During long experiments, with many incubation steps in different solutions, sections may detach from the slides. To prevent lossing sections, slides are coated with adhesive substances that keep sections attached. One of the cheaper and easy to prepare adhesive solution is that containing gelatin and chrome alum.
1) Add 200 ml of distilled water in a beaker and rise the temperature up to 60 ºC in a heater-stirrer. Add a magnetic stirrer bar.
2) Add and dissolve 1 g of gelatin.
3) Add and dissolve 0.1 g of chrome alum. The solution turns pale bluish.
Chrome alum provides positive electric charges to the surface of the slide. The sections remain attached to these positive charges because tissues have a net negative charge.
4) Pour the solution in a staining dish preheated at 60 ºC.
5) Dip the slides 3 to 5 times in the solution, 5 to 10 seconds each.
6) Leave the slides to drain for a few minutes onto a filter paper. Slides can be gently agitated for a better draining.
7) Dry the treated slides in an oven at 37 ºC for 16-24 hours.
8) Store the slides in a dry box and protect them from dust.
The slides have to be clean and degreased.
The gelatin solution can be stored at 4-8 ºC for several days. Before each treatment, it should be checked the solution is transparent. Then the solution is tempered and filtered.
A few drops of timol can be added to longer preserve the gelatin solution.
When many slides are going to be treated, the slides can be warm up before dipping into the gelatin solution to prevent the lowering of temperature.
Chrome alum (CrK(SO4)2 · 12H2O)
Magnetic stirring bar