Preparation of Formvar Film-coated Grids
EMS Formvar Grids
|1% formvar solution in dichloroethane or formvar powder and 1,2-dichloroethane
|Film-casting apparatus (EMS 71305-01) or thistle tube with stopcock
||Plastic Petri dishes
|Dark bottom container
|Pie plate under bowl to catch runoff water
|Glass rod or lens paper to clean water surface
||Fine pointed tweezers
- Prepare 1% formvar in dichloroethane. Filter solution to remove impurities and keep dry. You can also purchase 1% formvar solution from major supply houses.
- Put formvar into film caster or container to use with thistle tube.
- Clean glass slides using distilled water and lens paper. Do not "over-clean" or films will not release from slides.
- Fill slide chamber* 3-4 cm deep with formvar. Keep covered as much as possible to minimize evaporation of dichloroethane.
- Put slide in chamber and let sit 2-3 min.
- Drain formvar from the chamber in a slow but steady stream.
- Let the slide sit in covered chamber for 2-3 minutes to dry. This gradual drying results in more even, thinner film.
- Remove slide from chamber and touch bottom to filter paper to remove any liquid formvar and complete drying.
- Scrape edges of slide and ~½ cm from bottom of slide with a razor blade to loosen film.
- Fill dark bottom container (large glass staining dish covered with electrical tape works well) with clean water and sweep surface with glass rod or lens paper to remove dust.
- Breath moist air onto slide and slowly lower slide into the water at ~45° angle to float off film. Have tweezers ready in case film needs a little help freeing from slide. Films should be silver in color. Gold is usually too thick and gray is too thin.
- Place grids onto the film with shiny or dull side down. Be consistent so that you always know which side has the film. Grids can be pressed down gently with round tipped glass rod if desired to ensure good contact.
- Lower a clean glass over the grids at ~45° angle and remove film plus grids with a steady but quick down and turn motion. (Note: parafilm or pieces of filter paper can also be used to pick up grids. Glass slides are cleaner and outgas less when put into carbon coater.)
- Remove excess water from the slide with Kimwipe or filter paper and place in filter paper lined Petri dish to dry.
- Slides with films are normally coated with carbon to provide additional support and conductivity to the films. The formvar film can be thinned after carbon coating by placing grids on filter paper saturated with dichloroethane for a few minutes.
- Films can be made by dipping slide into small jar of 0.2% formvar rather than using the film-caster method. These films usually are not as even in thickness.
1) Dip slides in formvar
2) Drain excess formvar from slide
3) Score along edges
4) Immerse in water to release film
Sherman, Debra. "Preparation of Formvar Film-coated Grids".DS Imaging, LLC. Web. 20 Mar 2014.