Do you re-use petri-dishes? I hate the idea of buying sterilised plastic dishes and using them just once. I want to fill (and ideally re-fill) the dishes and then sterilise them. I found PP5 sauce containers (about 50ml zsize) useful for that. I think the higher wall to bottom surface ratio (taller shape factor) allow for some bubbling while it's in the pressure cooker, while standard petri-dishes probably boil over, stick together, and end up with continuous agar-bridges to the outside for contamination to get in.
Oh Zap!
This is what a spore syringe looks like after it has germinated on a petri dish. You can see that there are a large number of distinct colonies which are all competing against one another.
http://lightningspore.com/wp-content/uploads/2024/02/spore-germ-zap-1-scaled.webp
You have a lot of options to choose from here (I had about 3 plates which looked like this). What I do next is then use a scalpel to extract the edges of clean and vigorous looking colonies and move them to another dish to grow out further. We call this the T1 generation. In order to save time and plates I did 3 transfers to each new plate. Starting at the T2 generation, I will only do a single transfer to each plate.
http://lightningspore.com/wp-content/uploads/2024/02/spore-germ-zap-2-scaled.webp
Someone sung to me to praises of the WEBP image format, so I've started to upload all my images in that format (500kB vs 5MB for these images). Let me know if you cannot see the images.
Discussion
I have some glass dishes I’ve used a bit. But it sucks how heavy they are. PP5 sauce and takeout dishes can work for reusable. But it takes a lot more time and effort than the pre-sterilized ones. I can buy 500 of them for pretty cheap. At the moment I’m optimizing for efficient use of my time.