How to Make Silicone Molds

Comprehensive Guide to Creating Silicone Molds

There are two primary methods for creating molds from liquid silicone rubber: brushing and pouring, with the choice depending on the size and complexity of the product’s design.

Pouring Silicone are suitable for small and large flat products with neat and simple pattern, which is conducive to the liquid silicone being able to level itself well. Brushing Silicone is suitable for products with fine patterns and complex structures.

Here are the main points and operational details of brushing and pouring the silicone molds.

In fact, Pouring liquid silicone rubber is a very simple method, but the most important point is to choose the right hardness according to the size of the product. The general size of the product between 50-100 cm, the choice of hardness in about 30 degrees of liquid silicone rubber; size of the product in more than 100 cm, choose 35-40 degrees of liquid silicone rubber; product size less than 30 cm, choose 15-20 degrees of liquid silicone rubber. The working time of liquid silicone rubber is usually 30-40 minutes, and it takes 3-4 hours to fully cure. However, the mould is prone to air bubbles and they are difficult to drain out. This is why it is necessary to use a vacuum machine to remove the air bubbles when pouring liquid silicone rubber.

The brushing process is very technical and involves determining the highest part of the moulding line according to the structure and pattern of the product, and then dividing the product into two parts. To make the parting molds, you need to use clay as an auxiliary material, which is reusable. The operation time for brushing a layer of silicone is 10-15 minutes. The number of layers of silicone molds is around 3-4 layers, with a few layers of gauze in between to enhance the tear resistance.

Silicone molds are taken after 24 hours of curing, it will improve the life of the silicone molds and duplication times .

Making silicone molds is a versatile and relatively straightforward process, suitable for a variety of applications, from art and crafts to industrial manufacturing. Here’s a step-by-step guide to creating a silicone mold:

Materials and Tools Needed

Silicone Rubber (RTV2) prepare : A two-component silicone rubber that includes a base (Part A) and a curing agent (Part B).
Mixing Silicone: Used for accurately measuring and mixing the silicone components.
Release Agent (optional): Applied to prevent the silicone from adhering to the original object or the mold box.
Mold Box or Containment: A container to hold the object and the silicone.
Object to Mold: The item you want to replicate.
Scale: For accurate measurement of silicone components.
Gloves and Protective Gear: To protect your hands and clothing.
Vacuum Chamber (optional): For degassing the silicone, removing trapped air bubbles.

Step-by-Step Process

Prepare the Object and Mold Box:

Clean the object you want to mold, removing any dust, dirt, or oils.
Position the object in the mold box, ensuring it’s securely held in place. The mold box should be slightly larger than the object to provide a sufficient silicone layer.
If necessary, apply a release agent to the object and mold box to prevent the silicone from sticking.

Measure and Mix the Silicone:

Measure the required amount of Part A and Part B silicone components according to the manufacturer’s instructions. Use a scale for accuracy.
Pour both components into a mixing cup and stir thoroughly. Be sure to scrape the sides and bottom of the cup to ensure a complete mix.
If you have a vacuum chamber, place the mixed silicone inside to degas it, removing any air bubbles.

Pour the Silicone:

Pour the silicone mixture slowly into the mold box, starting from one corner and allowing it to flow over the object. This helps minimize air bubbles.
Pour in a thin stream to further reduce the chance of trapped air.
Fill the mold box until the object is completely covered, ensuring there is an adequate thickness of silicone around and above the object.

Curing the Silicone:

Allow the silicone to cure according to the manufacturer’s instructions. Curing time can vary depending on the silicone type and environmental conditions (temperature, humidity).
Avoid disturbing the mold during the curing process to prevent deformation.

Demolding:

Once the silicone has fully cured, carefully remove the mold box or containment.
Gently peel away the silicone mold from the object, starting from one edge and working your way around. Be careful not to tear the mold.

Finishing:

Inspect the mold for any imperfections, such as trapped air bubbles or thin spots. Minor imperfections can often be repaired with additional silicone.
If necessary, trim any excess silicone from the edges of the mold.

Tips and Best Practices

Ventilation: Work in a well-ventilated area, especially if using release agents or solvents.
Room Temperature: Silicone cures best at room temperature (around 23°C or 73°F). Extreme temperatures can affect curing time and final properties.
Use of Release Agents: While not always necessary, release agents can make demolding easier, especially with complex shapes or porous materials.
Multiple-Part Molds: For complex objects, you may need to create a multi-part mold. This involves creating one part of the mold, allowing it to cure, and then pouring silicone for the second part.

By following these steps and paying attention to detail, you can create high-quality silicone molds suitable for a wide range of applications.