There are two distinct uses for holey carbon grids: for image checking and for support for ultrathin carbon films for cryo- EM. This procedure gives holes that are too large for convenient image checking, but are the appropriate size for support of carbon films. The procedure is divided into making the formvar mixture, dipping the slides and getting the film on the grids.

1) Take 45 mL of chloroform, add 0.2 g of formvar, and shake to dissolve. A small brawn glass jar with a capacity of 100 mL is the best container to use, and the jars from commercial formvar solution are ideal.