Preparing Resin Parts For Painting
All the 1/72 scale diorama kits, accessories, etc. sold under the Full Circle Hobbies name are cast in polyurethane resin. Resin is a type of plastic used for low volume production of parts and possesses some very different procedures for preparation and assembly compared to plastic.
The first step in the preparation of resin parts, is to sand off any parting lines and / or pour plugs.Soak them for 45 minutes in warm soapy water, then wash the parts thoroughly under warm running water. Common dish soap is good for this because it will easily remove the greasy mold release film from the parts caused by the casting process. In the past, resin casters had to use a mold release agent that left a heavy oily coating on the cast parts, but now most manufactures including myself, use silicone self - releasing molds that leave parts clean. It's still a good idea to wash the parts just to make sure your paint will stick. If you don't wash the parts properly from some manufactures, paint will not stay on them.
Unlike the styrene plastic used in the typical model kit, resin is impervious to most solvents and paint thinners. Just about any type of paint or primer, automotive, home, or hobby paint, either lacquer, enamel or acrylic, can be used on resin without fear of crazing the surface. Use white or grey primer for figures, and flat (matt) black for dioramas, buildings, and vehicles because it also acts as a pre-shade.
On some of my large diorama parts there's a thin lip around the casting. This is a sanding guide. Tape a large piece of 80 grit, or coarser, sanding paper to a flat surface and place the part on it. Sand slowly in a circular motion until the guide is paper thin or sanded off completely. A darker primer coat makes this process easier to see. I strongly recommend using a dust mask while sanding resin, as the fine dust created is very irritating if inhaled.
Once the parts have been sanded and parting lines and / or pour plugs have been removed, you might need to fill some casting imperfections or small air bubbles. These imperfections can be filled with automotive spot putty which comes pre-mixed in a tube.
Once all of the imperfections have been filled and re-primered, it's time to glue the parts together. Sand or scrape the primer off any mating surfaces before gluing them to ensure a strong bond. The best glues for bonding resin to resin or resin to other types of materials, is 5 minute epoxy or CA glue. Regular glues made for plastics will not bond resin.
After all of the above has been done, you can now move onto the most fun part of model building, painting and adding details. For information on painting models, read my series of articles on this site. You'll find them very helpful.
I hope this information helps you with preparing resin kits for painting. If you have any questions or comments regarding my products, please don't hesitate to contact me at email@example.com.
Happy model building!
Owner of Full Circle Hobbies