How To Use Parafilm
This is what we are going to be using:
Why Use Parafilm?
Parafilm is fantastic stuff (you can buy it here). It is a film that you can use to seal up your petri dishes that prevents any nasties from getting in while remaining breathable. After working hard to keep your agar work free of contaminants the last thing you want is for something to get in there and ruin it.
Time To Use Your Parafilm
First of all you need to cut your parafilm to the required size. It has been conveniently marked out so you just have to follow the blue lines. We are going to go two squares across like so:
First of all I like to take the film, remove the backing, and fold it in half along the long edge like this:
Now we are ready to take our petri dish and start wrapping the film around. Be concious of what you have inside your dish as you probably want to keep the dish flat while wrapping it up so the contents don’t go everywhere. The film stretches so if you start by pinning the end down with your left thumb you can pinch it with the thumb and forefinger of your other hand so the tips of your thumbs are touching, and then pull it about 3-4cm while wrapping it around the agar plate. You can definitely over stretch it and it will snap so err on the side of caution. Stretch, attach, stretch, attach, going all the way around the rim of your agar plate. Think of it like stretchy clingfilm.
Once you get all the way around there is usually a small overlap which is ideal for making sure the dish is completely sealed and also indicates you are stretching the parafilm the right amount. If your sealing them up to be used later they last about 1 month. You can also keep them in the fridge which i’m sure will extend this time frame significantly.
And that’s all there is to it.