Summary
Highlights
The initial curing phase involves pieces that are freshly impregnated and exude a lot of the impregnation mixture. It is crucial to dry the surface of these specimens, such as dog brains, to prevent the formation of a crust when they come into contact with the crosslinker vapor (S6). This drying must be repeated multiple times on the first day as exudation is continuous. Using paper on the grids can prevent pieces from sticking.
After drying the surface, other elements are introduced into the chamber to start curing. These include silica gel as a desiccant and a flask with S6 liquid. An aquarium pump is connected to bubble the S6. It's important not to directly inhale the vapor from the S6. The chamber is then closed, and the S6 bubbling is allowed for 10-15 minutes to saturate the chamber. After this, the vaporization can be turned off, and the vapor is allowed to act for an hour or two before repeating the process of drying the surfaces and reconnecting the S6 bubbling.
After a few days, the pieces begin to polymerize. The silicone mixture on the surface becomes more viscous, requiring careful and repeated cleaning. It's important at this stage to fix the position of structures using needles, as they will remain in that position permanently after polymerization. For pieces in a medium curing phase, the highly viscous polymer on the surface requires this cleaning operation to be repeated multiple times daily and over several successive days.
In more advanced stages, very little polymer mixture is left on the surface, and what remains is very viscous. Continued careful cleaning is essential to prevent crust formation. During this process, dissection maneuvers can be performed on the pieces, such as opening a ventricle in a heart to visualize internal structures like papillary muscles and valves. This allows for careful internal drying and ensures both internal and external curing of the specimen.
Curing occurs from the surface inwards. A piece is considered fully cured when no more polymer mixture appears on the surface after several days. The final stabilization step takes place outside the curing chamber. Once a piece has stopped exuding polymer for several days, even after being in the chamber, it is placed in a sealed plastic bag without S6. The S6 continues to act progressively from the surface inward, achieving full polymerization over weeks or even months.
Pieces can be in different curing phases, with varying levels of silicone exudation. The key to preventing total polymerization on the surface is continuous drying with absorbent paper. The curing process is controllable and can be adapted to work schedules. To stop curing overnight, pieces can be removed from the chamber, wrapped in paper, and frozen. This halts the polymerization reaction, allowing the process to resume the next day after the pieces have thawed and been cleaned.