I have a nice slide that I got from GE when they were giving an OMX demo about hardening vs non-hardening (#8 in the following presentation):
Feel free to use it as long as you attribute the person from GE that gave it to me.
The only thing I don’t like about that slide is that it doesn’t have a side view of what Prolong-Gold/Diamond looks like when you seal a coverslip with nail polish immediately after mounting (ignoring what the manual says). This keeps the Prolong from drying and squishing the sample, as well as the RI from going up. Despite the mismatch in RI and the concomitant spherical aberrations deeper in, we find that it is better to not flatten the sample for anyone interested in imaging in 3D. If you don’t care about 3D structure, flattening the sample is great for widefield. So, what we recommend if using a hardening media like Prolong is seal immediately if you are doing confocal, let cure if you are doing widefield.
What my users would really like is a commercial product that does not harden, has good antifade properties and a high RI (matched to the 1.518 of typical Big 4 oils). Or, something homebrew that is cheap and easy to make, with the same characteristics. Some clearing solutions like TDE or SeeDB2 variants would fit the bill, but I don’t have a good idea of the cost or hassle level involved in making them.