Continuing on where we left off last time, this post will attempt to cover how we make a protective support jacket for very large or heavy specimens.
For really weighty specimens, like our dinosaur’s limb bones, we create a sort of supportive shell for the bone from a substance called Epopast, an epoxy resin/glass fibre paste. Epopast is pretty nasty stuff so to mix up a batch we need to get kitted out in full PPE (personal protective equipment)- goggles, mask, lab coat, apron, gloves and gauntlets (arm guards).
First things first, though- the bone must be protected before we go covering it with chemical goo. We cover the whole top surface with Clingfilm. The next step is important- any uneven areas where the Epopast might creep under must be filled out with plasticine, or the hardened jacket might be impossible to remove!
After carefully mixing the correct ratio of Epopast fibres with the goopy green hardener chemical, paying particular attention to the alarming hazard labels all over the containers, the mixture must be kneaded together vigorously to produce a doughy green pliable substance not unlike playdough and smelling faintly like biscuits. We take small handfuls of this stuff, shaping it into patties and applying them to the covered bone’s surface, gradually creating a layer over the whole top half of the specimen. Once the Epopast layer is in place, the finishing touch is to cover it over with another layer of Clingfilm (once patted down, this should ensure that no razor-sharp strands of hardened glassy resin are sticking up ready to stab unsuspecting fingers). Then we’ll leave it to harden for a few days. Once it’s fully set, we can then flip the bone over and begin the whole process again on the other side. Finally, the hardened Epopast jacket halves must also be smoothed down with an abrasive tool.