RTV stands for "Room Temperature Vulcanizing". This means that the silicone will cure at room temperature, without the need of expensive oven heating. However, the higher the ambient temperature, the quicker RTV cures.

There are two basic types of silicone mold making products available. They are Polycondensation or Tin Cure and Polyaddition or Platinum Cure.

The Polyaddition/Platinum Cure is the most expensive of the two. It offers better mold stability and less shrinkage. However it is susceptible to inhibition from a wide variety of materials, and must be handled very precisely to produce a good cure.

Polycondensation/Tin Cure silicone is less expensive, has a virtually trouble-free cure, and is not sensitive to inhibition. This is the kind of silicone in TAP Silicone RTV System.

On the following pages you will see instructions using the Rhodorsil RTV2. Please note that even though the name is different, the instruction also applies to TAP Silicones. We hope you find these pages helpful in your mold making journey.

TAP Silicone RTV's are used in moulding are two-component, room temperature curing elastomers.

TAP Silicone RTV's silicone elastormers have specific properties which provide users with many advantages;

Flexibility
Easy to demould
Fine reproduction detail
High tear strength
Room temperature curing, no heat release
Easy to use, without any heavy equipment
Aging resistance
Heat stability
Dielectric properties
Low shrinkage
 
There are 2 different types of RTV2;
1. Polycondensation RTV2 (PC)
2. Polyaddition RTV2 (PA)

Polycondensation type TAP Platinum Silicone is supplied as base and catalyst, polyaddition type TAP Silicone RTV System is supplied as Part A and Part B.

Each of these types have specific features that means it must be chosen according to the user's requirements.

		POLYCONDENSATION RTV2		POLYADDITION RTV2
MIXING RATIO		100/2 - 100/10		100/10 - 100/100
SAFETY PRECAUTIONS DURING MIXING		Glasses and gloves are required, Well ventilated working area		None
POT LIFE / DEMOULDING TIME		Variable depending on the catalyst, Not heat accelerated		Can be independent, Heat accelerated
RISK OF INHIBITION		No		Yes
SENSITIVE TO REVERSION		Yes		No
SHRINKAGE		%0.8 - 1.2		D=%0.05 - 0.2

Curing starts once the two components are mixed at a rate that depends on the operating conditions. The ideal conditions are;
23°C ambient temperature
50% relative humidity

In order to comply with dimensions it is preferable to use;
moderate temp. 23 - 30°C and
in any case no less than 20°C
minimum 30% humidity
comply with the recommended
catalyst dosage

There are numerous moulding applications for SILICONE RTV's, a few of them are mentioned below.

EXAMPLES OF USE	MATERIAL
Furniture Figurines Reproduction of Statuettes Frames, Mirrors, Paintings Buttons Souvenirs Palaeontology Reproduction of Old Objects Various Decorative Items Prototypes Leather Goods Shoes Interior Car Trim Cornices Production of Tooling Staff Master Moulds for Tiles Ceramics Porcelain Decorative Candles Artistic Metalwork Jewellery	Polyester Polyurethane PVC Epoxies Concrete Plaster Wax - Paraffin Low Melting Point Alloys Acrylic Resins

Models are made in a wide range of materials whose surface conditions and porosity differ. Even though SILICONE RTV does not adhere to most materials, it is usual to take certain precautions before taking impressions. Various possibilities are offered below which are tested in laboratories.

TYPE OF MODEL RECOMMENDED TREATMENT Plaster, Concrete, Stone, Biscuit, Terracotta, etc. Remove dust and apply a pore filler from among the following:Polyvinyl alchol type 4/125 diluted Soap, dissolve 250g of glycerine soap in one liter of boiling water; use once cool Wax or parafin deposit (diluted to 5% in xylene) Vaseline deposit Varnishing; gum lacquer or cellulose or acrylic varnish Metal Degreasing with a solvent or washing with a water based solution made with 5% liquid detergent, then drying Wax Glass, Porcelain, Ceramics Apply a very thin coat of vaseline Leather Apply a very thin coat of vaseline Wax Wood Apply vaseline or wax, a cellulose pore filler or cellulose varnish Plastic Degrease with appropriate solvent for the plastic concerned RTV2 Apply a very thin coat of vaseline Wax Resins (Polyurethane, epoxy, polyester, acrylic, etc) Apply polyvinyl alcohol then a very thin coat of vaseline Wax Wax No treatment required

SILICONE RTV enable moulds to be made for all types of applications using a few basic principles. In spite of the multiple variants that are possible, basic processes exist which are described below.

MODEL FEATURES		MOULDING TECHNIQUE	APPLICATION TECHNIQUE	ADVANTAGES	DISADVANTAGES
	Flat back, few or no undercuts	One Part Block Moulding	Casting	Quick,easy to perform Self supporting moulds Low cost to produce	Limited to relatively simple shapes that do not vary much in cross section - Significant material consumption
	Fully structured, few or no undercuts	Two Part Block Moulding	Casting	Quick,easy to perform Self supporting moulds Low cost to produce	Limited to relatively simple shapes that do not vary much in cross section - Significant material consumption
	Flat back, accentuated undercuts   Fully structured, few or no undercuts	One Part Skin Moulding   Two Part Skin Moulding	Casting	Thin section membranes Economic in materials (RTV) Large degree of flexibility favouring difficult moulding operations Availability of tooling enabling the production of membranes	Longer to implement than the block moulding method Greater cost of production
	Little or accentuated undercuts, Voluminous model on base, On-site reproduction	One Side Impression Moulding (Brush Moulding)	Brush, Spatula, Spraying	- Possibility of taking the imprint on site - Possibility of taking vertical or overhanging imprints - Adapted to large dimension mouldings - Economic in materials (RTV) - Difficult to perform	- Membrane is not interchangeable between backing moulds - Longer to implement than the block moulding method
	Little or accentuated undercuts, Fully structured, Voluminous model that is not easy or that can not be moved	Two Part Impression Moulding (Brush Moulding)	Brush, Spatula, Spraying	- Possibility of taking the imprint on site - Possibility of taking vertical or overhanging imprints - Adapted to large dimension mouldings - Economic in materials (RTV) - Difficult to perform	- Membrane is not interchangeable between backing moulds - Longer to implement than the block moulding method

		Remix each of the two components of the SILICONE RTV everytime berfore using. Mix the two components in the recommended proportions.
		Mix by using either a spatula or a mechanical mixer on a low speed setting so as to limit the inclusion of air in the mixture, until a perfectly uniform mixture is obtained.
		Degasing The catalysed mixture is degased under a vacuum of 20-50 mbar. The RTV will expand under the action of the vacuum and it is therefore necessary to have a container of appropriate size. Degassing is not required for TAP Platinum Silicone. It's low viscosity provides easy bubble release.
		Degasing generally lasts several minutes and at least until the bubbles stop rising regularly to the surface when the vacuum is released. However, prolonged degasing can cause loss of certain components that are required for curing.