Molding & Casting.
Silicone produces flexible molds that capture the finest details and deliver many dimensionally accurate castings, from architectural models to art and jewelry, up to food-grade series production. This overview guides you from the crosslinking system and Shore hardness to the release agent, tailored to your casting material. SILITECH supplies the in-house brand SILISIL from the Gümligen warehouse and provides advice on selection and data sheets.
On this page
Why Silicone · Systems · In Comparison · Selection Guide · By Application · Selection Criteria · Processing · Common Errors · FAQ · Further Reading
Why Silicone
Why silicone leads in mold making
Silicone is the dominant material in mold making because it combines flexibility, detail accuracy, temperature resistance, and durability in one material. A silicone mold reproduces the finest surface details, can be demolded elastically, and, depending on the type, delivers hundreds to thousands of dimensionally accurate castings.
- Detail fidelity: Reproduces the finest contours, negative radii, and textures.
- Elastic demolding: even deep undercuts come out cleanly.
- Often self-releasing: in many cases without a release agent.
- Durable: many casts per mold, good unit costs in series production.
- Wide temperature range: suitable also for wax and reactive resin systems.
Compared to rigid molds made of plaster, polyurethane, or 3D printing, silicone demonstrates its strength wherever detail fidelity, undercuts, and repeat accuracy are critical.
The key parameters
What you decide on
Six key parameters determine the result. The crosslinking system and hardness set the framework, while the casting material and release agent determine the process.
Addition-curing (Platinum)
Precision, dimensional accuracy
Platinum-catalyzed, minimal shrinkage and highest detail and dimensional accuracy. Pot life adjustable, food-grade types available. Sensitive to inhibition by contaminants.
Condensation-curing (tin)
robust, economical
Tin-catalyzed, insensitive in handling and more cost-effective. Ideal for large molds and single castings. Slightly higher shrinkage and lower long-term stability than platinum systems.
Select Shore hardness
Flexibility by geometry
Soft types for deep undercuts and filigree negatives, harder types for flat, abrasive, or series applications. Hardness determines demoldability and service life.
Match casting material
Resin, concrete, plaster, wax
The casting material determines the system, hardness, and release agent. Acrystal, casting resins, concrete, plaster, wax, and low-melting-point metals place different demands on the mold.
Release agent
when necessary, which type
Silicone is often self-releasing. For silicone-on-silicone, reactive resins, or foreign molds, wax, PVA, silicone spray, or semi-permanent systems are required. Apply thinly, otherwise details suffer.
Avoiding inhibition
Sulfur, tin, amines
Addition-curing silicones do not cure in contact with sulfur, tin, amines, or latex. Sticky areas are the result. When in doubt, test compatibility or seal the surface.
System selection
Addition and Condensation Compared
The most important decision is the crosslinking system. Both profiles serve as orientation; specific values are provided in the data sheet and in the linked technical articles.
| Property | Addition-curing (Platinum) | Condensation-curing (tin) |
|---|---|---|
| Shrinkage | very low | moderate |
| Dimensional accuracy | very high | medium |
| Long-term stability | high | lower |
| Inhibition risk | present (sulfur, tin, amines) | low |
| Food contact | possible (compliant types) | generally no |
| Pot life | adjustable | Moisture-dependent |
| Price | higher | more economical |
| Typical application | Precision, series, food | large molds, single castings, budget |
Rule of thumb: Addition-curing for precision, food contact, and series production. Condensation-curing for large molds, one-off castings, and when budget is the deciding factor.
Shore Hardness as a Guide
| Hardness (reference value) | Character | Typical application |
|---|---|---|
| soft, approx. 10 to 20 Shore A | highly elastic | deep undercuts, filigree negatives |
| medium, approx. 25 to 35 Shore A | All-round | standard molds, casting resins, architecture |
| Hard, approx. 40 Shore A and above | abrasion-resistant, dimensionally stable | Series parts, abrasive casting materials, large flat molds |
Hardness ranges are guideline values. The specific type depends on geometry, cycle time, and casting material, and is specified in the data sheet.
Decision
Selection aid
| Requirement | Rather suitable | Note |
|---|---|---|
| Highest dimensional accuracy, fine details | Addition-cure silicone (platinum), rather soft Shore | Note inhibition |
| Large mold, budget, single casting | Condensation silicone (tin) | plan for slightly more shrinkage |
| Food, baking molds | Food-grade platinum silicone | Conformity according to data sheet |
| Mass production, many castings | Harder Shore, semi-permanent release agent | Ensure mold service life |
| Deep undercuts | Soft Shore | Demolding without tearing |
| Cast polyurethane or polyester resin | Release agents, e.g., silicone spray | protects the mold surface |
| Tight deadlines, iterations | fast-curing types | short pot life and demolding time |
| Concrete, plaster | medium to hard Shore | elastic, sharp-edged demolding |
The casting material, quantity, level of detail, dimensional tolerance, and food contact are decisive. The specific values are provided in the respective technical data sheet.
By Application
Typical Applications
Where silicone molds are in demand in practice, and what the material choice contributes.
Architecture & Model Making
Sub-mm detail
Filigree facades, terrain, and shadow gaps, reproducible small series from Acrystal or plaster. Precise and sharp-edged. Art & Model Making.
Art, Design & Jewelry
finest contours
Sculptures, reliefs, and jewelry molding with the highest detail reproduction. Precision types with minimal shrinkage reproduce the finest contours. Art & Model Making.
Series production of cast parts
many casts
Repeatable castings in quantity. Harder types and semi-permanent release agents ensure the mold's service life. Mechanical engineering.
Concrete & Plaster
Architecture, decoration
Molds and formwork for cast stone, stucco, and decor. The elastic demolding protects sharp edges and fine profiles. Construction.
Food & Baking Molds
compliant types
Food-grade platinum silicones for baking, chocolate, and ice molds. Conformity according to data sheet. Silicone products.
Prototyping & Iteration
short cycle time
Fast-curing types for tight deadlines and many iterations, with short pot life and early demolding. Mold-making guide.
Specification
What you should clarify before selection
- Casting material: Resin, concrete, plaster, wax, or metal, and how reactive it is.
- Quantity: Single piece, small series, or series production, which determines the required mold service life.
- Detail level and geometry: Undercuts, delicate webs, textures.
- Dimensional tolerance: how sensitive the part is to shrinkage.
- Food or skin contact: requires compliant types.
- Pot life, curing and cycle time: matched to throughput.
- Mold size and wall thickness: influence material, hardness, and stabilization.
- Release agent concept: depending on the casting material and quantity.
With this information, we jointly narrow down the system, hardness, and release agent, and review the data sheets.
Processing
Process cleanly
- Prepare the model: Clean, dry, and free of grease; seal porous surfaces such as plaster or wood.
- Check inhibition: For addition silicone, avoid contact with sulfur, tin, amines, and latex; if in doubt, test on a small area.
- Mix precisely: Adhere to the mixing ratio and mixing time, scrape down the sides of the container.
- Degas: in a vacuum or with a thin primer coat to prevent air inclusions.
- Pouring: Pour in a thin stream at the lowest point, slowly, so that air can rise.
- Demolding and post-curing: Allow the mold to post-cure and condition it with a test casting before series production.
Note: Use only as much release agent as necessary; a film that is too thick fills in fine details. When applying silicone onto silicone, a barrier layer is mandatory.
From practice
Common mistakes
- Inhibition: sticky, uncured areas due to contact with sulfur, tin, or amines.
- Air inclusions due to pouring too quickly or lack of degassing.
- Mold cracking due to too soft Shore hardness or too aggressive demolding.
- Distortion of large surfaces due to a system that is too soft without support.
- Release agent applied too thickly: fine details are lost.
- Reactive resin without release agent: the mold wears out prematurely.
FAQ
Frequently asked questions
Addition-curing or condensation-curing?
Addition curing (platinum) for precision, dimensional accuracy, food contact, and series production. Condensation curing (tin) for large molds, single castings, and tight budgets. The rule of thumb is shown in the comparison above.
Do I always need a release agent?
Not strictly necessary, silicone is often self-releasing. It becomes necessary for silicone-on-silicone applications, with reactive resins such as polyurethane, and with molds made of foreign materials. A preliminary test with the original materials is advisable.
Which Shore hardness is suitable?
Filigree objects and deep undercuts require soft types, while flat and abrasive applications require harder ones. The hardness ranges above are reference values; the specific type is specified in the data sheet.
How do I avoid inhibition?
For addition-curing silicones, avoid contact with sulfur, tin, amines, and latex; separate workstations and seal porous or critical surfaces. When in doubt, test on a small area.
How many casts does a mold withstand?
This depends on the material, hardness, casting material, and release agent, and ranges from a few to thousands of casts. Harder types and semi-permanent release agents increase the mold life.
Are the silicones food-safe?
There are food-grade platinum types for baking and food molds. Specific compliance depends on the product and is stated in the data sheet.
Further information
Matching Products, Worlds, Articles & Industries
Product groups: Silicone products · RTV-2 silicones (mold making) · Resins & potting compounds
Topic worlds: Silicones · Mold making & casting
Knowledge Articles: Silicone for Mold Making, the Complete Guide · RTV-2 Silicones in Architectural Model Making · Release Agents Compared
Industries: Art & Model Making · Construction · Mechanical Engineering · Medical Technology
Terms: refer to the Glossary (RTV-2, addition curing, condensation curing, Shore hardness, inhibition, release agents, pot life).
Technical Basis: The information is general guidance, not a product guarantee. The manufacturer's data sheets (TDS) and relevant standards are binding. Specific values (Shore hardness, shrinkage, pot life, temperature range, conformity) are product-dependent.
Contact
Unsure which mold-making system fits your casting?
Describe to us the casting material, quantity, level of detail, and geometry. We will recommend the system, hardness, and release agent, review the technical data sheets, and deliver from our Gümligen warehouse.