The general process of making a fossil model is as follows:
(1) Selection of replication materials. In 1960s and 1970s, gypsum, as a kind of reproduction material, was widely used in museums all over the world, with low cost, simple manufacturing process and easy operation. But after 1980s, unsaturated polyester resin (also called "glass fiber reinforced plastic") gradually replaced gypsum. Its advantages are high strength and light weight, and it is suitable for mobile exhibitions, but the operation process is complicated. In recent years, gypsum and glass fiber reinforced plastic materials are usually combined.
(2) making the outer membrane. There are two kinds of plaster mold replication: one is disposable mold, also known as dead mold; The other is the reusable outer mold, also known as the movable mold. Before copying, the specimen is coated with isolation agent, and then divided into several pieces according to the shape of the object, and copied one by one. The operation of copying the silicone rubber outer mold is simple. The specific steps are to brush silicone rubber on the original and brush it repeatedly. In order to increase its strength, a layer of gauze can be added after brushing twice to make the thickness of the mold reach 5 mm, and then the gypsum mold is turned over on the silicone rubber outer mold to fix the silicone rubber in the gypsum mold. This plaster mold is called a molding mold. Then take out the real thing and cast a replica.
(3) Reproduction of fossil materials. Apply release agent on the inside of the turned outer mold, close the outer mold and tie it tightly, leaving the pouring port. For large-scale fragile replicas such as leg bones and ribs, steel bars, wood squares and other materials should be put into the mold before closing the mold, and then cast. In order to increase the strength of gypsum, a small amount of cement can be added appropriately. When mixing gypsum, appropriate colors can be added as needed to lay the foundation for future coloring. After the gypsum is completely solidified, remove the external mold. Finally, the casting port and other parts were rebuilt to make them the same as before. For the reproduction of smaller fossil specimens, the method of partial one-time casting of gypsum can be adopted. Turn over the larger vertebral body, leg bones, skull and other bones, and then combine all the parts.
(4) Coloring (Figure 3-3). Because there are essential differences between copied fossil specimens and restored fossil specimens, it is necessary to color the copied ones. Generally, replicas of FRP use mineral pigments, and pigment flakes are used as blending agents. Replicas of gypsum can also be painted with advertising colors. Mixed pigments should be painted by spraying, spotting and blasting, and the color tone should be consistent with that of the original fossils, and the background color should be painted first and then colored one by one. The reproduced fossil specimens can be displayed separately or in combination, which is also an indispensable part of the auxiliary exhibits.
Figure 3-3 Color the restored model (photography/lofty)