Hi all here from South Africa
I've had a few inquiries as to how I mold my fish so here goes.
I mold most of the fish that I get in with molding plaster, Dentstone, as I get maximum detail from this material.
Advantage of using plaster is that u can either use the fish after molding as a skinmount or u can make different molds from the fish without causing to much damage.
U can use this method for molding with Bondo or casting rubber as it works on the same principal. I would advise that beginners stay with plaster until they are experienced enough with molding before switching over to other methods.
First of u must make use of a good specimen and wash all the slime of the fish to get maximum detail. Also wash the inside of the mouth if u want to make an open mouth cast of the fish. The slime will definitely give u bad mouth detail when molding ur mouthplug.
I used a Nembwe as an example " bream species from the Okovango". I remove the fins as I will mold them separately.
Next we will start with the mouthplug. I mix a thin base of dental plaster, must not be to thick, just enough to fill the mouth cavity.
make sure that it is not to thick or thin otherwise u will get a detail problem. Fill the cavity with the plaster and wait for it to set up.
Next step is to clean around and outside of the mouth to get a smooth surface and to also get the maximum detail on the outside of the mouth. There are a few undercuts by the mouth that has to be cleaned. Make sure u do this before the plaster is fully set.
This picture shows the cleaned mouth.
The next step is to get ur molding box ready. U can use any type of molding bed like clay or sand. There are different ones that u can use, I use fine silica sand. U have to moisten it or u will get sand on ur fish. U don't want any pinholes in ur mold.
I cover the sand with a refusebag as not to get any sand on the fish and lay it in the box. Push the sand under the fish as to get the midline of the fish. U also at this time open the fins to the desired position before molding.
If u do get sand on the fish make sure that u clean it of with a brush. After u set the fish up make sure that the fish is dry. Use a cloth with thinners to remove most of the moisture on the scales. Be carefull not the dry the fins out completely as it will curl up and spoil ur mold.
Most other taxidermists spray the fish with a lacquer paint to get more detail, but I prefer the fish as is. I still want to get more molds from this fish and the paint will damage the fish.
Next step is to mix ur plaster. I use two different types of plaster.
I use the dental plaster for my splashcoat as u get the most detail from this. The other plaster is a normal white moldingplaster that is going to be my mothermold.
Make the splashcoat thin as to get maximum detail from the fish. As the plaster begins to set up, u can see this by taking the plaster in ur hand and let it drop back into the bucket making a small bump on top of the other plaster, pour it over ur fish making sure that all of the fish is covered. Start mixing the other plaster,it must be thick as to be spread over the first layer of plaster creating the outer shell on ur mold. Before the splashcoat has completely set u must spread the thicker plaster over it to get a good bond between the layers. If ur splashcoat has set u will have the problem of the outer shell cracking from the harder dental plaster and ur mold will be ruined.
Wait until the outer shell has set before turning ur fish around.
Remove ur mold from the box and smooth the sides of the plaster next to the body of the fish. U do this to get a smooth seam when u cast ur fish. Cover the sides of the plaster with a seperator. I use normal dishwashing liquid for this purpose.
Repeat the same steps as u did for the first side. Make sure that u clean the excess plaster of the sides otherwisw u gonna have a problem when splitting ur mold.
When the plaster has set up u can split the mold by tapping slowly on thre splitline. I use a knife for this. Remove the fish carefully as not to brake of the undercuts. The result is a very detailed mold that u can use for a pedistal mount.
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