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Yes, a pourable caulk-based mold mixture has been reported—but only as one reader’s 2010 experiment, not as a standardized or validated recipe. The report combined 100% silicone caulk, paint thinner and cornstarch, with approximate ratios and times that may change substantially between caulk and solvent formulations. Treat the figures below as an anecdotal starting point, not guaranteed specifications. For predictable detail, cure and compatibility, use a purpose-made pourable silicone mold-making product selected for your project.
What the reported caulk method contains
Make: published an anonymous reader’s experiment on November 4, 2010. The reader described mixing silicone caulk with paint thinner, then adding cornstarch. The article does not identify a universal caulk formulation, a single solvent specification or laboratory-tested performance data.
| Reported use | Caulk and thinner proportion | Cornstarch | Reported result |
|---|---|---|---|
| Basic mold mixture | Approximately 4:1 caulk to paint thinner | About 1 tablespoon | About 5–10 minutes of working time and about 45 minutes to set, according to the reader |
| Thinner casting mixture | Silicone-to-thinner ratios ranging from 3:4 to 1:2 | About ½ tablespoon | The reader said the cornstarch thickened the mixture |
| Suggested more-pourable variation | Based on the thinner mixture | About ¼ tablespoon suggested | The reader expected greater pourability and a longer set time |
Those quantities and timings describe that individual experiment. They are not product specifications, and they should not be presented as a universal formula for every tube of caulk or every paint thinner.
Why the same ratio may behave differently
Caulk formulations are not interchangeable
“100% silicone” identifies a broad product category, not an identical formulation. Additives, cure systems, viscosity and other ingredients can differ by product. A ratio that appeared workable with one caulk may cure differently, remain weak or fail with another.
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- PREMIUM MOLDS MAKING SILICONE MATERIAL: Our translucent liquid silicone for mold making are platinum-cured silicone, made by safe silicone material, non-toxic and no odor, very flexible, soft and clear. You could also mix mold making silicone rubber with mica powder to create new colors.
- EASY MIXING & POURING: This silicone molds making kit includes part A and part B, the mix ratio is 1:1 by weight. Pour the Part A and Part B together, then stir the silicone rubber for 5 minutes, make sure to stir the liquid siicone rubber mixture thoroughly for better results. The working time is 30 minutes at room temperature.
- NO BUBBLES: The bubbles of liquid silicone will automatically disappear within 2 hours, no vacuum degassing is necessary. The working time of making mold kit is 40 minutes at room temperature and the complete cure time is at least 4 hours at room temperature, it varies on your mold size and thickness. If it's little sticky, please extend the curing time of silicone rubber
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Solvent can change strength, cure and shrinkage
A secondary caulk-mold reference warns that the solvent chosen and the amount used can affect material strength, cure time and shrinkage. These are concerns to investigate for the exact products involved, not performance values established for the reported mixture.
Working time is not a guaranteed cure schedule
The reported 5–10-minute working window and 45-minute set are approximate observations from one experiment. Temperature, humidity, layer thickness, mixing quality and the particular caulk and solvent can all alter the result. A surface that feels set may not have the final properties needed for demolding or casting.
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- EASY MIXING & POURING: This silicone molds making kit includes part A and part B, the mix ratio is 1:1 by weight. Pour the Part A and Part B together, then stir the silicone rubber for 5 minutes, make sure to stir the silicone rubber mixture thoroughly for better results. The working time is 5 minutes at room temperature
- NO BUBBLES: The bubbles of liquid silicone will automatically disappear within 2 hours, no vacuum degassing is necessary. The working time of making mold kit is 5 minutes at room temperature and the complete cure time is at least 6-12 hours at room temperature, it varies on your mold size and thickness. If it's s little sticky, please extend the curing time of silicone rubber
- GREAT FOR BEGINNER: If you're new to the mold making, this mold making kit is a perfect choice for you to try! No special skills or tools are needed. You could enjoy this fun and creative activity all day. HOW to CLEAN: If there's any spill, please clean with soapy water or rubbing alcohol
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Safety and compatibility checks before experimenting
- Read the label and safety data sheet for the exact caulk and solvent. The 2010 report is not a safety assessment.
- Account for solvent exposure and follow the products’ handling, ventilation, storage and disposal directions rather than assuming that a craft recipe makes the combination safe.
- Do not assume the mixture is food-safe, skin-safe or suitable for a particular resin. The cited sources establish none of those uses.
- Check the casting material’s own instructions for compatibility with the cured mold and any required release system.
- Make a small trial piece before committing a detailed master or a large quantity of casting material.
When purpose-made pourable silicone is the better choice
Purpose-made pourable silicone mold-making kits are documented products with technical information intended for mold work. They are not equivalent to the caulk experiment by default, but their documentation gives you a more reliable basis for selecting hardness, cure behavior and compatibility.
Match the mold to the geometry
Formlabs identifies target geometry, holes and undercuts as key mold-selection considerations. Fine detail and deep undercuts may require a flexible mold design, a split mold or another approach that allows safe removal without tearing the mold or damaging the master.
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- EASY 1:1 TWO-PART SILICONE MIX — Mix equal parts A and B by weight or volume and stir thoroughly for 3–5 minutes. About 30 minutes of working time at 77°F/25°C gives more time to pour, position originals and fill detailed shapes.
- LOW-VISCOSITY LIQUID SILICONE FOR MOLDS — Smooth-flowing platinum-cure silicone reaches narrow details and intricate textures while helping trapped air rise naturally. Slow mixing and thin-stream pouring can help create cleaner molds.
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- 4-HOUR INITIAL ROOM-TEMPERATURE CURE — At about 77°F/25°C, initial cure is around 4 hours and full cure typically takes 4–6 hours. Larger molds, thicker pours or cooler rooms may require more time before demolding.
Match the method to production scale
A one-off mold has different cost and repeatability requirements from a mold intended for repeated production. A documented pourable system is generally easier to evaluate for recurring work because its technical data can be consulted from batch to batch.
Match the mold to the casting material
Resin, plaster, wax and other casting materials can interact differently with a mold surface or release agent. Follow the mold-maker’s and casting-material manufacturer’s instructions for the exact combination instead of inferring suitability from the word “silicone.”
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- 【Wide Application】: LET'S RESIN high-performance mold making silicone rubber is idea for making highly-detailed molds as well as 3D silicone molds; very ideal for art craft use, casting material like resin, wax, gypsum, soap, candle, polymer clay, easily make your own silicone molds. Translucent clear color allow you to mix with mica powder, chameleon powder, and even glow-in-the-dark pigment to create a unique color shade and offer you more DIY fun.
Use technical documentation for reproducibility
Smooth-On’s catalog includes a Pourable Silicone Starter Kit, product documents and technical information for silicone thinner. That establishes a purpose-made product category; it does not validate the caulk recipe or prove that any one kit suits every project. Compare the stated cure, hardness, mixing requirements and compatibility information with your design before buying.
Release agent requirements for silicone-on-silicone work
Smooth-On’s guidance states: “Silicone-to-silicone applications such as making two-part molds or casting silicone into silicone are possible, but require a release agent.” If you are pouring silicone against cured silicone, consult the applicable technical bulletin and safety data sheet, choose a release product approved for that material combination and test it on a small area first. Do not generalize this requirement to every mold-and-casting combination without checking the manufacturers’ instructions.
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- 【64oz Mold Making Kit】: This silicone mold making kit comes with 2 bottles of liquid silicone, each bottle containing 32oz of platinum cure silicone, as well as 5pcs wooden mixing sticks,6pcs disposable protective gloves; a perfect slicone mold kit for beginners to try, satisfying your various needs.
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- 【No Bubbles】: No vacuum degassing is necessary! The bubbles of silicone for mold making will automatically disappear within 1.5 hours at room temperature due to its low viscosity(viscosity 1500) feature.
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A practical decision guide
| If your project involves… | Prioritize… |
|---|---|
| A one-off, low-consequence experiment | A small test using the exact caulk and solvent, with label and safety-data-sheet review |
| Fine detail, holes or undercuts | A mold design and material documented for flexible demolding and the geometry of the master |
| Repeated production | Predictable, documented cure and mechanical properties from a purpose-made pourable silicone |
| Silicone cast into silicone | A compatible release agent and a manufacturer-recommended test |
| A food, skin or other regulated application | Explicit certification and instructions for the exact product system; do not rely on the caulk experiment |
Bottom line on the pourable caulk recipe
The 4:1 caulk-to-paint-thinner mixture, the 3:4 to 1:2 thinner variations and the cornstarch amounts are useful historical observations, but they are not a standardized recipe. Formulation differences, solvent effects, uncertain shrinkage and unverified final properties make the result difficult to predict. Use the report only as an anecdotal experiment, and choose documented pourable mold-making silicone when geometry, repeatability or casting compatibility matters.
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