Banana Candles Made with Plaster and 3D Printing

Introduction

This guide details how to create a unique banana-shaped candle holder using 3D printing for molds and plaster for the casting. The project involves creating a two-part item: a candle and a plaster base. The 3D printed mold can be reused to create more candles.

The process includes using the MOLD setting in CURA for 3D printing molds and casting plaster into these molds.

Supplies

• 3D Printer ?️
• Plaster of Paris/Gypsum/Cement (Optional) ?
• Candle Wax, Wicks ?️
• Sanding Paper, Scalpel, Filler/Putty, Disposable Gloves ?
• Brushes, Acrylic Paints, Tough Exterior Varnish ?

Step 1: Banana Candle Model

The process begins by using a base model for the banana shape, found on Thingiverse (thing:3664845). This model was tweaked to thicken the peeled sides and add an exposed banana part. The candle part is designed to fit seamlessly within the plaster part.

Tinkercad model link: Banana Candle Model

Visual Description: A 3D model of a banana, split into two parts: a top section for the candle and a bottom section for the plaster holder.

Step 2: Lower Banana Model

This step involves the 3D model for the lower part of the banana, which will be cast in plaster.

Tinkercad model link: Lower Banana Model

Visual Description: A 3D model of the base or holder part of the banana candle.

Step 3: Lower Banana Part - PLA Covered in Plaster

This part is printed in PLA and then processed with sanding, filler, paint, and varnish.

The author experimented with covering the PLA print with a layer of plaster to achieve a rough texture. After printing the PLA part (with settings like 0.3mm layer height, 15% infill, 3 walls), it was covered in a thin layer of plaster. The PLA surface was first roughened with 40-grit sandpaper. Plaster of Paris was mixed to a heavy cream consistency and applied with a disposable brush. After drying, it was sanded, and a second layer was applied and sanded again.

Visual Description: A green 3D printed banana part partially covered in white plaster, with plaster dust scattered around.

Step 4: Lower Banana Part - Plaster Cast (Mold Creation)

This step focuses on using CURA's "MOLD" setting to create molds for plaster casting.

CURA has a specific "MOLD" setting that can be used to print objects designed to be molds. To access it, go to settings in CURA and type "MOLD".

Tips for Printing Molds:

• Printing in mold setting takes approximately twice as long as normal printing.
• Print with thin walls: 1-2 walls, or preferably a single wall.
• An infill between 5% and 15% is required; printing without infill will result in a flimsy mold that may bulge under the weight of the plaster.
• Pay attention to retraction settings to avoid stringy bits inside the mold.
• Certain shapes may require supports, which need careful monitoring to ensure they do not print inside the mold where they would be difficult to remove.

Visual Description: A screenshot of the CURA slicer software showing the 3D model of the banana part on the build plate. Another screenshot shows the print setup panel with various settings like Shell, Infill, and Speed. Text annotations highlight recommended settings for wall thickness (0.4mm or one layer), infill (5-15%), and the importance of retraction settings to avoid stringy bits inside the mold. A third screenshot shows the model with supports generated, and text annotations emphasize experimenting with supports to ensure they don't obstruct the mold cavity.

Step 5: Lower Banana Part - Plaster Cast (Casting and Demolding)

This step covers casting plaster into the 3D printed mold and then removing the mold.

After printing the mold, inspect its interior for holes or stringy bits. Clean as necessary and fill any holes with filler or putty if the print quality is poor.

Casting Process:

• Mix plaster (or cement) with water to the desired consistency and pour it into the mold.
• For small, tight areas, a piping bag with a short plastic straw tip can be used to pour plaster precisely.
• Allow the plaster to set and cure for several days. It is crucial for the plaster to be fully cured, not just set, to prevent cracking during demolding.

Demolding Process:

• Once cured, use tools (some may be makeshift) to remove the plastic mold.
• A Dremel can be used to cut through the first wall of plastic, and then a small tool can peel away the inner wall.
• A link to potential tools is provided: Rolson Wax Carver Set.
• After removing the mold, sand the plaster.

Visual Description: Images show the process of plaster casting. One shows a green PLA banana mold part being prepared. Another shows a piping bag filled with plaster, ready to be applied. Subsequent images depict the plaster cast banana part with the green PLA mold being carefully removed, showing fragments of the plastic mold. Tools like a Dremel and scalpels are visible. The final image in this step shows a white plaster cast banana part, partially freed from the green plastic mold.

Step 6: Painting

Decorate the lower plaster part of the banana using acrylic paints or spray paints. The author chose strong colors inspired by pop art.

Visual Description: A finished plaster banana holder, painted in bold colors (e.g., gold and black, or pink), with a yellow candle inserted.

Step 7: Candle Part (Mold Printing)

This step involves printing the mold for the candle part. The mold is designed with keys for easy interlocking and elongated edges, allowing paper clamps to hold it together.

Tinkercad model link: Candle Part Mold

Visual Description: A 3D model of the mold for the candle part of the banana.

Step 8: Candle Mould Preparation

This step details the preparation of the candle mold before pouring wax.

• If the inside of the mold has a rough texture, apply a layer of tough, outdoor varnish to ensure a smooth finish for the candle.
• Assemble the two halves of the mold using paper clamps to hold them together securely.
• Use a hot glue gun to temporarily attach the wick to the top of the mold. Apply extra glue around the top edges to prevent wax from seeping out.
• Secure the wick in a straight position using hot glue and toothpicks.

Visual Description: Images show the green PLA candle mold halves clamped together. One image shows a hand applying varnish to the inside of a mold half with a brush. Another shows the assembled mold with a wick secured by hot glue and toothpicks.

Step 9: Candle Wax Pouring

This step covers melting the wax and pouring it into the prepared candle mold.

• Melt yellow candle wax and cool it to approximately 65-70°C.
• Pour the melted wax into the candle molds and allow it to cool down completely.
• Once the wax has solidified, unmold the candle. Use a scalpel to trim any excess edges if necessary.
• Place the finished candle into the plaster base.

Visual Description: Images show the green and white PLA candle molds, clamped and ready. Yellow wax is shown being poured into the molds. Later images show the finished yellow banana-shaped candles removed from their molds, with some wax drips.

Step 10: Finished Product

The project is now complete. You have created a unique banana candle holder with a 3D printed and plaster-cast base and a handmade wax candle.

Visual Description: Images showcase the final product: a yellow banana candle inserted into a plaster holder that is painted in various colors (e.g., gold and black, or pink).