SPI Supplies Brand Formvar Coated 2270G SPI Asbestos Index Grids, Gold, 200 Mesh, Pack of 25
The pattern familiar to many, the SPI Asbestos Index Grid, is now available as a standard product, with all of the commonly asked-for grid coatings (support films).
Originally conceived by our own analysts doing TEM asbestos work, we realized the importance of not only having a good and easy-to-use "finder" or "index" grid, but it was also important that each grid square have the same, precisely controlled, open area. Other index grids did not have this feature. And we also knew that for verification counting (one person checking someone else's measurements), it was also important to be able to put the grid back into the TEM at precisely the same orientation as it was inserted the first time by the first analyst.
So you don't have to be doing asbestos work in order to benefit from these out-of-the-ordinary TEM grids. Anyone interested in doing quantitative measurements where the area per grid square must be within a very tight specification, would find these grids to be their grids of choice.
For anyone planning to make quantitative dimensional measurements:
An often overlooked feature of anyone doing TEM work on conventional grids if the phenomenon of "grid sag". This refers to the "sag" of a fragile thin film as it is literally "strung" across a grid square, from grid bar to grid bar. And since the magnification will depend on location within the objective lens, there is a magnification variation from point to point on the typical section, which will of course exhibit some (unknown and immeasurable) amount of "sag". Should this ring some "bells" about your own work and your own samples, then the solution is the unique SPI Supplies Brand of silicon nitride membrane window grids, where there is no sag whatsoever.