In September, 2010, I volunteered to build a float for a Halloween parade. The theme of the float was patriotic / historical, incorporating historical US flags and a replica of the Liberty Bell. For some time I had wanted to experiment with sculpting with extruded polystyrene (XPS) foam, so this project afforded the oppurtunity to consume scraps of 2" material had saved from my insulating-the-workshop project. At the time I built the replica, I wanted to encase it in fiberglass-reinforced polyester (FRP), but time did not permit. That had to wait until later.
I knew that I could deal with the vulnerable nature of the paper maché and joint compound exterior skin for one parade event. Unfortunately, over the subsequent months, handling and storage of the bell revealed that refinishing with FRP would be necessary and inevitable if I were to keep the bell useful. When I finally found the time to do this, it did not occur to me to take photos of the process. This was partially due to my fear of the resin setting before I was finished working with it (I generally don’t have an assistant). I also did not document making the crown, mounting hardware, yolk, supporting frame, and road case.
Step 1: Materials and Tools
1. Utility knife
2. Wood file/rasp
3. Small hand saw
4. Bar compass
5. Metal straight edges/rulers
1. White glue (I prefer Elmer's)
2. Rubber cement
3. Spray adhesive (I prefer 3M 77)
4. Gorilla glue
5. Paint brush (I used 1”)
6. Putty knife (I used a 3” taping knife)
7. 2” Extruded Polystyrene
8. Poster board or equivalent (I used the discarded backs from tablets and legal pads)
9. Large paper (I used the reversed side of discarded engineering plans)
11. Joint compound
13. Sanding sponge
14. Spray primer
15. Spray paint (I used Rust Oleum Hammered, Copper)
Note: Selection of adhesive is critical when working with plastics such as XPS, since styrene is soluble in several petroleum distillates, such as acetone. XPS does not appear to be damaged by 3M 77, but is dissolved by 3M 90 and petroleum-based contact cement. Additionally, petroleum-based spray paint can soften XPS and polyester resin attacks it quite aggressively.