Description
This platinum-cure silicone rubber self-thickens for making brush-on molds of almost any model.
Rebound™ 25 is mixed 1A:1B by volume, to a gel like consistancy, allowing application with a brush or spatula to vertical surfaces without sagging. It cures with negligible shrinkage to a flexible rubber.
Features
- Soft and flexible, suitable for making molds of models with deep undercuts.
- Can be inverted as glove molds depending on model configuration.
- Compatible with harder, less flexible variants.
- Minimal surface preparation required as it does not stick to most surfaces.
- Stands up better to production casting of resins and low temperature melt metal alloys.
- Long library life, lasting many years in a mold library.
- Applications include reproducing sculpture, architectural restoration, making candle molds, casting pewter, etc.
- Not compatible with modeling clays containing sulfur.
Technical Properties
- Mix Ratio By Volume: 1A:1B
- Mix Ratio By Weight: 1A:1B
- Working time: 20 minutes
- Cure Time: 6 hours
- Shore Hardness: 25 A
- Specific Gravity: 1.14 g/cc
- Specific Volume: 0.88 cm³/g
- Color: Orange
- Tensile Strength: 3.55 MPa
- Elongation @ Break: 690%
- Die B Tear Strength: 17.9 kN/m
Instructions
Safety
Use in a properly ventilated area. Wear safety glasses, long sleeves, and
and vinyl gloves to minimize contamination risk. N.B. latex gloves will inhibit the cure of the rubber.
Storage and Use
Store and use at room temperature (23°C). Warmer temperatures reduce working and cure time.
Storing at cooler temperatures will extend the shelf life.
Cure Inhibition
Inhibition may occur with contaminants like latex, tin-cure silicone, sulfur clays, and certain wood surfaces. Test compatibility on a non-critical area.
Seal the object with a clear acrylic lacquer to prevent inhibition. Allow the sealer to dry before applying the rubber.
When in doubt, a small test application to determine suitability for your project is recommended.
When working with modeling clays that contain heavy amounts of sulfur, even a sealer will not suffice. Do a small scale test for compatibility before starting your project.
Applying A Release Agent
The use of a release agent is usually not necessary, but will help with the ease of demolding. Use Ease Release™ 200. Spray the object once, then brush lightly over the surface, spry once more lightly and let dry for 30 minutes.
Test on an identical surface if unsure.
Measuring & Mixing
Pre-mix Part A and Part B separately. Mix thoroughly after dispensing required amounts into a container (1A:1B by volume or weight), ensuring a uniform color with no streaks.
Applying The Rubber
Apply in layers. Four thin layers (minimum 9.5 mm thickness) are suitable for a strong mold. The first coat should be applied thinly to capture detail, using dabbing strokes to reduce air entrapment. Let each coat dry for 60 minutes at room temperature until the surface is tacky, before applying the next coat. This process can be accellerated with mild heat.
Coverage
1 gal. unit covers 0.65 sq.m and 5 gal. unit covers 3.25 sq.m.
Options
- Add different Silc-Pig™ color pigment to successive layers, to distinguish them.
- Thi-Vex™ thickener can be added to increase the thixotropy.
- Add Smooth-On Silicone Thinner™ to lower the viscosity of the initial mix.
Apply A Support Shell
Once fully cured, a rigid support shell is necessary. PlastiPaste™ II is ideal for this purpose.
Curing
Allow the mold to cure for at least 6 hours at room temperature before demolding. Do not cure rubber at temperatures below 18°C. Cure faster by applying mild heat (60°C) for 2 hours.
Using The Mold
When casting wax or gypsum, the use of a release agent is not necessary.
Apply a release agent like Ease Release™ 200 when casting polyurethane, polyester, and epoxy resins to prevent mold degradation.
Mold Performance & Storage
The physical life of the mold depends on it's usage. Casting abrasive materials can erode mold detail. Clean molds with a soap solution and dry before storing on a level surface in a cool, dry environment.
