I need to prepare formvar-coated grids for TEM. I usually use an uncommon method of a drop of formvar on water, however the formvar film is usually uneven. Another and more common method is by using a glass slide, breath moist air and slowly lower slide into the water at ~45° angle to float off the film. Gold colour means the film is too thick, being the grey colour the best. However, I'm not getting the grey colour, and I get almost gold colour. I read that faster the lift of teh slide, the thicker the film will be. Is there any trick to get the grey colour. however i have tried to leave the slide 5 minutes in the formvar that...gold again!....anyone working in electron microscopy how that the grey colour is the COLOUR
Preparation of Formvar Film-coated Grids
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 about 0.5 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 around 45* angle and remove film plus grids with a steady but quick down and turn motion. 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.
Hope this info will help you
Good luck !!
Preparation of Formvar Film-coated Grids
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 about 0.5 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 around 45* angle and remove film plus grids with a steady but quick down and turn motion. 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.
Hope this info will help you
Good luck !!
Just some additions to the extensive procedure explained by Karen,
the time it takes for draining the chamber is really important. I usually use 1.1% Formvar in chloroform in a casting funnel with a drain time of 9 seconds. this produces nice silver films. 10-11 seconds will give grey films and 6-8 seconds yellow-golden films. Do keep min mind that the top part of the film will be a bit uneven because the flow of the solution hasn't stabilized yet.
good luck!
Rob
0.2% Formvar in dichloroethene, a droplet onto the water surface is the best method. I prefer it. There is a good old paper which closed the question about formvar film preparation:
Article Ultrathin Formvar Support Films for Transmission Electron Microscopy
E.g. negative stained T4 phage on such formvar film.
Good luck!
Dear colleagues,
Thank you all for your replies.
Karen A. Darbinyan , in did I'm using 1% formvar in dichloroethane.
Rob Mesman , I have seen in videos the draining chamber but I don't have one.
Denis Korneev after many tries, a droplet onto the water surface is, in fact, the best method for me. That you for the paper
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