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The Lost Wax Casting Process
Wax: An Overview
Ceramic Slurry Dipping Schedule
The Sandcasting Process
The Chasing Process
Methods for Joining Bronze
Patinas
Investment Casting: 1930-1950
Project #2: Sandcasting a Bas Relief Bronze Plaque
How to Build a Bronze Casting Furnace
Foundry Safety
Furnace Lighting Procedure
Project #1: Direct Wax Sculpture, Ceramic Shell Casting

Project #2: Sandcasting a Bas Relief Bronze Plaque

This is the 2nd project I assign my students. It is a simple bronze bas relief plaque. The pattern, or original plaque is made using sculpey spread on a masonite or plywood. This is a sandcast piece using petro-bond.

I'm including this in my articles because it gives a step-by-step overview of the process, inculding pictures.

Project #2 Sand Casting a Bronze bas relief Plaque

Bas relief (bah’ruh-leef) – A French term that means “low-raised work.” This art, combined with “high relief” is known as relief sculpture. It is meant to be viewed from one direction as opposed to sculpture meant to be viewed in the round.

ASSIGNMENT: Create a bas relief consisting of a montage of images that represent a dream or emotional experience. The bas relief will then be cast in bronze using the green sand casting method.

Purpose of Assignment: Understand the process of sand casting, including its limitations and advantages. Have the opportunity to pour your own bronze piece. Further, investigate the techniques learned in project #1 (chasing, finishing, patination).

Grading: Pieces will be critiqued and discussed, emphasizing technique and finish, rather then concept and design. Grades will be based on 75% design, technique and finish that execution of the design n the plaque, quality of the casting, metal finish, patination, presentation; 25% of the grade will be on concept and creativity.

 

Supplies:

• 1 lb sculpey (or super sculpey)
• Spray Shellac or lacquer
• Various clay working tools

• One 5” x 5” x 1/4” thick wood backing (plywood or masonite) with the edges cut at a 30° angle.

 

Project Sequence:

You will be given a 1/4” thick wooden plaque measuring 5” square with the sides cut at an angle. This leaves a surface area of 4.75” square for your relief. This board will be the backing for your bas-relief.

1. Create a picture or collage measuring 4.75” square that represents a dream or emotional experience.

2. Score the front of the wooden board with a screwdriver or sharp metal tool to roughen it up.

3. Take small dabs of sculpey and smear them onto the roughened front of the board until there is an even coat on it, then build up the coat to about 1/8” thick. Smooth the surface of the sculpey flat. (fig. 1)

4. Attach the picture you have made on the front of the board with a few pieces of tape. With a small nail or wire, punch holes along the lines to transfer your picture onto the sculpey. (fig. 2, 3)

5. Add or subtract sculpey to form your bas relief (this is the sculpting part). (fig. 4, 5)

6. When finished bake the plaque following the instructions on the box of sculpey. Include the thickness of the board when calculating thickness. (fig. 6)

7. Once cool the sculpey will be hard. If you want, you can do some finishing work with small handmade chisels, sandpaper, an Exacto knife or small files to refine the relief. (fig. 7)

8. Check that there are no undercuts by pushing the plaque into Petrobond and then lifting it out. It should leave a clean impression and have no sand stuck to it. (fig. 8, 9 – here sand is stuck to the relief after lifting it up).

9. If there are undercuts, they can be fixed by filling them with hard wax with a hot knife, then carving it back.

10. Spray 3 coats of lacquer onto the relief, make sure it drys completely! The back should receive one coat.

11. Sandcast the relief as demonstrated in class. See fig. 10, 11 for gating diagrams.

12. Remove sprues and vents.

13. Chase and finish.

14. Patina.

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Fig. 1: The board with sculpey smoothed on.

Fig. 2: A picture taped onto the plaque.

Fig. 3 Tracing the design by punching holes in the lines.

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Fig. 4: Sculpting the design.

Fig. 5: Carefully sculpting the letters. Be careful to leave a draft so the sand mold releases easily.

Fig. 6: The baked plaque is now hard and can be finished. Rather then working like soft clay, the material can be sanded, filed, or scraped. Small chisels and handmade tools are used to round inside edges, smooth area, etc.

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Fig. 7: The mold is pressed into petrobond sand to see if it has any undercuts or areas that are too deep. In this case there are several.

Fig. 8: Sand caught in the face area. Once the sand is removed, the area is built up with wax using a hot knife. Once cool the wax is recarved to correct the problem.

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Fig. 9: On the left is the fixed plaque. Red casting wax was used to correct the flaws. On the right is the finished bronze plaque.

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Fig. 10: GATING FOR PLAQUE - SIDE VIEW: The plaque is on the right with vents on top of it. The dotted line is the parting line. We use flasks made from 2x2's, and this does not allow very much head pressure - when we cast we put a brick under one side of the flask to allow gravity to add a bit more pressure.

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Fig. 11: GATAING FOR PLAQUE - TOP VIEW

For a further discussion on sandcasting, see my article on the Sandcasting Process.

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Dan@RotblattSculpture.com
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