Introduction to Mold Making

A Guide to Choosing the Right Flexible Mold Material from TAP Plastics

When creating molds for casting, selecting the right mold material is crucial for achieving the best results. TAP Plastics offers five flexible mold materials, each with unique advantages and applications. This guide will help you understand the differences and choose the best option for your project.

Understanding RTV Mold Materials

RTV stands for Room Temperature Vulcanizing, meaning these materials cure into durable rubber at room temperature without requiring special ovens or heat supplies. All TAP Plastics mold materials are safe for indoor use. While liquid latex has a slight ammonia odor, the other materials are virtually odorless.

1. Premium Liquid Latex Rubber

Pros:

• Single-component; no mixing required

• Most economical option

• Easy application with a brush; no special tools needed

• Captures fine details

• Minimal need for mold release

Cons:

• Time-consuming (each coat takes up to 2 hours to dry; multiple coats required)

• Suitable only for molds that can be peeled off like a glove

Available Sizes: Pint, Quart, and Gallon

2. Urethane RTV

Pros:

• Extremely durable and strong

• Works well for casting concrete, plaster, polyester, and urethane

• Easy 1:1 mix ratio

• Low viscosity prevents bubble formation

• Can be used for multi-part molds

Cons:

• Requires a mold release to prevent sticking

• More expensive than latex due to material cost and usage volume

Available Sizes: Quart Kit, Two-Quart Kit, and Two-Gallon Kit

3. Silicone RTV

Pros:

• Virtually no need for mold release

• Works well for two-part molds and brush-on applications with thixotropic additives

• Captures extremely fine details (down to microscopic levels)

• Durable and flexible, ideal for deep undercuts

Cons:

• Higher cost than urethane

• Requires precise measuring of the 10:1 ratio (by weight) or 9:1 (by volume)

Available Sizes: 1 lb, 4 lb, and 8 lb tubs (plus hardeners)

4. Platinum Silicone

Pros:

• Superior tear resistance and chemical resistance for longer mold life

• Easy 1:1 mix ratio

• Super low viscosity eliminates the need for vacuum degassing

• Produces bubble-free, highly detailed molds

• Extremely flexible (hardness of 8 vs. 28 in standard silicone)

• Works well for clear resin casting without surface imperfections

Cons:

• Most expensive option

Available Sizes: Various sizes

5. Easy Mold Silicone Putty (Discontinued)

Pros:

• Fast cure time (3–5 minutes)

• Simple 1:1 mix ratio

• Ideal for small, quick molds

• Food-safe

Cons:

• Best for small-scale projects

Choosing the Right Mold Material

• For simple, budget-friendly projects with long drying times: Liquid Latex

• For strong, durable molds with easy mixing but requiring mold release: Urethane RTV

• For flexible, detail-rich molds without mold release: Silicone RTV

• For premium-quality, ultra-flexible, and long-lasting molds: Platinum Silicone

Final Thoughts

Selecting the right mold material depends on your project’s requirements, budget, and preference for ease of use. Experimentation and practice will help refine your mold-making skills, ensuring professional results in no time!