While those specializing in electron microscopy might know of Formvar only
as a superb grid support film,
there are other important applications for Formvar resin, which has
applications in a wide range of different areas, including wire coatings,
magnetic tapes and adhesives.|
While it is hard to prove, the general perception is that Formvar is a
bit stronger than the other support film materials, enabling one to use
grids with lower mesh rating (larger grid squares) than with other
support films. On the other hand, another perception is that the
ability of the film to withstand heating effects is not as good as for
Formvar can be dissolved in a variety of solvents with ethylene dichloride
and chloroform being the two most popular. Another solvent is dioxane.
Formvar in solid form is not hazardous where as when dissolved in a solvent,
the product becomes flammable and therefore hazardous, meaning it is more
expensive to ship, unless ordered in the
form. If you have not made filmed grids previously, then you might want
take some of the advice from the
master grid coaters at SPI. Or if this all sounds like too complicated
of an exercise and you just want to get on with your research work (and not
become a master grid coater yourself), then
consider having SPI make the filmed grids for you.
Additional information about solubilities can be found elsewhere on this
Lower vapor pressure solvents:
We have been told that when one requires a solvent that evaporates more
slowly, one possibility is N,N-dimethylformamide. We know that this is an
even more nasty kind of chemical than the alternatives, but we thought this
information, for some, might be useful.
One needs patience to dissolve Formvar. It can take days, not hours, to get Formvar resin
into solution. That is why the purchase of the ready-made solutions is often times preferred
because of the inconvenience of doing one's own dissolution.
In order to provide the highest quality Formvar resin products, the solid
form is packaged under dry conditions and the solutions are in "ready-to-use"
form. Just remember that the making of high quality TEM grid support films
is truly an "art" and does take most people some amount of time to learn.
Therefore, once you have decided to do your own grid coating, then take
advantage of some of the tips from
the SPI grid coating experts! They will also share with you some of their best
held secrets for the production of outstanding lacey
carbon or lacey Formvar coated grids. Or if you would rather short circuit the time otherwise
needed to look at your important samples, consider the purchase of
grids already custom coated by SPI Supplies.
Note of caution:
If you are new to your laboratory and have a bottle labelled as "Formvar",
remember that unless it is the special grade of Formvar optimized for the
making of support films, quite likely, the resin will not produce the kind
of result expected. Furthermore, if the resin has aged beyond a certain
(but unknown) point, there are indications that changes could have occurred,
perhaps due to UV, and one should considered discarding the old resin and
starting over with fresh materials. Fortunately, the Formvar resin is one
of the lowest priced items one is likely to be purchasing for their EM