How to Use One To One Rapid Mold Rubber for Casting

By Quality Tools & Supplies for Hobbys, DIY & Crafts - Micro-Mark Tools | Published: 2026-10-30

Category: How-to Guides

Learn the step-by-step process of using One To One Rapid Mold Rubber to create silicone molds for casting metal parts. Perfect for hobbyists and DIYers.

Quick Answer

One To One Rapid Mold Rubber lets you create detailed silicone molds for casting metal parts without heat, using a simple 1:1 mix and a 4-hour cure time.

Why Use RTV Silicone for Metal Casting?

Room Temperature Vulcanizing (RTV) silicone like One To One Rapid Mold Rubber is ideal for hobbyists because it doesn't require heat or vacuum equipment. It captures fine detail from your original part and releases cleanly from cast metal.

The 4-hour cure time is a trade-off: you get a usable mold in a single afternoon, but you must work carefully during the pot life to avoid bubbles or incomplete coverage.

Step-by-Step Mold Making Process

Prepare Your Work Area and Original Part: Clean the part you want to duplicate and place it in a disposable container. Make sure it is free of dust and oil so the silicone captures every detail. Use a release agent if the part is porous. Common mistake: skipping the release agent on porous materials can cause the mold to stick.
Mix the Rubber Thoroughly: Stir Part A and Part B in a 1:1 ratio by volume or weight. Scrape the sides and bottom of the mixing cup to ensure a uniform color. Mix for at least 2 minutes. Checkpoint: an uneven color indicates incomplete mixing, which leads to soft spots in the mold.
Pour the Mixture Over the Part: Pour the mixed silicone slowly into the lowest point of the container to let air escape. Cover the part completely with at least 1/4 inch of rubber above the highest point. Common mistake: pouring too fast traps air bubbles against the part surface.
Let It Cure for 4 Hours: Allow the mold to sit undisturbed at room temperature (65-75°F) for 4 hours. Do not move or disturb it during this time. After curing, peel the mold away from the part. Checkpoint: if the mold feels tacky after 4 hours, let it cure longer – cooler temperatures slow the reaction.
Cast Your Metal Part: Place the cured silicone mold in a support box (if using a 1-part mold) or assemble the two halves (if using a 2-part mold). Pour molten metal into the cavity and allow it to cool before removing the casting. Common mistake: not supporting a thin silicone mold can cause distortion during metal pouring.

Product Highlight

One To One Rapid Mold Rubber: One To One Rapid Mold Rubber is a general purpose RTV silicone that de-airs without a vacuum and cures in 4 hours. This means you can create detailed molds at room temperature, making it accessible for small workshops without specialized equipment.
One To One Rapid Mold Rubber