HOW TO COAT GRIDS
You should bring:
We will provide:
3. Formvar solution (0.5% in Ethylene dichloride)
4. Microscope slides
5. Pressurized air can
6. Drying chamber for slides
7. Water dish
8. Light source
9. Rubber grid mat
10. Razor blades
11. Cover slips and Parafilm
12. Plastic petri dish with filter paper
1. Clean slide using the twill cloth. The slide will feel
``sticky'' at first, but then should feel smooth. Look for
lint on the slide, if present use the air can to remove.
2. Dip slide once into formvar solution, tapping it gently once or
twice on the bottom to dislodge air bubbles.
3. Bring wet slide out of the solution, but keep it in the jar in
the vapors above the liquid for about 30 seconds. Hold the jar
lid over the top to help maintain a saturated vapor phase.
4. Quickly place the slide in the drying chamber, cover, and let dry
for at least 5 minutes, but no longer than 30 minutes.
5. Clean grids by placing them in a microfuge tube with Acetone.
Shake vigorously, then place them on filter paper in a petri
dish to dry.
6. Check the surface of the water in the dish. If dirty, clean by
dragging a Kimwipe over the surface. If the water is extremely
dirty (grids on the bottom, etc.) pour out the water into the sink
and dry the dish using a large Kimwipe. Check for lint in the dish
and remove using the air can, if present. Add fresh distilled
7. Remove dried slide from drying chamber, use razor blade to gently
score end and sides. Too much pressure causes the glass to chip
and the chips get on the film.
8. Breathe on slide so that it fogs up, and as soon as it clears,
hold slide away from you perpendicular to the water. Lower the
slide slowly into the water and watch for the film to come off onto
the water surface. As you lower the slide into the water, the
Formvar film should be silvery to silvery-gray. If it is gold colored,
it is too thick. If it is gray to black, it is too thin. If all
films are either too thick or too thin, the you will need to use
fresh Formvar solution.
9. Place grids on rubber grid mat, and use forceps to pick up and
transfer to film on water. If grids have a shiny and dull (dark
and bright) surface, place the shiny (dark) side against the film.
Grids can be placed quite close together-usually 5 across the
short dimension of the film.
10. Picking up the filmed grids:
Coverslip method- Choose a coverslip that is longer than your
film. Clean the coverslip if necessary. Hold the coverslip by the
edges and slowly lower it so that it touches the edge of the film.
Continue submerging the coverslip until all of the film completely
contacts the coverslip. Pull the coverslip straight up, let the excess
water drain. Place coverslip into petri dish with filter paper
(grid side up), cover with lid askew and let dry.
Parafilm method- Cut a piece of Parafilm slightly larger than
your film to pick up the grids. Holding the Parafilm with clean
forceps (you don't want to dip your fingers in the water), come down
from the top at an angle, touch one end of the film/grids, then
lower Parafilm so that all of the surface of the formvar film is
touching the Parafilm. Lift up the Parafilm/grids and set aside to
dry in a petri dish with the lid askew to allow air flow.
11. Once the grids are dry, carbon coat and glow discharge them (if
necessary) using the vacuum evaporator.
12. When not sectioning store the grids in the refrigerator in the
petri dish. Label and date your petri dish.