How to use liquid silicone to make mold?

Unleash your creativity and start by replicating the first part
Do you have a perfect 3D print, a finely crafted figurine, or a unique industrial prototype that you want to replicate safely and accurately?

Looking at your beloved work, the uniqueness is precious, but do you also want to share it with friends, make it into a small batch of products, or just keep a backup just in case? Maybe more variations and ideas based on this design have emerged in your mind, but you are struggling to turn it into reality efficiently? Manual measurement, remodeling, and even remaking are not only time-consuming and laborious, but also difficult to guarantee the perfect reproduction of every exquisite detail and complex curve of the original.

The good news is that the magic key to breaking the shackles of “uniqueness” and opening mass replication is in your hands-that is, learning how to make silicone molds. This seemingly simple first step is the key turning point to turn your “uniqueness” into “within reach”. It is not only the starting point of replication technology, but also the cornerstone of your unlimited creativity. Imagine that with just a carefully crafted silicone mold, you can easily cast a replica that is almost identical to the original, in any material and quantity you want.

And the starting point of all this is the process of making a mold with liquid silicone, which starts from your fingertips. It does not require expensive industrial equipment. With basic skills, you can achieve accurate replication in the studio or even at home. Say goodbye to the “cautiousness” of a unique work and embrace the mass release of creativity – learning how to use liquid silicone to make molds is the first and most critical step you take. Copying is no longer a luxury, but a natural extension of your creative landscape. Let’s get started, starting with replicating your first perfect part and opening up endless possibilities.

Silicone mold production technology comparison analysis table

This guide will not only teach you step by step how to make silicone molds for resin processes, but also reveal how the industry uses liquid silicone molding technology to efficiently produce tens of thousands of precision parts, and explain how this affects the final injection molding price.

Here’s What You’ll Learn

• A seven-step practical process to master the perfect silicone mold, helping you avoid 90% of common failure traps.
• Professional secrets to overcome the bubble problem: Why is vacuum degassing the watershed between amateurs and professionals?
• Experts answer three core questions: What to do if silicone sticks to silicone? How to make large/human molds? Is the caulking agent “hack” reliable?
• Key decision point: When should you switch from manual molding to industrial-grade liquid silicone injection molding (LSR)?
• In-depth FAQ from material experts: How to choose “Shore hardness”? Why is the mixing ratio so strict? Where to buy a kit?

Now, let’s explore the essence of liquid silicone mold making and accurately replicate your creativity.

Why should you trust this guide? From the perspective of LS liquid silicone molding experts

At LS, we are not just talking on paper. Our daily work is to operate precision injection molding machines with tens of tons of clamping force to mass-produce key components related to safety and performance: medical-grade seals, automotive connectors, and consumer electronics buttons. The success of these high-demand products stems from our deep understanding of the essence of liquid silicone (LSR) and industrial-level practice.

Why can this industrial experience guide your DIY project?

Because the core principles of silicone are not limited to scale. Whether it is the tons of raw materials we handle or the one kilogram of handmade materials in your hands, the physical properties, flow laws and curing behavior of silicone are consistent.

We are proficient in the “temperament” of silicone: How does different hardness affect the difficulty of demolding and shrinkage? How to avoid tearing? – This knowledge directly determines the success or failure of your hand-made workpiece.

We are well versed in the “bubble killer”: medical-grade bubble-free sealing is ensured through processes such as vacuum degassing. This understanding of the causes of bubbles (air, moisture, poor exhaust) can help you minimize bubble troubles at home.

We know the way to “perfect replication”: How to design molds (parting lines, gates, vents) to accurately replicate details and avoid flash or material shortages? This is the core issue in our mass production.

This guide is to refine these rigorous industrial-proven LSR expertise into practical tips that you can use immediately. We understand the essence of silicone and put this deep experience and expertise into it, aiming to provide you with reliable guidance to help you overcome DIY challenges and confidently master liquid silicone. Industrial-level knowledge is the cornerstone of your trustworthiness.

How to make a perfect silicone mold by hand: 7 steps

The key to making a high-quality silicone mold is to pay close attention to detail. Whether it is used to replicate delicate artwork, industrial prototypes or other complex shapes, following the seven proven core steps below will effectively avoid 90% of the common mistakes made by novices, significantly increase the success rate, and ultimately obtain a smooth, accurate and durable perfect mold.

Step 1: Finely crafted prototype (Master) and impeccable mold box (Mold Box)

(1) Prototype preparation (Master Preparation): This is the foundation of the success or failure of the mold! The surface quality of your prototype will be directly reflected in the final mold and replica.

• 3D prints: Layer lines must be completely removed! Use sandpaper (gradually transition from coarse to fine mesh, such as 400 mesh -> 800 mesh -> 1000 mesh+) to carefully polish. Looking for the ultimate smoothness? Subsequent polishing (such as using polishing paste, sandblasting or solvent fumigation) can bring a mirror-like effect. Be sure to remove all support residues and dust.
• Other materials (such as clay, wood, resin): The surface should also be flat, smooth and free of defects. Check and repair any cracks, pits or unevenness. Key point: Perfect prototype surface = perfect mold cavity.

(2) Mold Box Construction: The mold box is responsible for containing the liquid silicone and shaping the mold. The core requirements are sturdiness, no leakage and reasonable size.

• Material selection: Lego bricks (flexible and easy to use, can be disassembled and assembled repeatedly), acrylic sheets (use tape or hot melt glue to seal the seams), special mold box kits (best choice, good sealing) or sturdy cardboard (the inner wall must be smooth and leak-proof).
• Size key points: Leave at least 1-1.5 cm of space between the inner wall of the mold box and any part of the prototype to ensure that the silicone is thick enough to ensure the strength and durability of the mold. The mold box height should exceed the highest point of the prototype by at least 1 cm.
• Sealing is the key: After assembly, be sure to check all seams and bottom! Use hot melt glue (fast and effective) or putty (good plasticity) to carefully seal the inner edge of the bottom of the mold frame and the seam where the prototype meets the base plate to prevent silicone leakage. Tips: Plan the parting line position in advance (if a two-piece mold is required), and mark it on the prototype.

Step 2: Watertight Sealing and the Right Release Agent (Sealing & Release Agent)

(1) Sealing (Sealing – again): The mold frame sealing in the previous step is the key line of defense to prevent silicone leakage. Make sure it is foolproof. Checkpoints: All seams, the junction between the bottom of the mold frame and the base plate, and the junction between the prototype and the base plate.

(2) Release Agent (Release Agent): This is the secret weapon to ensure that you can successfully peel the cured silicone mold from the prototype without damage!

• Why is it necessary? Even if silicone itself has a certain degree of release properties, for prototypes with complex surfaces, undercuts or materials that are prone to adhesion (such as certain resins and wood), spraying a thin layer of special release agent can significantly reduce the difficulty of separation and protect the prototype and mold surface.
• How to do it?

Choose a special release agent suitable for platinum silicone (such as water-based or solvent-based).

Spray or apply a thin and even layer on the prototype surface. Do not spray too thick! Otherwise, it may cause texture on the mold surface or affect the reproduction of details.

Wait for the release agent to dry completely (follow the product instructions, usually a few minutes). Note: The release agent usually does not need to be applied to the inner wall of the mold frame (unless the mold frame material is particularly easy to stick), and the silicone is mainly separated from the prototype.

Step 3: Precise Measure & Mix

(1) Know your material: We recommend using platinum catalyzed addition-cured silicone. It has low odor, extremely low shrinkage, good flexibility after curing, high tear strength, and can reproduce ultra-fine details. It consists of component A (base glue) and component B (catalyst).

(2) Golden rule: Mixing ratio is lifeline!

The most common ratio of platinum silicone is 1:1 (volume ratio or weight ratio) or 10:1 (weight ratio). You must strictly adhere to the exact ratio marked on the product packaging! The wrong ratio will cause the silicone to not cure completely (too soft, sticky) or cure too quickly/too slowly, or even not cure at all, and the entire mold will be scrapped.

Tools: Use an accurate electronic scale (recommended, especially for 10:1 ratio) or an accurate measuring cup (make sure the scale is clear, only for 1:1 volume ratio). Avoid using rough container estimates.

(3) Mixing:

Weigh/measure the required amount of component A and component B into a clean, dry mixing container.

Use a stirring rod or a stirring knife to mix thoroughly and evenly. Key: Be sure to scrape the bottom and side walls of the container to ensure that all corners of the material are fully mixed together. Uneven mixing is the culprit for local non-curing.

The mixing time usually takes 2-5 minutes until the color is completely uniform (no streaks). Note: From the beginning of mixing, the “operating time” of the silicone is on the countdown!

Step 4: Vacuum degassing/degassing – the only way to achieve professional quality

(1) Why is this a watershed? During the mixing process, a large number of tiny bubbles will inevitably be drawn into the silicone. If not removed, these bubbles will remain in the mold after curing, and eventually form annoying defects (small bumps or pinholes) on the surface of the replica. Vacuum degassing is the most effective way to remove these bubbles and obtain an optically clear, flawless mold surface.

(2) Operation steps:

Pour the mixed silicone into a clean, open container (such as a plastic cup) that is at least 2-3 times larger than the volume of the silicone.

Place the container in the vacuum chamber.

Cover the lid and start the vacuum pump. As the pressure decreases, the volume of the silicone will expand dramatically (bubbling, rising), and the internal bubbles will be sucked out.

Maintain the vacuum state until there are basically no large bubbles on the surface of the silicone (usually it takes tens of seconds to a few minutes, depending on the amount and viscosity of the silicone). Note: Monitor closely to prevent the silicone from overflowing the container!

Release the vacuum slowly (to avoid bubbles being pushed in again). Usually, it is necessary to repeat the vacuuming 1-2 times to achieve the best effect.

(3) What if there is no vacuum pump? Although the effect is compromised, you can try:

Slowly and gently stir the mixed silicone, and let it stand for a few minutes to let the large bubbles naturally float to the surface and burst.

“Pouring method” degassing: Slowly pour the silicone from one container to another, and stretching the liquid flow will help to remove some bubbles.

Use low-viscosity, self-draining silicone. But be sure to note: Without vacuum degassing, it is almost impossible to completely eliminate tiny bubbles, which is a major compromise for molds that require high precision.

Step 5: The Art of Pouring

(1) Core Strategy: Let the silicone gently wrap around the prototype, rather than violently impact it. The goal is to minimize the generation of new bubbles and allow the silicone to naturally penetrate every tiny corner and expel potential air pockets.

(2) Correct Technique:

Lift the container of degassed silicone to a higher position above the mold frame (for example, 30 cm or higher).

Pour the silicone into a thin, continuous, and stable “line”.

Let this “line” first fall on a corner or open space at the bottom of the mold frame (do not pour directly on the prototype!).

Move the pouring point slowly and evenly, allowing the silicone liquid flow to spread naturally from low to high, gradually covering the bottom of the mold frame, and then gently wrapping the entire prototype from bottom to top.

Why it works? This “thin line high pouring” method can effectively stretch the silicone liquid flow, helping the remaining tiny bubbles to merge and burst during the rising process; the slow flow reduces turbulence and the entrapment of new bubbles; allowing the silicone to fill from the lowest point helps the air to be pushed upward and discharged.

Step 6: Patient Curing

(1) Understand the concept of time:

Pot Life: refers to the time from when the silicone is mixed to when it becomes too viscous to be poured or degassed. It is crucial to complete the first five steps within the pot life!

Cure Time: refers to the time from when the silicone is mixed to when it is completely cured and reaches usable strength. This is the waiting time you must give.

(2) Environmental influence: Temperature is the master of curing speed! The ideal curing temperature for most platinum silicones is 20°C – 25°C.

Too low temperature (<18°C): The curing speed is significantly slowed down, which may take several days or even longer, and the curing may not be complete.

Too high temperature (>30°C): The pot life is drastically shortened, and there may not be enough time to complete pouring and degassing. It may also cause stress or affect performance due to too fast curing.

(3) Key points:

Place the cast mold in a clean, dust-free, stable place with suitable temperature.

Strictly follow the curing time specified in the product manual (usually 24-48 hours at room temperature). Do not rush to demould just because the surface looks dry! The inside may not be fully cured yet.

If the ambient temperature is low, you can consider using a constant temperature box or a heater within a safe range (to avoid local overheating) to accelerate curing, but be cautious.

Step 7: Careful Demolding

(1) Checking the cure: After the estimated cure time is over, gently touch an unimportant area of ​​the mold edge (or a reserved test point) to confirm that the silicone has fully cured (flexible and non-sticky).

(2) Removing the mold frame:

Carefully remove the mold frame (Lego, acrylic sheet, or special mold frame parts). If an adhesive seal is used, you may need to carefully pry or cut the seal. Be gentle and avoid twisting the mold.

(3) Separating the mold from the prototype:

This is the most tense moment! The goal is to separate the mold and the prototype without damage.

Start from the edge of the mold: Use your fingers or a blunt tool (such as a plastic scraper or butter knife) to very gently peel the silicone from the prototype starting from the very edge of the mold. Never pull hard or pry hard from one point!

Take advantage of flexibility: Silicone is elastic. For structures with undercuts, you can slowly and gently stretch and flip the edge of the mold to allow the silicone to gradually slide off the undercut. Patience is key!

If you have sprayed the mold release agent and done it correctly, the separation will usually be relatively smooth. If you encounter resistance, go back to the edge and try to peel gently in the other direction.

After successfully removing the prototype, check whether the mold cavity is intact, smooth and undamaged. Congratulations, a perfect silicone mold is born!

Expert Tips & FAQs

1.Will liquid silicone stick to silicone molds?

Authoritative answer: “Yes, liquid silicone will adhere firmly to silicone molds. This is due to the extremely strong affinity between silicone molecules, which can achieve perfect self-adhesion. If you need to use a silicone prototype (for example when making a two-piece mold) to remake a new silicone mold, the prototype surface must be pre-treated with a special “silicone to silicone” release agent. It is important to note that ordinary release agents (such as wax or PVA) are generally ineffective in such cases and cannot reliably prevent adhesion.”

2. How to make molds of large objects or human body parts?

(1) Large object molds:

Core challenges: The main difficulties in making large molds are the high cost caused by the huge amount of silicone used, the violent exothermic reaction that may occur during curing (which may cause deformation or even burn risks), and ensuring that the final mold has sufficient structural strength and dimensional stability to support its own weight and injection molding pressure.

Expert advice: The “Brush-On Method” is recommended. The specific steps are: first, manually brush or pour a layer of relatively high viscosity (thick) silicone on the surface of the model to ensure that all details are covered. After this layer of silicone cures, a rigid support material (such as plaster bandage, fiberglass reinforced plastic (FRP) or polyurethane resin) must be used on the outside to make a solid back mold (also called a mother mold or shell). This back mold is crucial. It can provide strong structural support to prevent large silicone molds from deforming, collapsing or tearing due to their own weight or injection molding pressure during subsequent use.

(2) Human body part molds (such as hands, faces):

First principle: Safety first! It is absolutely forbidden to use industrial-grade or non-designated silicone in direct contact with the skin.

Professional requirements: You must use strictly certified “skin-safe” or “human-specific” silicone materials. This type of silicone has a special formula, high biocompatibility, mild curing heat, and does not contain additives that are harmful to the human body. During operation, you must strictly follow the product instructions and safety regulations to ensure the comfort and safety of the person being molded.

3. (Clarifying common misunderstandings) Can I make my own mold silicone using building caulk and soapy water?

(1) Expert analysis: “The method of using acidic building caulk (such as bathroom anti-mold silicone) mixed with soapy water to simulate mold silicone is a ‘cheat’ method that uses the caulk to solidify when it encounters water vapor in the air. We strongly do not recommend this method for any project that requires precision, durability or is of great value.”

(2) Key defects:

High shrinkage: The shrinkage rate of homemade ‘silicone’ is very large, resulting in severe deformation and dimensional inaccuracy of the final casting.

Poor detail restoration: Its ability to capture fine surface textures and complex details is extremely poor and cannot meet professional reproduction requirements.

Contains harmful substances: Acidic caulks usually contain irritating solvents, anti-mold agents and other chemicals, which may release irritating gases during the curing process, and the cured material is not suitable for contact with food or skin.

Unstable performance: Factors such as mixing ratio, ambient temperature and humidity have a great impact on the curing effect, resulting in extremely unstable and unpredictable performance.

(3) Applicability: This method can only be used for extremely rough, one-time temporary applications, such as making a simple shape for temporary support or very basic experiments. For any mold making that requires quality, precision and safety, be sure to use professional mold making silicone.

When should you switch from hand molding to professional liquid silicone injection molding (LSR)?

When your project goes from a ‘hobby’ to a ‘product’, from ‘one’ to ‘ten thousand’, the limitations of manual molding will become apparent. At this time, you need to understand the industrial-grade solution – liquid silicone injection molding (LSR).

Comparison table: Handmade mold (DIY) vs. LSR industrial injection molding

FAQ – Answers to all your questions about silicone molds

1. How to use liquid silicone?

There are three main steps to using liquid silicone: First, you must mix components A and B in strict accordance with the ratio specified in the product instructions and stir them thoroughly; second, it is strongly recommended to vacuum degas the mixed silicone to remove bubbles; finally, slowly pour the silicone into the prepared mold frame and wait for it to completely solidify.

2. Where can I buy a silicone mold making kit?

For beginners, we recommend buying a silicone mold making kit from a well-known art supply store or model supply store, which usually contains all the materials needed to get started. For industrial applications, material selection is much more complicated, and you need to contact a professional injection molding service provider like us to obtain a customized solution based on specific product requirements (such as temperature resistance, tear strength, production batch, etc.).

3. What is the best silicone rubber for mold making?

There is no so-called “best” silicone rubber, only the “most suitable” choice. The key is to choose the right Shore Hardness: low-hardness silicone (such as Shore 10A) is very soft and can easily demold complex shapes and fine details; while high-hardness silicone (such as Shore 40A) is firmer and less prone to deformation, and is more suitable for making molds with simple structures that require strong support. The choice depends on your specific model and needs.

Conclusion

Handmade silicone molds are a great starting point for your creative ideas, allowing you to replicate your favorite things with your own hands. However, when your goal turns to commercial production, large-scale manufacturing and the pursuit of extreme precision, liquid silicone injection molding is a more professional and reliable choice.

If your project has gone beyond the DIY stage and needs to produce hundreds of high-quality, high-precision silicone parts, LS’s professional team is ready! Contact us now to get:

1. Professional consultation on customized injection molding manufacturing services
2. A transparent and competitive injection molding solution quotation
3. Let us help you efficiently transform your creativity into market competitiveness!

 📞 Phone: +86 185 6675 9667 📧 Email: info@longshengmfg.com 🌐 Website: https://www.longshengmfg.com/