Mounting presses are an excellent way to mount many specimens, and can be the most efficient and economical choice for many samples. However, the heat and pressure can cause significant damage to many samples – especially soft, porous or friable materials and coatings. In these cases, castable mounting systems must be used. Castable epoxy systems cure at atmospheric pressure. Their peak exotherms are typically lower than the temperatures used to make mounts in a mounting press. Specimens that are especially sensitive to heat should be mounted in epoxies formulated for lower peak exotherm, like EpoThin 2 and EpoxiCure 2.
Epoxies adhere to specimen edges and have low shrinkage. This means that they protect and support edges and preserve features, which allows both faster and higher quality preparation. For porous specimens, their low viscosity allows better infiltration into cracks and pores, especially when vacuum impregnation is used. EpoKwick FC and EpoThin 2 and provide the lowest viscosity available on the market.
Here are a few tips to make the most out of Buehler’s epoxy systems.
- Adding ‘Flat Edge Filler’ (hard ceramic filler) can further enhance edge retention and lower shrinkage. Keep in mind this increase the viscosity.
- Epoxies are very sensitive to the ratio of resin and hardener. It is usually recommended to mix by mass ratio than by weight.
- Warming the epoxy resin to around 30oC prior to mixing will further lower viscosity. This is helpful when vacuum impregnating small cracks and pores. This also can accelerate curing.
- The cure times for epoxies can be quite long. Some Buehler epoxies can be oven-cured to reduce cure times, although this increases peak exotherm temperature.