeat this action working up each stack without disturbing the already poured plates. Pour approximately 20 ml of agar into each plate. 

agar plates for mushroom growing

Step 6. Seal & Store

The cooled and set agar plates can be sealed using parafilm or plastic wrap. Unused plates can be refrigerated until use.

Today's Best Prices On Parafilm

Other Articles You May Like

Hello From Luke

Thank you for visiting! This website is user supported. As an Amazon associate I earn from qualifying purchases.


“Radical Mycology is a must for believers, and an end for non-believers. Peter McCoy indulges the reader into the depths of the mystical, spiritual, technical and practical aspects of all things fungal in one of the most elaborate mycological reads I’ve ever come across.” – Giuliana Furci

Popular Articles

Essential Articles

Sterile Media

Save time & money with pre-sterilised media for mushroom growing.