The Epofix mixture is slow-curing and has a low viscosity (550 cP at 20° C, 150 cP at 50° C) (Anonymous 1995), making the mixture particularly suited for vacuum impregnation. Although Epofix resin and hardener are both soluble in alcohol and acetone, these solvents should not be used to reduce viscosity (Electron Microscopy Sciences, personal commun., 1999). Instead, the Epofix mixture may be heated a little before application (max. 40°C). It was not done in the examples above. As the linear hardening shrinkage is insignificant or not existing (Anonymous 1995) it produces reliable results suitable for quantitative studies. The sectioning properties of Epofix mixture are good. A comparison with other embedding media is beyond the scope of this paper. The reader is referred to Bromage (1985), who provided a systematic evaluating procedure for casts and moulds.
The procedure described here produces adequately impregnated hard-substrate samples for studying macroscopic and microscopic scale bioerosion structures (Figure 1, Figure 3, and Figure 4). It is essential that the bioerosion structures are empty or that their fill is removed. Otherwise, the cast agent cannot enter and fill the bioerosion structures (e.g., Ekdale et al. 1984). Therefore, our procedure is not suitable for casting recent borings containing organic matter, e.g., remains of tracemarkers. Sodium hypoclorite, better known as commercial Clorox, may remove the organic matter. It should be kept in mind that excessive use of Clorox has a corrosive effect on molluscan organic matter, can alter the ultrastructure of the shell surface (Carriker 1979), and may affect bioerosion structures. This is important since relationships between microbioerosion and shell architecture may exist (e.g., Golubic et al. 1975).
The cold mounting within our procedure is particularly appropriate for heat or pressure sensitive samples (i.e., shell material to study microstructures, ultrastructures, and chemistry). Consequently, the procedure seems better than earlier suggested ones, which required warm curing for 40-72 hours.
Due to the cost of an Epofix kit (about US$ 100) a small amount as possible is used. To lower the amount of Epofix used, apply aluminum foil to casting containers. Foil, with a greasy internal surface, can be shaped to fit a given sample. The grease makes it possible to separate the hardened Epofix and the foil. The container may be stabilized by placing in a box with sand (H. Lindgård, personal commun., 1999).
The aging properties of Epofix are promising, that is minimal yellowing over time with nominal shrinking. This is concordant with our observations during the last three years, which include SEM re-examination of casts containing preserved remains of shells. Hence, it follows that the casts are suitable for long-term use.