Molds & Molding.
Silicone creates flexible molds that reproduce the finest details and produce numerous dimensionally accurate castings, from architectural models to art and jewelry, all the way to food-grade serial production molds. This overview covers everything from the curing system and Shore hardness to the release agent, tailored to your casting material. SILITECH supplies its own brand, SILISIL, from its warehouse in Gümligen and offers advice on selection and data sheets.
On this page
Why silicone? · Systems · Comparison · Selection guide · By application · Selection criteria · Processing · Common mistakes · FAQ · Further information
Why silicone
Why silicone is leading in mold making
Silicone is the dominant material in mold making because it combines flexibility, precision, temperature resistance, and durability in a single material. A silicone mold reproduces the finest surfaces, can be demolded elastically, and, depending on the type, produces hundreds to thousands of dimensionally accurate castings.
- Attention to detail: reproduces the finest contours, negative radii and textures.
- Elastic demolding: even deep undercuts come out cleanly.
- Often self-releasing: in many cases without release agents.
- Durable: many castings per mold, good unit costs in series production.
- Wide temperature range: also suitable for wax and reactive resin systems.
Compared to rigid forms made of plaster, polyurethane or 3D printing, silicone demonstrates its strength wherever attention to detail, undercuts and repeatability are important.
The adjusting screws
What you decide
Six adjustable parameters determine the result. The crosslinking system and hardness set the framework, the casting material and release agent the process.
Addition crosslinking (platinum)
Precision, dimensionally accurate
Platinum-catalyzed, minimal shrinkage and highest detail and dimensional accuracy. Adjustable pot life, food-grade grades available. Sensitive to inhibition by contamination.
Condensation crosslinking (tin)
robust, economical
Tin-catalyzed, insensitive to handling, and more affordable. Ideal for large molds and individual castings. Slightly higher shrinkage and lower long-term stability than platinum systems.
Select Shore hardness
Flexibility according to geometry
Softer grades are used for deep undercuts and delicate negatives, harder grades for flat, abrasive, or serial applications. Hardness determines demoldability and tool life.
Select 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 needed which type
Silicone is often self-releasing. When bonding silicone to silicone, reactive resins, or foreign materials, wax, PVA, silicone spray, or semi-permanent systems are necessary. Apply thinly, otherwise details will be damaged.
Avoid inhibition
Sulfur, tin, amines
Additive silicones do not harden in contact with sulfur, tin, amines, or latex. Sticky areas will result. If in doubt, test compatibility or seal the surface.
System selection
Addition and condensation compared
The most important decision is the networking system. Both profiles serve as a guide; specific key figures can be found in the data sheet and the linked technical articles.
| Characteristic | Addition crosslinking (platinum) | Condensation crosslinking (tin) |
|---|---|---|
| Shrinkage | very low | moderate |
| Dimensional accuracy | very high | medium |
| Long-term stability | high | less |
| Inhibition risk | present (sulfur, tin, amines) | small amount |
| Food contact | possible (compliant types) | Generally, no |
| Potting time | adjustable | humidity-dependent |
| Price | higher | cheaper |
| Typical use | Precision, series production, food | large molds, single casting, 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 guideline
| Hardness (guideline value) | character | Typical application |
|---|---|---|
| soft, approximately 10 to 20 Shore A | highly elastic | deep undercuts, delicate negatives |
| medium, approximately 25 to 35 Shore A | All-round | Standard shapes, casting resins, architecture |
| hard, approximately 40 Shore A and higher | abrasion-resistant, surface-stable | Mass-produced parts, abrasive casting materials, large flat molds |
Hardness bands are guidelines. The specific type depends on the geometry, cycle time, and casting material and is listed in the data sheet.
Decision
Selection aid
| Requirement | More suitable | Notice |
|---|---|---|
| Maximum dimensional accuracy, fine details | Additive silicone (platinum), rather soft Shore | Note inhibition |
| Large format, budget, single casting | Condensation silicone (tin) | Plan for a little more shrinkage |
| Food, baking tins | food-grade platinum silicone | Conformity according to data sheet |
| Mass production, many castings | harder Shore, semi-permanent release agent | Ensure the mold's service life |
| Deep undercuts | soft Shore | Demolding without cracking |
| Pour polyurethane or polyester resin | Release agent, e.g. silicone spray | protects the mold surface |
| Tight deadlines, iterations | fast-curing types | short pot and demolding time |
| concrete, plaster | medium to hard Shore | elastic, sharp-edged demolding |
Key factors include the casting material, quantity, level of detail, dimensional tolerance, and food contact. Specific parameters are listed in the respective technical data sheet.
After application
Typical applications
Where silicone molds are needed in practice, and what the choice of material contributes to.
Architecture & Model Making
Sub-mm detail
Intricate facades, terrain, and shadow gaps; reproducible small series made of Acrystal or plaster. Precise and sharp-edged. Art & Model Making.
Art, Design & Jewelry
finest contours
Sculptures, reliefs, and jewelry casting with the highest level of detail. Precision types with minimal shrinkage reproduce the finest contours. Art & Model Making.
Mass production of castings
many casts
Repeatable castings in large quantities. Harder types and semi-permanent release agents ensure the mold's service life. Mechanical engineering.
Concrete & Plaster
Architecture, Decor
Molds and formwork for precast concrete, stucco, and decorative elements. Elastic demolding protects sharp edges and delicate profiles. Construction.
Food & Baking Pans
conforming types
Food-grade platinum silicone for baking, chocolate, and ice cream 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 making your selection
- Casting material: resin, concrete, plaster, wax or metal, and how reactive it is.
- Quantity: Single piece, small series or series, this determines the required mold lifespan.
- Level of detail and geometry: undercuts, delicate bridges, textures.
- Dimensional tolerance: how sensitive is the part to shrinkage?
- Food or skin contact: requires compliant types.
- Pot life, curing time and cycle time: adapted to the throughput.
- Shape size and wall thickness: influence material, hardness and stabilization.
- Release agent concept: dependent on casting material and quantity.
Using this information, we will jointly narrow down the system, hardness and release agent and check the data sheets.
processing
Process cleanly
- Prepare the model: clean, dry and grease-free, seal porous surfaces such as plaster or wood.
- Check for inhibition: when using 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, wipe the container walls.
- Degassing: in a vacuum or with a thin primer to prevent air inclusions.
- Giessen: thin stream at the lowest point, slowly, so that air rises.
- Demolding and post-hardening: Allow the mold to post-harden and condition it with a test casting before series production.
Note: Use only as much release agent as necessary; too thick a film will fill in fine details. A barrier layer is mandatory when applying silicone to silicone.
From practice
Common mistakes
- Inhibition: sticky, uncured zones due to contact with sulfur, tin, or amines.
- Air inclusions due to pouring too quickly or lack of degassing.
- Form cracking due to excessively soft Shore hardness or overly aggressive demolding.
- Distortion of large areas due to a system that is too soft and lacks 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-based or condensation-based?
Addition-curing (platinum) for precision, dimensional accuracy, food contact, and series production. Condensation-curing (tin) for large molds, individual castings, and tight budgets. The rule of thumb is shown in the comparison above.
Do I always need a release agent?
Not necessarily; silicone is often self-releasing. It becomes necessary when bonding silicone to silicone, with reactive resins like polyurethane, and with molds made of foreign materials. A preliminary test with the original materials is advisable.
Which Shore hardness is suitable?
Intricate objects and deep undercuts require softer grades, while flat and abrasive applications require harder grades. The hardness bands above are guidelines; the specific grade is listed in the datasheet.
How do I avoid inhibition?
When working with addition silicones, avoid contact with sulfur, tin, amines, and latex; separate work areas and seal porous or critical surfaces. If in doubt, test on a small area.
How many casts can one mold hold?
This depends on the material, hardness, casting material, and release agent, and ranges from a few to thousands of castings. Harder types and semi-permanent release agents increase the service life.
Are the silicones food-safe?
There are food-grade platinum alloys for baking and food molds. Specific compliance is product-dependent and indicated in the data sheet.
Further information
Matching products, worlds, articles & industries
Product groups: Silicone products · RTV-2 silicones (mold making) · Resins & potting solutions
Themed areas: Silicones · Mold making & molding
Knowledge article: 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: in the glossary (RTV-2, addition crosslinking, condensation crosslinking, Shore hardness, inhibition, release agent, pot life).
Technical basis: Information provided is for general guidance only and does not constitute a product guarantee. Manufacturer data sheets (TDS) and relevant standards are binding. Specific characteristics (Shore hardness, shrinkage, pot life, temperature range, conformity) are product-dependent.
contact
Unsure which mold-making system is right for your casting?
Describe the casting material, quantity, level of detail, and geometry. We will recommend the appropriate system, hardness, and release agent, review the technical data sheets, and deliver from our warehouse in Gümligen.